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# Apache IoTDB 2.0.2

## Features & Improvements

- Data Query: Added management of table model UDFs, including user-defined scalar functions (UDSF) and user-defined aggregate functions (UDAF).
- Data Query: Table model now supports permission management, user management, and authorization for related operations.
- Data Query: Introduced new system tables and various O&M statements to optimize system management.
- System Management: The tree model and table model are now fully isolated at the database level.
- System Management: The built-in MQTT Service is now compatible with the table model.
- System Management: The CSharp client now supports the table model.
- System Management: The Go client now supports the table model.
- System Management: Added a C++ Session write interface for the table model.
- Data Synchronization: The table model now supports metadata synchronization and synchronization delete operations.
- Scripts and Tools: The import-data/export-data scripts now support the table model and local TsFile Load.
- ...

## Bugs

- Fixed the memory leak issue when writing data using SQL.
- Fixed the issue of duplicate timestamps appearing in table model queries.
- Fixed the issue of duplicate removal anomaly in table model aggregate queries with GROUP BY.
- Fixed the handling of Long.MIN_VALUE or Long.MAX_VALUE during write and merge processes.
- Fixed the issue of Long.MIN_VALUE timestamp causing time partition overflow and subsequent load failure.
- Fixed the issue of out-of-order data within a single TSFile on the destination data node during region migration in load operations.
- Fixed the issue where Explain Analyze caused the execution plan to fail to properly perform column pruning.
- Fixed the issue where the C# Session could not correctly fetch result sets when querying large amounts of data (exceeding fetch_size) on a cluster with more than one node.
- Fixed the inconsistency in reading JDK environment variables by ConfigNode and DataNode on Windows.
- Fixed the issue where the query distribution time statistics in Explain Analyze were larger than actual values, and changed the query distribution time monitoring from FI level to Query level.
  ...

# Apache IoTDB 2.0.1-beta

## Features & Improvements

- Table Model: IoTDB has introduced a new model named table model, and supports standard SQL query syntax, including SELECT, WHERE, JOIN, GROUP BY, ORDER BY, LIMIT clause and subQuery.
- Data Query: The table model supports a variety of functions and operators, including logical operators, mathematical functions, and the time-series specific function DIFF, etc.
- Data Query: The databases of the table model and tree model are invisible to each other, and users can choose the appropriate model based on their needs.
- Data Query: Users can control the loading of UDF, PipePlugin, Trigger, and AINode via URI with configuration items to load JAR packages.
- Storage Engine: The table model supports data ingestion through the Session interface, and the Session interface supports automatic metadata creation.
- Storage Engine: The Python client now supports four new data types: String, Blob, Date, and Timestamp.
- Storage Engine: The comparison rules for the priority of same-type merge tasks have been optimized.
- Data Synchronization: Support for specifying authentication information of the receiving end at the sending end.
- Stream Processing Module: TsFile Load now supports the table model.
- Stream Processing Module: Pipe now supports the table model.
- System Management: The Benchmark tool has been adapted to support the table model.
- System Management: The Benchmark tool now supports four new data types: String, Blob, Date, and Timestamp.
- System Management: The stability of DataNode scaling down has been enhanced.
- System Management: Users are now allowed to perform drop database operations in readonly mode.
- Scripts and Tools: The import-data/export-data scripts have been extended to support new data types (string, binary large objects, date, timestamp).
- Scripts and Tools: The import-data/export-data scripts have been iterated to support the import and export of three types of data: TsFile, CSV, and SQL.
- Ecosystem Integration: Support for Kubernetes Operator.
  ...

## Bugs

- Fixed the issue where the query result set contained duplicate timestamps.
- Fixed the issue where deleted data could be queried again when triggered to merge after deletion.
- Fixed the issue where the target sequence in  SELECT INTO containing backticks would result in writing the wrong sequence.
- Fixed the issue where an array out-of-bounds exception was thrown in the HAVING clause of the tree model due to a non-existent column name.
- Fixed the issue where MergeReader needed to consider memory allocation to avoid negative available memory during out-of-order and reverse queries.
- Fixed the issue where the CN in the cluster could not register large pipe plugins (greater than 100MB) and the parameters were not configurable.
- Fixed the issue of controlling the memory size of TimeIndex referenced by Pipe for TsFileResource.
- Fixed the issue where the Storage Engine - File Count - mods displayed negative values on the monitoring dashboard.
- Fixed the issue where the query result order was incorrect in the C# client.

...

# Apache IoTDB 1.3.3

## Features & Improvements

- Storage Engine: Added new data types String, Blob, Date, and Timestamp.
- Storage Engine: Multi-level storage has added a rate-limiting mechanism.
- Storage Engine: New merge target file splitting feature, with additional configuration file parameters, and improved memory control performance of the merge module.
- Data Query: Filter performance optimization, enhancing the speed of aggregate queries and where condition queries.
- Data Query: New client query requests load balancing optimization.
- Data Query: New active metadata statistics query added.
- Data Query: Optimized memory control strategy during the query planning phase.
- Data Synchronization: The sender supports transferring files to a specified directory, and the receiver automatically loads them into IoTDB.
- Data Synchronization: The receiver has a new automatic conversion mechanism for data type requests.
- Data Synchronization: Enhanced observability on the receiver side, supporting ops/latency statistics for multiple internal interfaces, consolidated into a single pipeTransfer display.
- Data Loading: DataNode actively listens and loads TsFiles, with additional observability metrics.
- Stream Processing Module: New data subscription capability, supporting subscription to database data in the form of data points or tsfile files.
- Stream Processing Module: Alter Pipe supports the ability to alter the source.
- System Management: Optimized configuration files, with the original three configuration files merged into one, reducing user operational costs.
- System Management: Optimized restart recovery performance, reducing startup time.
- System Management: Internal addition of monitoring items such as device count, estimated remaining time for data synchronization, size of data to be synchronized, and synchronization speed.
- Scripts and Tools: The import-tsfile script is expanded to support running the script on a different server from the IoTDB server.
- Scripts and Tools: New metadata import and export scripts added.
- Scripts and Tools: New support for Kubernetes Helm added.
- AINode: AINode module added.
  ...

## Bugs

- Fixed the issue of NullPointerException (NPE) when merging chunks with modifications and empty pages in the sequential space.
- Fixed the issue where the wrong parent file was used when reassigning the file position for skipped files during merge, leading to failure in creating hard links.
- Fixed the issue where the newly added four data types had null values written, and the TsFile handling of the STRING type was incorrect, causing a BufferUnderflowException: null.
- Fixed the issue in the high availability scenario where stopping the DataNode resulted in a PipeException: Failed to start consensus pipe.
- Fixed the issue in Stream mode where the first batch of written data points might require a flush to be synchronized.
- Fixed the compatibility issue with pipe plugin upgrades.
- Fixed the issue where the `ORDER BY` clause became ineffective when used in combination with `LIMIT` in the last query.
  ...

# Apache IoTDB 1.3.2

## Features & Improvements

- Storage Module: Performance improvement in the insertRecords interface for writing
- Query Module: New Explain Analyze statement added (monitoring the time spent on each stage of a single SQL execution)
- Query Module: New UDAF (User-Defined Aggregate Function) framework added
- Query Module: New MaxBy/MinBy functions added, supporting the retrieval of maximum/minimum values along with the corresponding timestamps
- Query Module: Performance improvement in value filtering queries
- Data Synchronization: Path matching supports path pattern
- Data Synchronization: Supports metadata synchronization (including time series and related attributes, permissions, etc.)
- Stream Processing: Added Alter Pipe statement, supporting hot updates of plugins for Pipe tasks
- System Module: System data point count statistics now include statistics for data imported by loading TsFile
- Scripts and Tools: New local upgrade backup tool added (backing up original data through hard links)
- Scripts and Tools: New export-data/import-data scripts added, supporting data export in CSV, TsFile formats or SQL statements
- Scripts and Tools: Windows environment now supports distinguishing ConfigNode, DataNode, and Cli by window name
  ...
- 
## Bugs

- Optimize the error message when a NullPointerException (NPE) occurs due to a timeout when dropping a database.
- Add logs for notifyLeaderReady, notifyLeaderChanged, and procedure worker.
- Add compatibility handling for existing erroneous data during file merging.
- Fix the deadlock issue caused by flushing empty files during querying.
- Fix the issue where Ratis becomes unresponsive during read, write, and delete operations.
- Fix the concurrent bug in load and merge operations.
- Fix the issue where the system's compression ratio is recorded as a negative number in the file for certain scenarios.
- Fix the ConcurrentModificationException issue during memory estimation for merge tasks.
- Fix potential deadlocks that may occur when writing, automatically creating, and deleting databases concurrently.
  ...

# Apache IoTDB 1.3.1

## Features & Improvements
- Add cluster script for one-click start-stop (start-all/stop-all.sh & start-all/stop-all.bat)
- Add script for one-click instance information collection (collect-info.sh & collect-info.bat)
- Add new statistical aggregators include stddev and variance
- Add repair tsfile data command
- Support setting timeout threshold for Fill clause. When time beyond the threshold, do not fill value.
- Simplify the time range specification for data synchronization, directly set start and end times
- Improved system observability (adding dispersion monitoring of cluster nodes, observability of distributed task scheduling framework)
- Optimized default log output strategy
- Enhance memory control for Load TsFile, covering the entire process
- Rest API (Version 2) adds column type return.
- Improve the process of query execution
- Session automatically fetch all available DataNodes
  ...

# Apache IoTDB 1.3.0

## Bugs

- Fix issue with abnormal behavior when time precision is not in milliseconds during grouping by month.
- Fix issue with abnormal behavior when duration contains multiple units during grouping by month.
- Fix bug where limit and offset cannot be pushed down when there is an order by clause.
- Fix abnormal behavior in combination scenario of grouping by month + align by device + limit.
- Fix deserialization errors during IoT protocol synchronization.
- Fix concurrent exceptions in deleting timeseries.
- Fix issue where group by level in view sequences does not execute correctly.
- Fix potential issue of metadata creation failure when increasing election timeout

## Features & Improvements

- Optimize the permission module and support timeseries permission control
- Optimize heap and off-heap memory configuration in startup script
- Computed-type view timeseries support LAST queries
- Add pipe-related monitoring metrics
- Pipe rename 'Extractor' to 'Source' and 'Connector' to 'Sink'
- [IOTDB-6138] Support Negative timestamp
- [IOTDB-6193] Reject Node startup when loading configuration file failed
- [IOTDB-6194] Rename target_config_node_list to seed_config_node
- [IOTDB-6200] Change schema template to device template
- [IOTDB-6207] Add Write Point Metrics for load function
- [IOTDB-6208] Node error detection through broken thrift pipe
- [IOTDB-6217] When the number of time series reaches the upper limit, the prompt message should be changed to prioritize using device templates
- [IOTDB-6218] Rename storage_query_schema_consensus_free_memory_proportion to datanode_memory_proportion
- [IOTDB-6219] Fix the display problem of explain that the print result is not aligned
- [IOTDB-6220] Pipe: Add check logic to avoid self-transmission
- [IOTDB-6222] Optimize the performance of Python client
- [IOTDB-6230] Add HEAPDUMP configuration in datanode-env.sh
- [IOTDB-6231]SchemaCache supports precise eviction
- [IOTDB-6232] Adding SSL function to dn_rpc_port

# Apache IoTDB 1.2.2

## Bugs

- [IOTDB-6160] while using ` in target path, select into will throw error
- [IOTDB-6167] DataNode can't register to cluster when fetch system configuration throws NPE
- [IOTDB-6168] ConfigNode register retry logic does not worked
- [IOTDB-6171] NPE will be thrown while printing FI with debug on
- [IOTDB-6184] Merge Sort finishes one iterator too long
- [IOTDB-6191] Fix group by year not considering leap years
- [IOTDB-6226] Fix the problem of inaccurate GC monitor detection at the beginning and adjusting the alert threshold
- [IOTDB-6239] Show regions display error create time

## Features & Improvements

- [IOTDB-6029] Implementing flink-sql-iotdb-connector
- [IOTDB-6084] Pipe: support node-urls in connector-v1
- [IOTDB-6103] Adding count_time aggregation feature
- [IOTDB-6112] Limit & Offset push down doesn't take effect while there exist time filter
- [IOTDB-6115] Limit & Offset push down doesn't take effect while there exist null value
- [IOTDB-6120] push down limit/offset in query with group by time
- [IOTDB-6129] ConfigNode restarts without relying on Seed-ConfigNode
- [IOTDB-6131] Iotdb rest service supports insertRecords function
- [IOTDB-6151] Move DataNode's system.properties to upper dir
- [IOTDB-6173] Change default encoder of INT32 and INT64 from RLE to TS_2DIFF
- Adjust the default thrift timeout parameter to 60s
- Accelerate the deletion execution

## Bugs

- [IOTDB-6064] Pipe: Fix deadlock in rolling back procedures concurrently
- [IOTDB-6081] Pipe: use HybridExtractor instead of LogExtractor when realtime mode is set to log to avoid OOM under heavy insertion load
- [IOTDB-6145] Pipe: can not release TsFile or WAL resource after pipe is dropped
- [IOTDB-6146] Pipe: can not transfer data after 1000+ pipes' creating and dropping
- [IOTDB-6082] Improve disk space metrics
- [IOTDB-6104] tmp directory won't be cleaned after udf query end
- [IOTDB-6119] Add ConfigNode leader service check
- [IOTDB-6125] Fix DataPartition allocation bug when insert big batch data
- [IOTDB-6127] Pipe: buffered events in processor stage can not be consumed by connector
- [IOTDB-6132] CrossSpaceCompaction: The estimated memory size is too large for cross space compaction task
- [IOTDB-6133] NullPointerException occurs in unsequence InnerSpaceCompactionTask
- [IOTDB-6148] Pipe: Fixed the bug that some uncommited progresses may be reported
- [IOTDB-6156] Fixed TConfiguration invalidly in Thrift AsyncServer For IoTConsensus
- [IOTDB-6164] Can create illegal path through rest api
- Fix datanode status is ReadOnly because the disk is full
- Fix DataPartition allocation bug when insert big batch
- Fix flush point statistics
- Fix SchemaFileSketchTool is not found
- Refactoring DeleteOutdatedFileTask in WalNode
- Add compression and encoding type check for FastCompactionPerformer
- Add lazy page reader for aligned page reader to avoid huge memory cost when reading rows of aligned timeseries
- Pipe: use PipeTaskCoordinatorLock instead of ReentrantLock for multi thread sync
- Pipe: fix pipe procedure stuck because of data node async request forever waiting for response
- Pipe: fix NPE when HybridProgressIndex.updateToMinimumIsAfterProgressIndex after system reboot (DR: SimpleConsensus)
- Pipe: fix pipe coordinator deadlock causing CN election timeout
- Pipe: Improve performance for 10000+ pipes
- RATIS-1873. Remove RetryCache assertion that doesn't hold

# Apache IoTDB 1.2.1

## Features & Improvements

- [IOTDB-5557] The metadata query results are inconsistent
- [IOTDB-5997] Improve efficiency of ConfigNode PartitionInfo loadSnapshot
- [IOTDB-6019] Fix concurrent update of last query
- [IOTDB-6036] The mods file is too large, causing Query very slow even OOM problem
- [IOTDB-6055] Enable auto restart of the pipes stopped by ConfigNode because of critical exception
- [IOTDB-6066] Add ConfigNode timeslot metric
- [IOTDB-6073] Add ClientManager metrics
- [IOTDB-6077] Add force stop
- [IOTDB-6079] Cluster computing resource balance
- [IOTDB-6082] Improve disk space metrics
- [IOTDB-6087] Implement stream interface of Mods read
- [IOTDB-6090] Add memory estimator on inner space compaction
- [IOTDB-6092] Factor mods files into memory estimates for cross-space compaction tasks
- [IOTDB-6093] Add multiple validation methods after compaction
- [IOTDB-6106] Fixed the timeout parameter not working in thrift asyncClient
- [IOTDB-6108] AlignedTVList memory calculation is imprecise
-
## Bugs

- [IOTDB-5855] DataRegion leader Distribution is same as DataRegion Distribution
- [IOTDB-5860] Total Number of file is wrong
- [IOTDB-5996] Incorrect time display of show queries
- [IOTDB-6057] Resolve the compatibility from 1.1.x to 1.2.0
- [IOTDB-6065] Considering LastCacheContainer in the memory estimation of SchemaCacheEntry
- [IOTDB-6074] Ignore error message when TagManager createSnapshot
- [IOTDB-6075] Pipe: File resource races when different tsfile load operations concurrently modify the same tsfile at receiver
- [IOTDB-6076] Add duplicate checking when upsert alias
- [IOTDB-6078] fix timeChunk default compressType
- [IOTDB-6089] Improve the lock behaviour of the pipe heartbeat
- [IOTDB-6091] Add compression and encoding type check for FastCompactionPerformer
- [IOTDB-6094] Load：Fix construct tsFileResource bug
- [IOTDB-6095] Tsfiles in sequence space may be overlap with each other due to LastFlushTime bug
- [IOTDB-6096] M4 will output zero while meeting null
- [IOTDB-6097] ipe subscription running with the pattern option may cause OOM
- [IOTDB-6098] Flush error when writing aligned timeseries
- [IOTDB-6100] Pipe: Fix running in hybrid mode will cause wal cannot be deleted & some pipe data lost due to wrong ProducerType of Disruptor
- [IOTDB-6105] Load: NPE when analyzing tsfile

# Apache IoTDB 1.2.0

## New Feature

* [IOTDB-5567] add SQL for querying seriesslotid and timeslotid
* [IOTDB-5631] Add a built-in aggregation functions named time_duration
* [IOTDB-5636] Add round as built-in scalar function
* [IOTDB-5637] Add substr as built-in scalar function
* [IOTDB-5638] Support case when syntax in IoTDB
* [IOTDB-5643] Add REPLACE as a built-in scalar function
* [IOTDB-5683] Support aggregation function Mode for query
* [IOTDB-5711] Python API should support connecting multiple nodes
* [IOTDB-5752] Python Client supports write redirection
* [IOTDB-5765] Support Order By Expression
* [IOTDB-5771] add SPRINTZ and RLBE encodor and LZMA2 compressor
* [IOTDB-5924] Add SessionPool deletion API
* [IOTDB-5950] Support Dynamic Schema Template
* [IOTDB-5951] Support show timeseries/device with specific string contained in path
* [IOTDB-5955] Support create timeseries using schema template in Session API

## Improvements

* [IOTDB-5630] Make function cast a built-in function
* [IOTDB-5689] Close Isink when ISourceHandle is closed
* [IOTDB-5715] Improve the performance of query order by time desc
* [IOTDB-5763] Optimize the memory estimate for INTO operations
* [IOTDB-5887] Optimize the construction performance of PathPatternTree without wildcards
* [IOTDB-5888] TTL logs didn' t consider timestamp precision
* [IOTDB-5896] Failed to execute delete statement
* [IOTDB-5908] Add more query metrics
* [IOTDB-5911] print-iotdb-data-dir tool cannot work
* [IOTDB-5914] Remove redundant debug log in Session
* [IOTDB-5919] show variables add a variable timestamp_precision
* [IOTDB-5926] Optimize metric implementation
* [IOTDB-5929] Enable DataPartition inherit policy
* [IOTDB-5943] Avoid rpc invoking for SimpleQueryTerminator when endpoint is local address
* [IOTDB-5944] Follower doesn' t need to update last cache when using IoT_consensus
* [IOTDB-5945] Add a cache to avoid initialize duplicated device id object in write process
* [IOTDB-5946] Optimize the implement of tablet in Go client
* [IOTDB-5949] Support show timeseries with datatype filter
* [IOTDB-5952] Support FIFO strategy in DataNodeSchemaCache
* [IOTDB-6022] The WAL piles up when multi-replica iotconsensus is written at high concurrency


## Bug Fixes

* [IOTDB-5604] NPE when execute Agg + align by device query without assigned DataRegion
* [IOTDB-5619] group by tags query NPE
* [IOTDB-5644] Unexpected result when there are no select expressions after analyzed in query
* [IOTDB-5657] Limit does not take effect in last query
* [IOTDB-5700] UDF query did not clean temp file after the query is finished
* [IOTDB-5716] Wrong dependency when pipeline consumeOneByOneOperator
* [IOTDB-5717] Incorrect result when querying with limit push-downing & order by time desc
* [IOTDB-5722] Wrong default execution branch in PlanVisitor
* [IOTDB-5735] The result of adding the distinct function to the align by device is incorrect
* [IOTDB-5755] Fix the problem that 123w can not be used in Identifier
* [IOTDB-5756] NPE when where predicate is NotEqualExpression and one of subExpression is not exist
* [IOTDB-5757] Not Supported Exception when use like ' s3 || false' in where even Type of s3 is Boolean
* [IOTDB-5760] Query is blocked because of no memory
* [IOTDB-5764] Cannot specify alias successfully when the FROM clause contains multiple path suffixes
* [IOTDB-5769] Offset doesn' t take effect in some special case
* [IOTDB-5774] The syntax that path nodes start or end with a wildcard to fuzzy match is not supported
* [IOTDB-5784] Incorrect result when querying with offset push-down and time filter
* [IOTDB-5815] NPE when using UDF to query
* [IOTDB-5837] Exceptions for select into using placeholders
* [IOTDB-5851] Using limit clause in show devices query will throw NPE
* [IOTDB-5858] Metric doesn' t display the schemaCache hit ratio
* [IOTDB-5861] Last quey is incomplete
* [IOTDB-5889] TTL Cannot delete expired tsfiles
* [IOTDB-5897] NullPointerException In compaction
* [IOTDB-5905] Some aligned timeseries data point lost after flush
* [IOTDB-5934] Optimize cluster partition policy
* [IOTDB-5953] LastCache memory control param does not take effect
* [IOTDB-5963] Sometimes we may get out-of-order query result
* [IOTDB-6016] Release file num cost after cross compaction task


# Apache IoTDB 1.1.2
## New Feature

* [IOTDB-5919]show variables add a variable timestamp_precision
* Add Python SessionPool

## Improvement/Bugfix

* [IOTDB-5901] Load: load tsfile without data will throw NPE
* [IOTDB-5903] Fix cannot select any inner space compaction task when there is only unsequence data
* [IOTDB-5878] Allow ratis-client retry when gRPC IO Unavailable
* [IOTDB-5939] Correct Flusing Task Timeout Detect Thread
* [IOTDB-5905] Fix aligned timeseries data point lost after flushed in some scenario
* [IOTDB-5963] Make sure that TsBlock blocked on memory is added in queue before the next TsBlock returned by root operator
* [IOTDB-5819] Fix npe when booting net metrics
* [IOTDB-6023] Pipe: Fix load tsfile error while handling empty value chunk
* [IOTDB-5971] Fix potential QUOTE problem in iotdb reporter
* [IOTDB-5993] ConfigNode leader changing causes lacking some DataPartition allocation result in the response of getOrCreateDataPartition method
* [IOTDB-5910] Fix compaction scheduler thread pool is not shutdown when aborting compaction
* [IOTDB-6056] Pipe: Failed to load tsfile with empty pages (NPE occurs when loading)
* [IOTDB-5916]Fix exception when file is deleted during compaction selection
* [IOTDB-5896] Fix the NPE issue when taking snapshot in WAL combined with Aligned Binary
* [IOTDB-5929] Enable DataPartition inherit policy
* [IOTDB-5934] Optimize cluster partition policy
* [IOTDB-5926] Remove Useless Rater in Timer
* [IOTDB-6030] Improve efficiency of ConfigNode PartitionInfo takeSnapshot
* [IOTDB-5997] Improve efficiency of ConfigNode PartitionInfo loadSnapshot
* Fix potential deadlock when freeing memory in MemoryPool
* Release resource of FI after all drivers have been closed
* Set default degree of parallelism back to the num of CPU
* Make SequenceStrategy and MaxDiskUsableSpaceFirstStrategy are allowed in cluster mode
* Fix npe exception when invalid in metric module
* Fix CQ does not take effect in ns time_precision
* Fix storage engine memory config initialization
* Fix template related schema query
* add default charset setting in start-datanode.bat and print default charset when starting
* Fix TsfileResource error after delete device in sequence working memtable
* load TsFile bugs: Not checking whether the tsfile data loaded locally is in the same time partition during the loading process & LoadTsFilePieceNode error when loading tsfile with empty value chunks
* Fix alias query failure after restarting DataNode

# Apache IoTDB 1.1.1
## New Feature

* [IOTDB-2569] ZSTD compression

## Improvement/Bugfix

* [IOTDB-5781] Change the default strategy to SequenceStrategy
* [IOTDB-5780] Let users know a node was successfully removed and data is recovered
* [IOTDB-5735] The result of adding the distinct function to the align by device is incorrect
* [IOTDB-5777] When writing data using non-root users, the permission authentication module takes too long
* [IOTDB-5835] Fix wal accumulation caused by datanode restart
* [IOTDB-5828] Optimize the implementation of some metric items in the metric module to prevent Prometheus pull timeouts
* [IOTDB-5813] ConfigNode restart error due to installSnapshot failed
* [IOTDB-5657] Limit does not take effect in last query
* [IOTDB-5717] Incorrect result when querying with limit push-downing & order by time desc
* [IOTDB-5722] Wrong default execution branch in PlanVisitor
* [IOTDB-5784] Incorrect result when querying with offset push-down and time filter
* [IOTDB-5815] NPE when using UDF to query
* [IOTDB-5829] Query with limit clause will cause other concurrent query break down
* [IOTDB-5824] show devices with * cannot display satisfied devices
* [IOTDB-5831] Drop database won't delete totally files in disk
* [IOTDB-5818] Cross_space compaction of Aligned timeseries is stucked
* [IOTDB-5859] Compaction error when using Version as first sort dimension
* [IOTDB-5869] Fix load overlap sequence TsFile

# Apache IoTDB 1.1.0

## New Features

* [IOTDB-4572] support order by time in align by device
* [IOTDB-4816] Support Show Queries command
* [IOTDB-4817] Support kill query command
* [IOTDB-5077] Support new command formats in  SHOW REGIONS
* [IOTDB-5108] Support region migration
* [IOTDB-5202] Support show regions with specific database
* [IOTDB-5282] Add SQL show variables, which can display the current cluster variables
* [IOTDB-5341] Support GROUP BY VARIATION in aggregation query
* [IOTDB-5372] Support data type cast in SELECT INTO
* [IOTDB-5382] Support DIFF as built-in scalar function in IoTDB
* [IOTDB-5393] Show Region creation time when execute show regions
* [IOTDB-5456] Implement COUNT_IF built-in aggregation function
* [IOTDB-5515] Support GROUP BY CONDITION in aggregation query
* [IOTDB-5555] Enable modify dn_rpc_port and dn_rpc_address in datanode-engine.properties 
* Support docker deployment 
* Rename SeriesSlotId to SeriesSlotNum in show regions

## Improvements

* [IOTDB-4497] Improve NodeStatus definition
* [IOTDB-5066] Upgraded the GetSlots SQLs
* [IOTDB-5161] Add output type check for WHERE & HAVING clause and refuse expressions whose return type are not boolean exist in WHERE & HAVING clause
* [IOTDB-5185] Fixed that old snapshot is not deleted in IoTConsensus
* [IOTDB-5287] Added status “Discouraged” to RegionGroup
* [IOTDB-5449] Wait for query resource while the query queue is full instead of throwing exception directly 
* change STARTUP_RETRY_INTERVAL_IN_MS from 30s to 3s

## Bug Fixes

* [IOTDB-4684] Fix devices with the same name but different alignment properties are compacted into the wrong alignment property
* [IOTDB-5061] Add initialize state check when create snapshot
* [IOTDB-5090] Fix the NPE when executing stop-datanode.sh
* [IOTDB-5112] Fixed IoTConsensus synchronization stuck under low load or during restart
* [IOTDB-5126] Fix that show-regions show IP rather than hostname even though the hostname is used when registering
* [IOTDB-5165] Fix fail to pass compaction validation when resources degrade to FileTimeIndex
* [IOTDB-5170] Fix the problem that datanode is closed when executing stop-confignode.bat on Windows platform
* [IOTDB-5199] Fix NPE in StorageExector inLoading process
* [IOTDB-5216] Fix order by timeseries doesn't take effect in aligned last query
* [IOTDB-5228] NPE if the file does not exist while creating TsFileSequenceReader instance
* [IOTDB-5240] Fix schema template timeseries read/write error after restart
* [IOTDB-5245] Fix data is incomplete in last query
* [IOTDB-5277] Fix DataNode restart failure when SchemaRegion loading snapshot
* [IOTDB-5278] Fix JDBC Driver cannot connect to the dbeaver
* [IOTDB-5285] Fix TimePartition error when restarting with different time partition configuration
* [IOTDB-5269] Fix wrong data of devices ought to be deleted after executing `delete from` sql
* [IOTDB-5324] Fix wal cann't be deleted in destDataNode after region migration when data_replication_factor is 1 in IoTConsensus
* [IOTDB-5389] Cause DataNode startup to fail when wal_mode is disabled in IoTConsensus
* [IOTDB-5414] Fix timeseries with alias deleted success but can still be queried by alias
* [IOTDB-5426] Cannot trigger flush for sequence file when timed flush enabled
* [IOTDB-5441] Fix NPE while fetch schema that is not in template used by related device
* [IOTDB-5469] Fix get schema info failure after creating template with backquote characters successfully
* [IOTDB-5474] Fix count nodes using level bug
* [IOTDB-5480] IoTConsensus sync lag may be negative under single copy
* [IOTDB-5488] Support set system to readonly on local
* [IOTDB-5492] Skip broken tsfile when recovering system
* [IOTDB-5512] Fixed IoTConsensus may repeatedly send some log when restarting
* [IOTDB-5516] Fix creating timeseries failure after dropping all databases
* [IOTDB-5526] Fix deleting timeseries failure when it belongs to a device activating template
* [IOTDB-5548] Fix dropping template failure when using pure number as template name
* [IOTDB-5592] Fix unexpected error while using full path(starting with root) in having/where clause
* [IOTDB-5620] Fix flush stuck when there is a lot of time partitions in each DataRegion
* [IOTDB-5639] Fix file not found exception in cross space compaction selector
* [IOTDB-5657] Fix LIMIT&OFFSET does not take effect in last query
* [IOTDB-5684] Fix log folder generation when using ConfigNode's Simple consensus protocol
* [IOTDB-5685] Fix error msg of failing to create a timeseries on an existing path when ReadOnly state
* [IOTDB-5686] Fix devices with the same name but different alignment properties meets error in inner seq compaction
* [IOTDB-5700] Clean temporary files created by UDF query after it finishes 
* Add SHOW_CQ privilege

# Apache IoTDB 1.0.0

## New Features

* New architecture that supports standalone and cluster mode with two types of nodes: ConfigNode, DataNode
* Support ConfigNode management: Start/Add, Stop, Remove
* Support DataNode management: Start/Add, Stop, Remove
* Support replication of ConfigNode, Schema and Data
* Support Consensus Protocol: Simple, IoT, Ratis
* Support Cluster management sql: show cluster, show regions
* Support administration in Cluster:  User, Permission, Role management
* Support authorization when login and executing a command
* Support create/show/count/delete database
* Support show/count devices
* Support create/show/count timeseries
* Support schema template management
* Support MPP(massively parallel process) framework in cluster
* Support insertion, deletion and all query types in Cluster
* Support CSV import/export tools
* Support TsFile import/export tools
* Support Sync TsFile from an IoTDB with one replica to another with any replica number
* Support UDF framework in Cluster
* Support new UDF 'change_points
* Support stateful, stateless Trigger in Cluster
* Support Select into in Cluster
* Support Continuous Query in Cluster
* Support flush on local/cluster
* Support clear cache on local/cluster
* Support metric for DataNode and ConfigNode with output to IoTDB, Prometheus, and JMX
* Support DBAPI in python client
* Support RestApi, MQTT for cluster
* Support having clause and between expression in query
* Support order by timeseries in last query
* Support hot configuration of data_dirs

# Apache IoTDB 0.13.3

## Improvements

* [IOTDB-4525] Accelerate restart process
* [IOTDB-3164] Add compaction memory control
* [IOTDB-4364] Reduce read amplification in compaction
* [IOTDB-4424] Specify error message when time value of insert sql can not be correctly parsed
* [IOTDB-4492] Control total file size of cross space compaction task
* [IOTDB-4542] Optimize schema validate error message
* Optimize pattern matching in Regexp

## Bug Fixes

* [IOTDB-3988] Fix reload problem of metric module and refactor metric module
* [IOTDB-4239] fix NPE to insert a null value into a TEXT timeseries
* [IOTDB-4318] Fix RESTAPI data type conversion failed
* [IOTDB-4320] Fix insert row with null cause recover throw NPE
* [IOTDB-4343] Fix NPE when using MQTT protocol
* [IOTDB-4357] fix start in windows, IOTDB_LOG_DIR_IS_UNDEFINED folder appears
* [IOTDB-4585] Incorrect query result after deleting data for aligned timeseries
* [IOTDB-4615] TTL adapts timestamp precision
* [IOTDB-4636] IndexOutOfBoundsException when compacting aligned series
* Fix PathAlreadyExistException during concurrent auto creating aligned timeseries

# Apache IoTDB 0.13.2

## Improvements

[IOTDB-2669] Improve C++ client insertTablet performance
[IOTDB-3087] enlarge default value of avg_series_point_number_threshold
[IOTDB-3861] Enable insert null values in Session
[IOTDB-3996] REST API nonQuery support Continuous Query
[IOTDB-4120] Optimize memory allocation of Expression
[IOTDB-4190] update documents about nifi-iotdb-bundle
REST support "select into" in nonQuery API
Import-CSV supports specify data type and no need quotation for text value

## Bug Fixes

[IOTDB-2736] DELETE_STORAGE_GROUP can not be granted to user (reporting 401)
[IOTDB-2760] Ordinary users do not grant any permissions, but can still show operations
[IOTDB-2769] Fix auth mapping of GRANT_ROLE_PRIVILEGE and GRANT_USER_ROLE
[IOTDB-3302] Without any authorization, ordinary users still have the right to query other user information
[IOTDB-4023] The C++ interface query result returns records error
[IOTDB-4047] Query NPE after change device alignment
[IOTDB-4096] Fix the names of metric pushed to Prometheus are inconsistency in micrometer and dropwizard
[IOTDB-4194] IOException happened in Compaction
[IOTDB-4215] Fix incorrect aggregate query results due to wrong unseq file traversal order
[IOTDB-4216] Fix execute create aligned timeseries but a non-aligned timeseries created
[IOTDB-4222] DeadLock when concurrently deleting and creating storage groups
[ISSUE-6774] Connection error when using DataGrip with JDBC driver
[ISSUE-6937] After restart, the aligned series turns to non-aligned
[ISSUE-6987] Fix select error when selecting a single quotation mark

# Apache IoTDB 0.13.1

## New Features

* [IOTDB-2602] "Without null" supports filtering based on partial columns
* [IOTDB-3873] Aligned timeseries support single point fill query
* [ISSUE-6171] Support createTimeseriesOfTemplate in Session
* [IOTDB-3742] Support COUNT NODES by root.**

## Improvements

* [IOTDB-2820] Update UserGuide SQL about Trigger
* [IOTDB-2837] Add check and sort for NumpyTablet to make sure timestamps are ordered
* [IOTDB-2838] Check and auto correct endian type for NumpyTablet
* [IOTDB-2873] provide json template for grafana
* [IOTDB-2888] Unary expression can followed by a constant
* [IOTDB-3747] Default Paging of Schema Query with limit 10000
* [IOTDB-3797] Print detailed info in session when connection fails
* [IOTDB-3851] C++ client method of tablet sorting optimization
* [IOTDB-3879] Modify document about the Programming-Cpp-Native-API
* [IOTDB-3901] C++ client method of insertRecordsOfOneDevice sorting optimization

## Bug Fixes

* [IOTDB-2753] Insert a time series with a null value and report 500
* [IOTDB-2759] Result of "Show paths set schema template" or "using template" is not complete
* [IOTDB-2775] Fix throwing exception when query non-exist device in TsFileSequenceReader
* [IOTDB-2787] Fix aligned mem chunk concurrent problem
* [IOTDB-2826] Fix can not drop schema template
* [IOTDB-2828] Update system_version in system.properties after upgrading
* [IOTDB-2835] Fix empty page in selfcheck method of TsFileSequenceReader
* [IOTDB-2837] Add check and sort for NumpyTablet to make sure timestamps are ordered
* [IOTDB-2852] The import-csv tool can not import the data to nonaligned device
* [IOTDB-2859] Fix python tablet with None value is incorrect
* [IOTDB-2862] Fix SQL injection risks of grafana-connector
* [IOTDB-2864] Fix Read-only occurred when insert Text value to aligned timeseries
* [IOTDB-2882] Fix unary expression display bug
* [IOTDB-2902] Handling user privileges for aligned timeseries related features
* [IOTDB-2903] Fix show latest timeseries result does not sorted by time
* [IOTDB-2910] Fix count result not right after deleting storage group
* [IOTDB-2915] MLogTxtWriter error while parsing CreateAlignedTimeseriesPlan
* [IOTDB-2922] Fix NPE when compacting with files that contains zero device
* [IOTDB-2924] UDF Framework: index overflow while iterating sliding windows
* [IOTDB-2983] Serialization error in Partial insert
* [IOTDB-2999] Remove useless config and fix default value error.
* [IOTDB-3018] Fix compaction bugs on handling deleted target file
* [IOTDB-3029] The prefix path generated by the select into target sequence contains * and ** currently unchecked
* [IOTDB-3045] The query result contains some timeseries that have been deleted
* [IOTDB-3120] Print the tsfile name when meet IOException
* [IOTDB-3158] Fix NPE exception when use iotdb-reporter
* [IOTDB-3160] TsFile will be corrupted when flushing memtable appears OOM
* [IOTDB-3168] Forbid the path with * could be inserted
* [IOTDB-3171] Fix NPE when getting modification file
* [IOTDB-3219] Fix stop-server on windows
* [IOTDB-3247] Recover aligned sensors after deleting timeseries, query lost data
* [IOTDB-3301] Tag recover bug after IoTDB server restart
* [IOTDB-3364] Fix Query stucked with null valued aligned timeseries bug
* [IOTDB-3420] Fix show paths set schema template t1 error
* [IOTDB-3494] Fix TypeError in py-session
* [IOTDB-3523] Fix the count and COUNT not equal bug when querying with group by level
* [IOTDB-3645] Fix use statistics bug in aggregation query
* [IOTDB-3651] Stop compaction schedule when all compaction is disable
* [IOTDB-3709] Fix a loop occurred in TsFileResourceList, causing the query to fail and oom occurs
* [IOTDB-3730] Fix ArrayIndexOutOfBounds when flushing a memtable
* [IOTDB-3795] Remove setting read-only when handling compaction exception
* [IOTDB-3803] failed to insert data of TEXT by session
* [IOTDB-3816] Fix /zero bug in recover
* [IOTDB-3822] Fix cross compaction overlap bug
* [IOTDB-3826] Fix duplicate success when concurrent creating same timeseries
* [IOTDB-3858] IndexOutOfBoundsException: bitIndex < 0
* [ISSUE-5482] Fix Release zip files include incorrect version of Guava
* [ISSUE-5773] Aggregation result is not complete
* [ISSUE-5964] Fix bug of aligned timeseries time duplicated aggregation


# Apache IoTDB 0.13.0

## New Features

* [IOTDB-924] Support insert multi rows in SQL
* [IOTDB-959] Add Create Storage Group Grammar 
* [IOTDB-1037] set rpc\_compression as a parameter in JDBC URL
* [IOTDB-1059] Support sql statement insert without timestamp
* [IOTDB-1143] Support Continuous query
* [IOTDB-1199] Support aligned timeseries and schema template 
* [IOTDB-1319] Support Trigger
* [IOTDB-1391] Add a new Aggregation function extreme (max absolute value)
* [IOTDB-1399] Add a session interface to connect multiple nodes
* [IOTDB-1400] Support arithmetic operations in SELECT clauses
* [IOTDB-1403] Dictionary encoding for TEXT
* [IOTDB-1490] Add built-in UDTFs: sinh, conh, tanh
* [IOTDB-1514] Support null in insertTablet
* [IOTDB-1524] Support SELECT ... INTO ... clause 
* [IOTDB-1647] Nested Expressions in SELECT clauses
* [IOTDB-1673] CLI upgrade to JLine3
* [IOTDB-1739] Constant timeseries generating functions (const, pi and e) 
* [IOTDB-1760] Support avg, count, extreme, first\_value, last\_value, max\_time, max\_value, min\_time, min\_value, sum aggregations in group by fill
* [IOTDB-1761] Add metric framework for IoTDB
* [IOTDB-1775] Add CAST function to convert data type
* [IOTDB-1823] Support group by multi level
* [IOTDB-1844] Query support timeseries prefix and suffix matching: root.\*sg\*
* [IOTDB-1859] Support REST API
* [IOTDB-1860] New Grafana plugin
* [IOTDB-1886] Support Constant Expressions in Select Clauses
* [IOTDB-1973] Supports aggregate queries, constants, and arithmetic nested expressions in SELECT clauses
* [IOTDB-1986] Support select UDF as alisa clauses 
* [IOTDB-1989] Spark-IoTDB-connector support inserting data
* [IOTDB-2131] Support previous, linear, constant value fill funtion New fill
* [ISSUE-3811] Provide a data type column for the last query dataset
* add rabbitmq example

## Improvements

* [IOTDB-1280] Rewrite the Antlr grammar file
* [IOTDB-1372] Enhance management of TsFileResource 
* [IOTDB-1428] Ask query threads to quit if query is timeout 
* [IOTDB-1450] Deletion should only delete related time partitions
* [IOTDB-1463] Implement builder pattern for Session and SessionPool 
* [IOTDB-1477] Optimize code logic of generateAlignByDevicePlan() 
* [IOTDB-1559] Refactor the IT framework
* [IOTDB-1564] Make hearbeat and election timeout parameters be configurable
* [IOTDB-1581] Consider deletions when recovering tsFileResource of incomplete tsfile 
* [IOTDB-1607] Optimize Tracing
* [IOTDB-1613] Recover mods file if  write modification failed
* [IOTDB-1639] Refactoring the cluster class structure to make it consistent with the server module 
* [IOTDB-1730] client-cpp, enhance session::insertTablet() etc.'s performance 
* [IOTDB-1852] Accelerate queryies by using statistics
* [IOTDB-1857] Remove useless handle logic for CountPlan in executeNonQuery in cluster module
* [IOTDB-1884] Distinguish between zero and null values in sum aggregation
* [IOTDB-1924] Remove the operation of clearing the cache after the compaction is over
* [IOTDB-1950] Add Bloom Filter cache for query 
* [IOTDB-2001] Remove redundant StorageGroupNotReadyException
* [IOTDB-2011] Update last cache while doing show latest timeseries query
* [IOTDB-2022] SessionDataSet implements AutoCloseable
* [IOTDB-2075] Accelerate the process of insertTablets by using thread pool
* [IOTDB-2119] IoTDB CSV export tools add timestamp accuracy setting function 
* [IOTDB-2162] Simplify the recovery merge process
* [IOTDB-2176] Limit target chunk size when performing inner space compaction
* [IOTDB-2193] Reduce unnecessary lock operations of RaftLogManager to improve writing performance 
* [IOTDB-2195] Control the concurrent query execution thread
* [IOTDB-2632] Set compaction_write_throughput_mb_per_sec to 16 by default
* [ISSUE-3445] New compaction strategy and compaction scheduling strategy
* [ISSUE-3856] refine exception handling logic in commitTo in RaftLogManager
* [Cluster] No need to shake hands with itself when one node restart 


## Incompatible changes

* [IOTDB-1026] Support wildcard \*\* in Path And Replace PrefixPath usage with PathPattern in IOTDB-SQL
* [IOTDB-1620] Support backtick (\`) character and double quotes (") to quote identifiers 
* [IOTDB-1650] Rename the sql command `move` to `unload` 

## Miscellaneous changes

* [IOTDB-1342] modify error message about LIMIT and OFFSET used in conjunction with the FILL clause
* [IOTDB-1372] delete devices field in FileTimeIndex 
* [IOTDB-1531] Check tsfile creation time when recovering
* [IOTDB-1541] Change sequence of wal and memtable in insertion
* [IOTDB-1923] Separate the request unpacking and execution processing logic of TSServiceImpl
* [IOTDB-1969] Remove statistic resources of old metric framework from iotdb-server
* [IOTDB-2014] MicrometerPrometheusReporter#getReporterType return null 
* [IOTDB-2043] refactor: remove haveSorted param from Session
* [IOTDB-2154] add TsFileUtils.isTsFileComplete
* [IOTDB-2206] Rename StorageGroupProcessor to VirtualStorageGroupProcessor
* [IOTDB-2208] Reconstruct the process of generating resultset header of query
* [ISSUE-4047] Generic type in Statistics extend Serializable 
* Add compaction version in cache key
* Add a constructor of IoTDBDescriptorHolder to prohibit instantiation

## Bug Fixes

* [IOTDB-1266] Fix SHOW TIMESERIES will only display 2000 timeseries
* [IOTDB-1478] The whole IoTDB can not read/write if any one sg is not ready
* [IOTDB-1562] Fix incorrect exception processing in insertXXX() API
* [IOTDB-1583] Raft log failed to be committed in cluster version 
* [IOTDB-1592] BugFix: SLimit Not effective in align by device 
* [IOTDB-1736] Fix error code is not printed in TSServiceImpl's log 
* [IOTDB-1749] sync-tool's lockInstance() dose not take effect
* [IOTDB-1758] sync-tool, empty uuid file cause tool can not auto-recovery
* [IOTDB-1848] Failed to initialize pool: Does not support setReadOnly in grafana-connector
* [IOTDB-1853] Fix bug about more than one TimeseriesMetadata in TsFile
* [IOTDB-2010] fix incomplete show timeseries result
* [IOTDB-2021] Fix Bloom Filter Cache doesn't take effect bug 
* [IOTDB-2060] Fix NPE when using fill without a filter
* [IOTDB-2074] Fix NullPointerException when recovering compaction in MacOS
* [IOTDB-2077] Unexpected exception when executing raw data query without VF with limit clause
* [IOTDB-2088] Fix IndexOutOfBound exception in AggregationPlan.groupAggResultByLevel
* [IOTDB-2116] Fix all client connections are stuck bug caused by logback bug 
* [IOTDB-2129] Wrong result returned when querying by nested expressions with aliases
* [IOTDB-2143] fix wrong precision in cluster mode
* [IOTDB-2153] [IOTDB-2157] fix incorrect path search space 
* [IOTDB-2159] Fix wrong status code when inserting data to a read-only cluster
* [IOTDB-2163] Fix unexpected amount of columns in a cluster slimit query
* [IOTDB-2174] Fix Regexp filter serializing and deserializing error 
* [IOTDB-2180] Fix show latest timeseries in cluster
* [IOTDB-2183] Fix the config problems in cluster mode
* [IOTDB-2185] Fix get an exception when parsing the header of CSV
* [IOTDB-2209] Fix logback CVE-2021-42550 issue
* [IOTDB-2251] [IOTDB-2252] Fix Query deadlock 
* [IOTDB-2267] UDF: Error code 500 caused by user logic
* [IOTDB-2282] fix tag recovery bug after tag upsert
* [IOTDB-2290] Fix Incorrect query result in C++ client 
* Fix CPP client could not be successfully built on windows
* Fix dead lock in setDataTTL method


# Apache IoTDB 0.12.5

## New Features
* [IOTDB-2078] Split large TsFile tool
* [IOTDB-2192] Support extreme function

## Improvements
* [IOTDB-1297] Refactor the memory control when enabling time partitions
* [IOTDB-2195] Control the concurrent query execution thread
* [IOTDB-2475] Remove sg not ready log in batch process
* [IOTDB-2502] Add query sql in error log if encountering exception
* [IOTDB-2506] Refine the lock granularity of the aggregation query
* [IOTDB-2534] add character support while using double quote
* [IOTDB-2562] Change default value of sync mlog period parameter
* Avoid too many warning logs being printed, when opening too many file handlers


## Bug Fixes
* [IOTDB-1960] Fix count timeseries bug in cluster mode
* [IOTDB-2174] Fix Regexp filter serializing and deserializing error
* [IoTDB-2185] fix get an exception bug when parsing the header of CSV
* [IOTDB-2194] Fix SHOW TIMESERIES will only display 2000 timeseries in cluster mode
* [IOTDB-2197] Fix datatype conversion exception in Spark Connector
* [IOTDB-2209] Fix logback CVE-2021-42550 issue
* [IOTDB-2219] Fix query in-memory data is incorrect in cluster mode
* [IOTDB-2222] Fix OOM and data was written in incorrectly bugs of Spark Connector
* [IOTDB-2251] [IOTDB-2252] Fix Query deadlock
* [IOTDB-2282] fix tag recover bug after tag update
* [IOTDB-2320] MemoryLeak cause by wal Scheduled trim task thread
* [IOTDB-2381] Fix deadlock caused by incorrect buffer pool size counter
* [IOTDB-2400] Fix series reader bug
* [IOTDB-2426] WAL deadlock caused by too many open files
* [IOTDB-2445] Fix overlapped data should be consumed first bug
* [IOTDB-2499] Fix division by zero error when recovering merge
* [IOTDB-2507] Fix NPE when merge recover
* [IOTDB-2528] Fix MLog corruption and recovery bug after killing system
* [IOTDB-2532] Fix query with align by device can't get value after clear cache
* [IOTDB-2533] Fix change max_deduplicated_path_num does not take effect
* [IOTDB-2544] Fix tag info sync error during metadata sync
* [IOTDB-2550] Avoid show timeseries error after alter tag on sync sender
* [IOTDB-2567]  Fix thread and ByteBuffer leak after service stopped
* [IOTDB-2568] "show query processlist" is blocked
* [IOTDB-2580] Fix DirectByteBuffer and thread leak when deleting storage group
* [IOTDB-2584] Fix cross space compaction selector
* [IOTDB-2603] Fix compaction recover
* [IOTDB-2604] Fix batch size is invalid in import-csv tool
* [IOTDB-2620] Unrecognizable operator type (SHOW) for AuthorityChecker
* [IOTDB-2624] Fix "overlapped data should be consumed first" occurs when executing query
* [IOTDB-2640] Fix cross compaction recover bug
* [IOTDB-2641] Fix time range of TsFile resource overlaps after unseq compaction
* [IOTDB-2642] Fix the new file has a higher compact priority than the old file in unseq compaction
* Fix a logical bug in processPlanLocally in cluster mode
* Throw Exception while using last query with align by device
* Add a judgement to determine raft log size can fit into buffer before log appending in cluster mode
* Fix grafana can't be used bug

# Apache IoTDB 0.12.4

## New Features

* [IOTDB-1823] group by multi level

## Improvements

* [IOTDB-2027] Rollback invalid entry after WAL writing failure
* [IOTDB-2061] Add max concurrent sub query parameter, read data in batches to limit max IO and add max cached buffer size configuration
* [IOTDB-2065] release TsFileSequenceReader soon when it is no longer used
* [IOTDB-2072] Remove TVListAllocator to reduce the TVList mem cost
* [IOTDB-2101] Reduce the memory footprint of QueryDataSource
* [IOTDB-2102] Push limit operator down to each reader
* [IOTDB-2123] Accelerate recovery process
* update user guide for cpp-cpi and disable compiling nodejs in cpp-cli
* Ignore too many WAL BufferOverflow log


## Bug Fixes
* [IOTDB-1408] Statement with 'as' executes incorrectly in mutil-path scenes
* [IOTDB-2023] Fix serializing and deserializing bugs of Filters
* [IOTDB-2025] Fix count nodes and devices incorrectly in cluster
* [IOTDB-2031] Fix incorrect result of descending query with value filter in cluster
* [IOTDB-2032] Fix incorrect result of descending query with multiple time partitions
* [IOTDB-2039] Fix data redundant after too many open files exception occurs during compaction
* [IOTDB-2047] Fix NPE when memControl is disabled and insert TEXT value to a non-TEXT series
* [IOTDB-2058] Fix Query is blocked without sub-query-threads exist bug
* [IOTDB-2063] Fix MinTimeDescAggregationResult implementation bug
* [IOTDB-2064] Fix the NPE caused by map serde
* [IOTDB-2068] Fix GZIP compressor meets ArrayIndexOutOfBoundsException
* [IOTDB-2124] the filtering condition does not take efffect for last query in cluster
* [IOTDB-2138] Fix data loss after IoTDB recover
* [IOTDB-2140] Fix merge throw NullPointerException
* [IOTDB-2152] PyClient: Override `__eq__()` of TSDataType, TSEncoding and Compressor to avoid unexpected comparation behaviour
* [IOTDB-2160] Fix cluster groupby query cross-node reference leaks
* [ISSUE-3335] Fix the bug of start-cli.sh -e mode can't work with wild card \*
* fix memory leak: replace RandomDeleteCache with Caffine CacheLoader
* Fix connection refused using session when users forget to set client ip


# Apache IoTDB 0.12.3

## Improvements

* [IOTDB-842] Better Export/Import-CSV Tool
* [IOTDB-1738] Cache paths list in batched insert plan
* [IOTDB-1792] remove tomcat-embed dependency and make all transitive dependencies versions consistent
* [ISSUE-4072] Parallel insert records in Session
* Print the file path while meeting error in case of reading chunk

## Bug Fixes

* [IOTDB-1275] Fix backgroup exec for cli -e function causes an infinite loop
* [IOTDB-1287] Fix C++ class Session has 2 useless sort()
* [IOTDB-1289] fix CPP mem-leak in SessionExample.cpp insertRecords()
* [IOTDB-1484] fix auto create schema in cluster
* [IOTDB-1578] Set unsequnce when loading TsFile with the same establish time
* [IOTDB-1619] Fix an error msg when restart iotdb-cluster
* [IOTDB-1629] fix the NPE when using value fill in cluster mode
* [IOTDB-1632] Fix Value fill function fills even when the data exists
* [IOTDB-1651] add reconnect to solve out of sequence in sync module
* [IOTDB-1659] Fix Windows CLI cannot set maxPRC less than or equal to 0
* [IOTDB-1670] Fix cli -e mode didn't fetch timestamp_precision from server
* [IOTDB-1674] Fix command interpret error causing somaxconn warning failed
* [IOTDB-1677] Fix not generate file apache-iotdb-0.x.x-client-cpp-linux-x86_64-bin.zip.sha512
* [IOTDB-1678] Fix client-cpp session bug: can cause connection leak.
* [IOTDB-1679] client-cpp: Session descontruction need release server resource
* [IOTDB-1690] Fix align by device type cast error
* [IOTDB-1693] fix IoTDB restart does not truncate broken ChunkGroup bug
* [IOTDB-1703] Fix MManager slow recover with tag
* [IOTDB-1714] fix Could not find or load main class when start with jmx on win 
* [IOTDB-1723] Fix concurrency issue in compaction selection
* [IOTDB-1726] Wrong hashCode() and equals() method in ChunkMetadata
* [IOTDB-1727] Fix Slow creation of timeseries with tag
* [IOTDB-1731] Fix sync error between different os
* [IOTDB-1733] Fix dropping built-in function
* [IOTDB-1741] Avoid double close in level compaction execution
* [IOTDB-1785] Fix Illegal String ending with . being parsed to PartialPath
* [IOTDB-1836] Fix Query Exception Bug after deleting all sgs
* [IOTDB-1837] Fix tagIndex rebuild failure after upgrade mlog from mlog.txt to mlog.bin
* [IOTDB-1838] The compacting status in SGP is always false
* [IOTDB-1846] Fix the error when count the total number of devices in cluster mode
* [IoTDB-1847] Not throw excpetion when pulling non--existent time series
* [IOTDB-1850] Fix deserialize page merge rate limiter
* [IoTDB-1865] Compaction is blocking when removing old files in Cluster
* [IOTDB-1868] Use RwLock to reduce the lock time for nodeRing
* [IOTDB-1872] Fix data increases abnormally after IoTDB restarts
* [IOTDB-1877] Fix Sync recovery and reconnection bugs in both sender and receiver
* [IOTDB-1879] Fix some Unsequence files never be merged to higher level or Sequence folder
* [IOTDB-1887] Fix importing csv data containing null throws exception
* [IOTDB-1893] Fix Can not release file lock in sync verify singleton 
* [IOTDB-1895] Cache leader optimization for batch write interfaces on multiple devices
* [IOTDB-1903] Fix IndexOutOfRangeException when starting IoTDB
* [IoTDB-1913] Fix When exporting a amount of data from csv, it will report network error or OOM
* [IOTDB-1925] Fix the modification of max_select_unseq_file_num_in_each_compaction parameter does not take effect
* [IOTDB-1958] Add storage group not ready exception
* [IOTDB-1961] Cluster query memory leak
* [IOTDB-1975] OOM caused by that MaxQueryDeduplicatedPathNum doesn't take effect
* [IOTDB-1983] Fix DescReadWriteBatchData serializing bug
* [IOTDB-1990] Fix unchecked null result by calling IReaderByTimestamp.getValuesInTimestamps()
* [ISSUE-3945] Fix Fuzzy query not support multiDevices and alignByDevice Dataset
* [ISSUE-4288] Fix CI issue caused by the invalid pentaho download url
* [ISSUE-4293] SessionPool: InterruptedException is not properly handled in synchronized wait()
* [ISSUE-4308] READ_TIMESERIES privilege granted to users and roles can not take effect when quering by UDFs
* fix merge ClassCastException: MeasurementMNode
* change sync version check to major version
* init dummyIndex after restart cluster

# Apache IoTDB 0.12.2

## New Features

* [IOTDB-959] Add create storage group Grammar
* [IOTDB-1399] Add a session interface to connect multiple nodes
* [IOTDB-1466] Support device template
* [IOTDB-1491] UDTF query supported in cluster
* [IOTDB-1496] Timed flush memtable
* [IOTDB-1536] Support fuzzy query REGEXP
* [IOTDB-1561] Support fill by specific value
* [IOTDB-1565] Add sql: set system to readonly/writable
* [IOTDB-1569] Timed close TsFileProcessor
* [IOTDB-1586] Support mysql-style Like clause
* [ISSUE-3811] Provide a data type column for the last query dataset
* TTL can be set to the prefix path of storage group
* add JMX monitor to all ThreadPools in the server module

## Improvements

* [IOTDB-1566] Do not restrict concurrent write partitions
* [IOTDB-1585] ModificationFile‘s write interface blocking
* [IOTDB-1587] SessionPool optimization: a more aggressive Session creation strategy
* Use StringCachedPool in TsFileResource to reduce the memory size
* write performance optimization when replicaNum == 1
* Optimize Primitive Array Manager
* Function Improvement: add overlapped page rate in Tracing

## Bug Fixes

* [IOTDB-1282] fix C++ class SessionDataSet mem-leak
* [IOTDB-1407] fix Filtering time series based on tags query fails Occasionally
* [IOTDB-1437] Fix the TsFileSketchTool NPE
* [IOTDB-1442] Time filter & TTL do not take effect in cluster
* [IOTDB-1452] remove compaction log/ change logger to daily
* [IOTDB-1447] ClientPool is blocking other nodes when one node fails
* [IOTDB-1456] Fix Error occurred while executing delete timeseries statement
* [IOTDB-1461] Fix compaction conflicts with ttl
* [IOTDB-1462] Fix cross space compaction recover null pointer bug
* [IOTDB-1464] fix take byte array null pointer
* [IOTDB-1469] fix cross space compaction lost data bug
* [IOTDB-1471] Fix path not right in "sg may not ready" log
* [IOTDB-1475] MeasurementId check while create timeseries or template/ disable time or timestamp in timeseries path
* [IOTDB-1488] Fix metaMember's forwarding clientPool timeout in cluster module
* [IOTDB-1494] fix compaction block flush bug
* [IoTDB-1499] Remove series registration using IoTDBSink
* [IoTDB-1501] Fix compaction recover delete tsfile bug
* [IOTDB-1529] Fix mlog recover idx bug and synchronize setStorageGroup
* [IOTDB-1537] fix insertTablet permission
* [IOTDB-1539] Fix delete operation with value filter is abnormal
* [IOTDB-1540] Bug Fix: 500 when using IN operator
* [IOTDB-1541] Fix query result not right due to non-precise time index of resource
* [IOTDB-1542] Cpp client segment fault: char[] buffer overflow caused by long exception message
* [IOTDB-1545] Query dataset memory leak on server caused by cpp client
* [IOTDB-1546] Optimize the Upgrade Tool rewrite logic to reduce the temp memory cost
* [IOTDB-1552] Only allow equivalent filter for TEXT data type
* [IOTDB-1556] Abort auto create device when meet exception in setStorageGroup
* [IOTDB-1574] Deleted file handler leak
* [IOTDB-1580] Error result of order by time desc when enable time partition
* [IOTDB-1584] Doesn't support order by time desc in cluster mode
* [IOTDB-1588] Bug fix: MAX_TIME is incorrect in cluster mode
* [IOTDB-1594] Fix show timeseries returns incorrect tag value
* [IOTDB-1600] Fix InsertRowsOfOneDevicePlan being not supported in cluster mode
* [IOTDB-1610] Fix TsFileRewriteTool writing incorrect data file
* [ISSUE-3116] Bug when using natural month unit in time interval in group by query
* [ISSUE-3316] Query result with the same time range is inconsistent in group by query
* [ISSUE-3436] Fix query result not right after deleting multiple time interval of one timeseries
* [ISSUE-3458] fix load configuration does not take effect
* [ISSUE-3545] Fix Time interval value is disorder in group by month
* [ISSUE-3653] fix Max_time and last return inconsistent result
* [ISSUE-3690] Memory leaks on the server when cpp client invokes checkTimeseriesExists
* [ISSUE-3805] OOM caused by Chunk cache
* [ISSUE-3865] Meaningless connection reset issues caused by low default value for SOMAXCONN
* Fix DataMigrationExample OOM if migrate too many timeseries
* Handle false positive cases which may cause NPE of tsfile bloom filter
* Fix Windows shell error on JDK11 & fix iotdb-env.bat not working
* Fix cluster auto create schema bug when retry locally
* Fix thrift out of sequence in cluster module
* Skip non exist measurement in where clause in align by device
* fix blocking query when selecting TsFile in compaction
* Fix redundant data in compaction recover
* Fix load tsfile with time partition enable

## Incompatible changes

* [IOTDB-1485] Replace tsfile_size_threshold by unseq_tsfile_size/seq_tsfile_size

## Miscellaneous changes

* [IOTDB-1499] Remove unused exception throwing notation in IoTDBSink
* [IOTDB-1500] Remove current dynamic query memory control
* [ISSUE-3674] Disable thrift code generation for Javascript
* enable cacheLeader by default
* add audit log when execute delete and set sg for tracing
* modify nodeTool user to root

# Apache IoTDB 0.12.1

## Bug Fixes

* [GITHUB-3373] Remove the broken cached leader connection & optimize the insertRecords method in session
* [IOTDB-1433] Fix bug in getMetadataAndEndOffset when querying non-exist device
* [IOTDB-1432] fix level compaction loss data
* [IOTDB-1427] Fix compaction lock with query
* [IOTDB-1420] Fix compaction ttl bug
* [IOTDB-1419] Remove redundant clearCompactionStatus, fix continuous compaction doesn't take effect when
  enablePartition
* [IOTDB-1415] Fix OOM caused by ChunkCache
* [IOTDB-1414] NPE occurred when call getStorageGroupNodeByPath() method using not exist path
* [IOTDB-1412] Unclear exception message thrown when executing empty InsertTabletPlan
* [IOTDB-1411] Fix thriftMaxFrameSize and thriftDefaultBufferSize does not in effect
* [IOTDB-1398] Do not select unseq files when there are uncompacted old unseq files
* [IOTDB-1390] Fix unseq compaction loss data bug
* [IOTDB-1384] Fix group by bug
* [ISSUE-3378] Fix NPE when clear upgrade folder; Fix some upgraded pageHeader missing statistics
* [GITHUB-3339] Try to fix sg dead lock
* [GITHUB-3329] Fix upgrade NPE and DeadLock
* [GITHUB-3319] Fix upgrade tool cannot close file reader
* [IOTDB-1212] Fix The given error message is not right when executing select sin(non_existence) from root.sg1.d1
* [IOTDB-1219] Fix a potential NPE issue in UDF module
* [IOTDB-1286] Fix 4 C++ mem-leak points
* [IOTDB-1294] Fix delete operation become invalid after compaction
* [IOTDB-1313] Fix lossing time precision when import csv with unsupported timestamp format
* [IOTDB-1316] The importCsv tool should continue inserting if a part of insertion failed
* [IOTDB-1317] Fix log CatchUp always failed due to not check the follower's match index
* [IOTDB-1323] Fix return a success message when encounter RuntimeException during the insertion process
* [IOTDB-1325] Fix StackOverflow Exception in group by natural month query
* [IOTDB-1330] Fix the load tsfile bug when the cross multi partition's tsfile only have one page
* [IOTDB-1348] Fix Last plan not work in cluster mode
* [IOTDB-1376] Fix BatchProcessException was not correctly handled in BaseApplier
* [ISSUE-3277] Fix TotalSeriesNumber in MManager counted twice when recovering
* [ISSUE-3116] Fix bug when using natural month unit in time interval in group by query
* [ISSUE-3309] Fix InsertRecordsOfOneDevice runs too slow
* Fix the plan index is always zero when using insertRecords interface to run the cluster
* Add authority check for users create timeseries using executeBatch interface without the privilege
* Fix versionInfo NPE when query upgrading 0.11 tsfile
* Fix upgrade tool cannot load old tsfile if time partition enabled in 0.11
* Fix import csv throw ArrayOutOfIndexError when the last value in a line is null
* Fix upgrade tool cannot close file reader

## Improvements

* [GITHUB-3399] Change the default primitive array size to 32
* [IOTDB-1387] Support Without Null ALL in align by device clause, Filter RowRecord automatically if any column in it is
  null or all columns are null
* [IOTDB-1385] Extract the super user to the configuration
* [IOTDB-1315] ExportCsvTool should support timestamp `yyyy-MM-dd'T'HH:mm:ss.SSSZ`
* [IOTDB-1339] optimize TimeoutChangeableTSnappyFramedTransport
* [IOTDB-1356] Separate unseq_file_num_in_each_level from selecting candidate file in unseq compaction
* [IOTDB-1357] Compaction use append chunk merge strategy when chunk is already large enough
* [IOTDB-1380] Automatically close the dataset while there is no more data
* Optimize sync leader for meta

## New Features

* [GITHUB-3389] TTL can be set to any path
* [GITHUB-3387] Add parameter compaction_interval=10000ms
* [IOTDB-1190] Fully support HTTP URL char set in timeseries path
* [IOTDB-1321][IOTDB-1322] Filter RowRecord automatically if any column in it is null or all columns are null
* [IOTDB-1357] Compaction use append chunk merge strategy when chunk is already large
* [ISSUE-3089] Make it possible for storage groups to have name with hyphen

## Miscellaneous changes

* [GITHUB-3346] upgrade netty and claim exclusion for enforcer check
* [IOTDB-1259] upgrade libthrift from 0.12.0/0.13.0 to 0.14.1
* Uncomment the less used configurations
* Enable the configration `concurrent_writing_time_partition`


# Apache IoTDB 0.12.0

## New Features
* [IOTDB-68] New shared-nothing cluster
* [IOTDB-507] Add zeppelin-interpreter module
* [IOTDB-825] Aggregation by natural month
* [IOTDB-890] support SDT lossy compression 
* [IOTDB-944] Support UDTF (User-defined Timeseries Generating Function)
* [IOTDB-965] Add timeout parameter for query
* [IOTDB-1077] Add insertOneDeviceRecords API in java session
* [IOTDB-1055] Support data compression type GZIP
* [IOTDB-1024] Support multiple aggregated measurements for group by level statement
* [IOTDB-1276] Add explain sql support and remove debug_state parameter
* [IOTDB-1197] Add iotdb-client-go as a git submodule of IoTDB repo
* [IOTDB-1230] Support spans multi time partitions when loading one TsFile
* [IOTDB-1273] Feature/restrucutre python module as well as supporting pandas dataframe
* [IOTDB-1277] support IoTDB as Flink's data source
* [PR-2605] Add level merge to "merge" command

## Incompatible changes
* [IOTDB-1081] New TsFile Format
* [ISSUE-2730] Add the number of unseq merge times in TsFile name.


## Miscellaneous changes
* [IOTDB-868] Change mlog from txt to bin
* [IOTDB-1069] Restrict the flushing memtable number to avoid OOM when mem_control is disabled
* [IOTDB-1104] Refactor the error handling process of query exceptions
* [IOTDB-1108] Add error log to print file name while error happened
* [IOTDB-1152] Optimize regular data size in traversing
* [IOTDB-1180] Reset the system log file names and maximal disk-space size
* [ISSUE-2515] Set fetchsize through JDBC and Session
* [ISSUE-2598] Throw explicit exception when time series is unknown in where clause
* [PR-2944] Throw exception when device to be queried is not in TsFileMetaData
* [PR-2967] Log memory usage information in SystemInfo for better diagnosis

## Bug Fixes
* [IOTDB-1049] Fix NullpointerException and a delete bug in Last query
* [IOTDB-1050] Fix Count timeserise column name is wrong
* [IOTDB-1068] Fix Time series metadata cache bug
* [IOTDB-1084] Fix temporary memory of flushing may cause OOM
* [IOTDB-1106] Fix delete timeseries bug
* [IOTDB-1126] Fix the unseq tsfile delete due to merge
* [IOTDB-1135] Fix the count timeseries prefix path bug
* [IOTDB-1137] Fix MNode.getLeafCount error when existing sub-device
* [ISSUE-2484] Fix creating timeseries error by using "create" or "insert" statement
* [ISSUE-2545, 2549] Fix unseq merge end time bug
* [ISSUE-2611] An unsequence file that covers too many sequence file causes OOM query
* [ISSUE-2688] LRULinkedHashMap does not work as an LRU Cache
* [ISSUE-2709, 1178] Fix cache not cleared after unseq compaction bug, Fix windows 70,10 ci bug in unseq compaction ci
* [ISSUE-2741] getObject method in JDBC should return an Object
* [ISSUE-2746] Fix data overlapped bug after unseq compaction
* [ISSUE-2758] NullPointerException in QueryTimeManager.checkQueryAlive()
* [ISSUE-2905] Fix Files.deleteIfExists() doesn't work for HDFS file
* [ISSUE-2919] Fix C++ client memory leak bug
* [PR-2613] Fix importCSVTool import directory bug & encode bug
* [PR-2409] Fix import csv which can't import time format str
* [PR-2582] Fix sync bug for tsfiles's directory changed by vitural storage group
* [ISSUE-2911] Fix The write stream is not closed when executing the command 'tracing off'

# Apache IoTDB 0.11.4

## Bug Fixes

* IOTDB-1303 Disable group by without aggregation function in select clause
* IOTDB-1306 Fix insertion blocked caused the deadlock in memory control module
* IOTDB-1308 Fix users with READ_TIMESERIES permission cannot execute group by fill queries
* IOTDB-1344 Fix cannot create timeseries caused by the timeseries count doesn't reset when deleting storage group
* IOTDB-1384 Some value will disappear while using group by query
* IOTDB-1398 Do not select unseq files when there are uncompacted old unseq files
* ISSUE-3316 Fix query result with the same time range is inconsistent in group by query
* Fix TotalSeriesNumber in MManager counted twice when recovering
* Fix unseq compaction throws a wrong exception if some paths are not in the file
* Fix overlapped data should be consumed first exception when query

## Improvements

* IOTDB-1356 Separate unseq_file_num_in_each_level from selecting candidate file in unseq compaction
* IOTDB-1412 Unclear exception message thrown when executing empty InsertTabletPlan
* continuous compaction in level compaction strategy when no tsfile is to be closed

## New Features

* support brackets with number in timeseries path

# Apache IoTDB 0.11.3

## Bug Fixes
* ISSUE-2505 ignore PathNotExistException in recover and change recover error to warn
* IOTDB-1119 Fix C++ SessionDataSet bug when reading value buffer
* Fix SessionPool does not recycle session and can not offer new Session due to RunTimeException
* ISSUE-2588 Fix dead lock between deleting data and querying in parallel
* ISSUE-2546 Fix first chunkmetadata should be consumed first
* IOTDB-1126 Fix unseq tsfile is deleted due to compaction
* IOTDB-1137 MNode.getLeafCount error when existing sub-device
* ISSUE-2624 ISSUE-2625 Avoid OOM if user don't close Statement and Session manually
* ISSUE-2639 Fix possible NPE during end query process
* Alter IT for An error is reported and the system is suspended occasionally
* IOTDB-1149 print error for -e param when set maxPRC<=0
* IOTDB-1247 Fix the insert blocked caused the bugs in mem control module
* ISSUE-2648 Last query not right when having multiple devices
* Delete mods files after compaction
* ISSUE-2687 fix insert NaN bug
* ISSUE-2598 Throw explicit exception when time series is unknown in where clause
* Fix timeseriesMetadata cache is not cleared after the TsFile is deleted by a compaction
* ISSUE-2611 An unsequence file that covers too many sequence file causes OOM query
* IOTDB-1135 Fix count timeseries bug when the paths are nested
* ISSUE-2709 IOTDB-1178 Fix cache is not cleared after compaction
* ISSUE-2746 Fix data overlapped bug after the elimination unseq compaction process
* Fix getObject method in JDBC should return an Object
* IOTDB-1188 Fix IoTDB 0.11 unable to delete data bug
* Fix when covering a tsfile resource with HistoricalVersion = null, it’ll throw a NPE
* fix the elimination unseq compaction may loss data bug after a delete operation is executed
* Fix a bug of checking time partition in DeviceTimeIndex
* Throw exeception when device to be queried is not in tsFileMetaData
* Fix unseq compaction file selector conflicts with time partition bug
* Fix high CPU usage during the compaction process

## Improvements
* IOTDB-1140 optimize regular data encoding
* Add more log for better tracing
* Add backgroup exec for cli -e function
* Add max direct memory size parameter to env.sh
* Change last cache log to debug level

## New Features
* Add explain sql support


# Apache IoTDB 0.11.2

## Bug Fixes
* IOTDB-1049 Fix Nullpointer exception and a delete bug in Last query
* IOTDB-1060 Support full deletion for delete statement without where clause
* IOTDB-1068 Fix Time series metadata cache bug
* IOTDB-1069 restrict the flushing memtable number to avoid OOM when mem_control is disabled
* IOTDB-1077 add insertOneDeviceRecords API in java session
* IOTDB-1087 fix compaction block flush: flush do not return until compaction finished
* IOTDB-1106 Delete timeseries statement will incorrectly delete other timeseries
* Github issue-2137 fix grafana value-time position bug
* Github issue-2169 GetObject returns String for all data types
* Github issue-2240 fix Sync failed: Socket is closed by peer
* Github issue-2387 The deleteData method exists in Session but not in SessionPool.
* add thrift_max_frame_size in iotdb-engine.properties
* Fix incorrect last result after deleting all data
* Fix compaction recover block restart: IoTDB cannot restart until last compaction recover task finished
* Fix compaction ignore modification file: delete does not work after compaction
* print more insert error message in client
* expose enablePartition parameter into iotdb-engines.properpties

# Apache IoTDB 0.11.1

## Bug Fixes
* IOTDB-990 cli parameter maxPRC shouldn't to be set zero
* IOTDB-993 Fix tlog bug
* IOTDB-994 Fix can not get last_value while doing the aggregation query along with first_value
* IOTDB-1000 Fix read redundant data while select with value filter with unseq data
* IOTDB-1007 Fix session pool concurrency and leakage issue when pool.close is called
* IOTDB-1016 overlapped data should be consumed first
* IOTDB-1021 Fix NullPointerException when showing child paths of non-existent path
* IOTDB-1028 add MAX\_POINT\_NUMBER format check
* IOTDB-1034 Fix Show timeseries error in Chinese on Windows
* IOTDB-1035 Fix bug in getDeviceTimeseriesMetadata when querying non-exist device
* IOTDB-1038 Fix flink set storage group bug
* ISSUE-2179 fix insert partial tablet with binary NullPointer bug
* add reject status code
* Update compaction level list delete
* Fix query result is not correct
* Fix import errors in Session.py and SessionExample.py
* Fix modules can not be found when using pypi to pack client-py
* Fix Count timeseries group by level bug
* Fix desc batchdata count bug

# Apache IoTDB 0.11.0

## New Features

* IOTDB-627 Support range deletion for timeseries
* IOTDB-670 Add raw data query interface in Session
* IOTDB-716 add lz4 compression
* IOTDB-736 Add query performance tracing
* IOTDB-776 New memory control strategy
* IOTDB-813 Show storage group under given path prefix
* IOTDB-848 Support order by time asc/desc
* IOTDB-863 add a switch to drop ouf-of-order data
* IOTDB-873 Add count devices DDL
* IOTDB-876 Add count storage group DDL
* IOTDB-926 Support reconnection of Session
* IOTDB-941 Support 'delete storage group <prefixPath>'
* IOTDB-968 Support time predicate in select last, e.g., select last * from root where time >= T
* Show alias if it is used in query
* Add level compaction strategy
* Add partialInsert

## Incompatible changes

* IOTDB-778 Support double/single quotation in Path
* IOTDB-870 change tags and attributes output to two columns with json values

## Miscellaneous changes

* IOTDB-784 Update rpc protocol to V3
* IOTDB-790 change base_dir to system_dir
* IOTDB-829 Accelerate delete multiple timeseries
* IOTDB-839 Make Tablet api more friendly
* IOTDB-902 Optimize max_time aggregation
* IOTDB-916 Add a config entry to make Last cache configurable
* IOTDB-928 Make ENCODING optional in create time series sentence
* IOTDB-938 Re-implement Gorilla encoding algorithm
* IOTDB-942 Optimization of query with long time unsequence page
* IOTDB-943 Fix cpu usage too high
* Add query load log
* Add merge rate limiting

## Bug Fixes

* IOTDB-749 Avoid select * from root OOM
* IOTDB-774 Fix "show timeseries" OOM problem
* IOTDB-832 Fix sessionPool logic when reconnection failed
* IOTDB-833 Fix JMX cannot connect IoTDB in docker
* IOTDB-835 Delete timeseries and change data type then write failed
* IOTDB-836 Statistics classes mismatched when endFile （delete timeseries then recreate）
* IOTDB-837 ArrayIndexOutOfBoundsException if the measurementId size is not consistent with the value size
* IOTDB-847 Fix bug that 'List user privileges' cannot apply to 'root'
* IOTDB-850 a user could list others privilege bug
* IOTDB-851 Enhance failure tolerance when recover WAL (enable partial insertion)
* IOTDB-855 Can not release Session in SessionPool if RuntimeException occurs
* IOTDB-868 Can not redo mlogs with special characters like comma
* IOTDB-872 Enable setting timezone at client
* IOTDB-877 fix prefix bug on show storage group and show devices
* IOTDB-904 fix update last cache NullPointerException
* IOTDB-920 Disable insert row that only contains time/timestamp column
* IOTDB-921 When execute two query simultaneously in one statement, got error
* IOTDB-922 Int and Long can convert to each other in ResultSet
* IOTDB-947 Fix error when counting node with wildcard
* IOTDB-949 Align by device doesn't support 'T*' in path.
* IOTDB-956 Filter will be missed in group by time align by device
* IOTDB-963 Redo deleteStorageGroupPlan failed when recovering
* IOTDB-967 Fix xxx does not have the child node xxx Bug in count timeseries
* IOTDB-970 Restrict log file number and size
* IOTDB-971 More precise error messages of slimit and soffset 
* IOTDB-975 when series does not exist in TsFile, reading wrong ChunkMetadataList

# Apache IoTDB (incubating) 0.10.1

* [IOTDB-797] InsertTablet deserialization from WAL error
* [IOTDB-788] Can not upgrade all storage groups
* [IOTDB-792] deadlock when insert while show latest timeseries
* [IOTDB-794] Rename file or delete file Error in start check in Windows
* [IOTDB-795] BufferUnderflowException in Hive-connector
* [IOTDB-766] Do not release unclosed file reader, a small memory leak
* [IOTDB-796] Concurrent Query throughput is low
* Query result is not correct when some unsequence data exists
* Change the default fetch size to 10000 in session
* [IOTDB-798] fix a set rowLimit and rowOffset bug
* [IOTDB-800] Add a new config type for those parameters which could not be modified any more after the first start 
* [IOTDB-802] Improve "group by" query performance
* [IOTDB-799] remove log visualizer tool from v0.10 
* fix license-binary  
* [IOTDB-805] Fix BufferUnderflowException when querying TsFile stored in HDFS 
* python session client ver-0.10.0
* [IOTDB-808] fix bug in selfCheck() truncate 
* fix doc of MeasurementSchema in Tablet 
* [IOTDB-811] fix upgrading mlog many times when upgrading system.properties crashed
* Improve IoTDB restart process
* remove jol-core dependency which is introduced by hive-serde 2.8.4
* remove org.json dependency because of license compatibility
* [ISSUE-1551] fix set historical version when loading additional tsfile


# Apache IoTDB (incubating) 0.10.0

## New Features

* IOTDB-217 A new GROUPBY syntax, e.g., select avg(s1) from root.sg.d1.s1 GROUP BY ([1, 50), 5ms)
* IOTDB-220 Add hot-load configuration function
* IOTDB-275 allow using user defined JAVA_HOME and allow blank space in the JAVA_HOME
* IOTDB-287 Allow domain in JDBC URL
* IOTDB-292 Add load external tsfile feature
* IOTDB-297 Support "show flush task info"
* IOTDB-298 Support new Last point query. e.g, select last * from root
* IOTDB-305 Add value filter function while executing align by device
* IOTDB-309 add Dockerfiles for 0.8.1, 0.9.0, and 0.9.1
* IOTDB-313 Add RandomOnDiskUsableSpaceStrategy
* IOTDB-323 Support insertRecords in session
* IOTDB-337 Add timestamp precision properties for grafana
* IOTDB-343 Add test method in session
* IOTDB-396 Support new query clause: disable align, e.g., select * from root disable align
* IOTDB-447 Support querying non-existing measurement and constant measurement
* IOTDB-448 Add IN operation, e.g., where time in (1,2,3)
* IOTDB-456 Support GroupByFill Query, e.g., select last_value(s1) from root.sg.d1 GROUP BY ([1, 10), 2ms) FILL(int32[previousUntilLast])
* IOTDB-467 The CLI displays query results in a batch manner
* IOTDB-497 Support Apache Flink Connector with IoTDB
* IOTDB-558 add text support for grafana
* IOTDB-560 Support Apache Flink connecter with TsFile
* IOTDB-565 MQTT Protocol Support, disabled by default, open in iotdb-engine.properties
* IOTDB-574 Specify configuration when start iotdb
* IOTDB-588 Add tags and attributes management
* IOTDB-607 add batch create timeseries in native interface
* IOTDB-612 add limit&offset to show timeseries
* IOTDB-615 Use TsDataType + Binary to replace String in insert plan
* IOTDB-617 Support alter one time series's tag/attribute
* IOTDB-630 Add a jdbc-like way to fetch data in session
* IOTDB-640 Enable system admin sql (flush/merge) in JDBC or Other API
* IOTDB-671 Add clear cache command
* Support open and close time range in group by, e.g, [), (]
* Online upgrade from 0.9.x
* Support special characters in path: -/+&%$#@
* IOTDB-446 Support path start with a digit, e.g., root.sg.12a
* enable rpc compression in session pool
* Make JDBC OSGi usable and added a feature file
* add printing one resource file tool
* Allow count timeseries group by level=x using default path
* IOTDB-700 Add OpenID Connect based JWT Access as alternative to Username / Password
* IOTDB-701 Set heap size by percentage of system total memory when starts
* IOTDB-708 add config for inferring data type from string value
* IOTDB-715 Support previous time range in previousuntillast
* IOTDB-719 add avg_series_point_number_threshold in config
* IOTDB-731 Continue write inside InsertPlan 
* IOTDB-734 Add Support for NaN in Double / Floats in SQL Syntax.
* IOTDB-744 Support upsert alias 


## Incompatible changes

* IOTDB-138 Move All metadata query to usual query
* IOTDB-322 upgrade to thrift 0.12.0-0.13.0
* IOTDB-325 Refactor Statistics in TsFile
* IOTDB-419 Refactor the 'last' and 'first' aggregators to 'last_value' and 'first_value'
* IOTDB-506 upgrade the rpc protocol to v2 to reject clients or servers that version < 0.10
* IOTDB-587 TsFile is upgraded to version 2
* IOTDB-593 add metaOffset in TsFileMetadata
* IOTDB-597 Rename methods in Session: insertBatch to insertTablet, insertInBatch to insertRecords, insert to insertRecord
* RPC is incompatible, you can not use client-v0.9 to connect with server-v0.10
* TsFile format is incompatible, will be upgraded when starting 0.10
* Refine exception code in native api

## Miscellaneous changes

* IOTDB-190 upgrade from antlr3 to antlr4
* IOTDB-418 new query engine
* IOTDB-429 return empty dataset instead of throw exception, e.g., show child paths root.*
* IOTDB-445 Unify the keyword of "timestamp" and "time"
* IOTDB-450 Add design documents
* IOTDB-498 Support date format "2020-02-10"
* IOTDB-503 Add checkTimeseriesExists in java native api
* IOTDB-605 Add more levels of index in TsFileMetadata for handling too many series in one device
* IOTDB-625 Change default level number: root is level 0
* IOTDB-628 rename client to cli
* IOTDB-621 Add Check isNull in Field for querying using session
* IOTDB-632 Performance improve for PreviousFill/LinearFill
* IOTDB-695 Accelerate the count timeseries query 
* IOTDB-707 Optimize TsFileResource memory usage  
* IOTDB-730 continue write in MQTT when some events are failed
* IOTDB-729 shutdown uncessary threadpool 
* IOTDB-733 Enable setting for mqtt max length 
* IOTDB-732 Upgrade fastjson version to 1.2.70
* Allow "count timeseries" without a prefix path
* Add max backup log file number
* add rpc compression api in client and session module
* Continue writing the last unclosed file
* Move the vulnera-checks section into the apache-release profile to accelerate compile
* Add metaquery in python example
* Set inferType of MQTT InsertPlan to true



## Bug Fixes

* IOTDB-125 Potential Concurrency bug while deleting and inserting happen together
* IOTDB-185 fix start-client failed on WinOS if there is blank space in the file path; let start-server.bat suport jdk12,13 etc
* IOTDB-304 Fix bug of incomplete HDFS URI
* IOTDB-341 Fix data type bug in grafana
* IOTDB-346 Fix a bug of renaming tsfile in loading function
* IOTDB-370 fix a concurrent problem in parsing sql
* IOTDB-376 fix metric to show executeQuery
* IOTDB-392 fix export CSV
* IOTDB-393 Fix unclear error message for no privilege users
* IOTDB-401 Correct the calculation of a chunk if there is no data in the chunk, do not flush empty chunk
* IOTDB-412 Paths are not correctly deduplicated
* IOTDB-420 Avoid encoding task dying silently
* IOTDB-425 fix can't change the root password.
* IOTDB-459 Fix calmem tool bug
* IOTDB-470fix IllegalArgumentException when there exists 0 byte TsFile
* IOTDB-529 Relative times and NOW() operator cannot be used in Group By
* IOTDB-531 fix issue when grafana visualize boolean data
* IOTDB-546 Fix show child paths statement doesn't show quotation marks
* IOTDB-643 Concurrent queries cause BufferUnderflowException when storage in HDFS
* IOTDB-663 Fix query cache OOM while executing query
* IOTDB-664 Win -e option
* IOTDB-669 fix getting two columns bug while ”show devices“ in session
* IOTDB-692 merge behaves incorrectly
* IOTDB-712 Meet BufferUnderflowException and can not recover
* IOTDB-718 Fix wrong time precision of NOW()
* IOTDB-735 Fix Concurrent error for MNode when creating time series automatically 
* IOTDB-738 Fix measurements has blank 

* fix concurrent auto create schema conflict bug
* fix meet incompatible file error in restart
* Fix bugs of set core-site.xml and hdfs-site.xml paths in HDFS storage
* fix execute flush command while inserting bug
* Fix sync schema pos bug
* Fix batch execution bug, the following sqls will all fail after one error sql
* Fix recover endTime set bug


# Apache IoTDB (incubating) 0.9.3

## Bug Fixes
- IOTDB-531 Fix that JDBC URL does not support domain issue
- IOTDB-563 Fix pentaho cannot be downloaded because of spring.io address
- IOTDB-608 Skip error Mlog
- IOTDB-634 Fix merge caused errors for TsFile storage in HDFS
- IOTDB-636 Fix Grafana connector does not use correct time unit

## Miscellaneous changes
- IOTDB-528 Modify grafana group by
- IOTDB-635 Add workaround when doing Aggregation over boolean Series
- Remove docs of Load External Tsfile
- Add Grafana IoTDB Bridge Artifact to distribution in tools/grafana folder


# Apache IoTDB (incubating) 0.9.2

## Bug Fixes
- IOTDB-553 Fix Return Empty ResultSet when queried series doesn't exist
- IOTDB-575 add default jmx user and password; fix issues that jmx can't be accessed remotely
- IOTDB-584 Fix InitializerError when recovering files on HDFS
- Fix batch insert once an illegal sql occurs all the sqls after that will not succeed
- Fix concurrent modification exception when iterator TsFileResourceList 
- Fix some HDFS config issues 
- Fix runtime exception not be catched and sync schema pos was nullpointer bug in DataTransferManager
- Fix python rpc grammar mistakes
- Fix upgrade ConcurrentModificationException

## Miscellaneous changes
- IOTDB-332 support Chinese characters in path
- IOTDB-316 add AVG function to 4-SQL Reference.md and modify style 
- improve start-server.bat by using quotes to protect against empty entries
- Add Chinese documents for chapter 4.2
- change download-maven-plugin to 1.3.0
- add session pool 
- add insertInBatch in Session
- add insertInBatch to SessionPool
- modify 0.9 docs to fit website
- remove tsfile-format.properties
- add bloom filter in iotdb-engien.properties
- update server download doc
- typos fix in Rel/0.9 docs
- support 0.12.0 and 0.13.0 thrift

# Apache IoTDB (incubating) 0.9.1

## Bug Fixes

- IOTDB-159 Fix NullPointerException in SeqTsFileRecoverTest and UnseqTsFileRecoverTest
- IOTDB-317 Fix a bug that "flush + wrong aggregation query" causes the following queries to fail
- IOTDB-324 Fix inaccurate statistics when writing in batch
- IOTDB-327 Fix a groupBy-without-value-filter query bug caused by the wrong page skipping logic
- IOTDB-331 Fix a groupBy query bug when axisOrigin-startTimeOfWindow is an integral multiple of interval
- IOTDB-357 Fix NullPointerException in ActiveTimeSeriesCounter
- IOTDB-359 Fix a wrong-data-type bug in TsFileSketchTool
- IOTDB-360 Fix bug of a deadlock in CompressionRatio
- IOTDB-363 Fix link errors in Development-Contributing.md and add Development-Document.md
- IOTDB-392 Fix a bug in CSV export tool
- Fix apache rat header format error in some files

## Miscellaneous changes

- IOTDB-321 Add definitions of time expression and LEVEL in related documents
- Support pypi distribution for Python client

# Apache IoTDB (incubating) 0.9.0

## New Features

* IOTDB-143 Compaction of data file
* IOTDB-151 Support number format in timeseries path
* IOTDB-158 Add metrics web service
* IOTDB-173 Add batch write interface in session
* IoTDB-174 Add interfaces for querying device or timeseries number
* IOTDB-187 Enable to choose storage in local file system or HDFS
* IOTDB-188 Delete storage group
* IOTDB-193 Create schema automatically when inserting
* IOTDB-198 Add sync module (Sync TsFiles between IoTDB instances)
* IOTDB-199 Add a log visualization tool 
* IOTDB-203 Add "group by device" function for narrow table display
* IOTDB-205 Support storage-group-level Time To Live (TTL)
* IOTDB-208 Add Bloom filter in TsFile
* IOTDB-223 Add a TsFile sketch tool
* IoTDB-226 Hive-TsFile connector
* IOTDB-239 Add interface for showing devices
* IOTDB-241 Add query and non query interface in session
* IOTDB-249 Enable lowercase in create_timeseries sql
* IOTDB-253 Support time expression 
* IOTDB-259 Level query of path
* IOTDB-282 Add "show version"
* IOTDB-294 Online upgrade from 0.8.0 to 0.9.0
* Spark-iotdb-connector
* Support quoted measurement name
* Generate cpp, go, and python thrift files under service-rpc
* Display cache hit rate through jconsole
* Support inserting data that time < 0
* Add interface (Delete timeseries) in session 
* Add a tool to print tsfileResources (each device's start and end time)
* Support watermark feature
* Add micro and nano timestamp precision

## Incompatible changes

* RPC is incompatible, you can not use client-0.8.0 to connect with server-0.9.0 or use client-0.9.0 to connect with server-0.8.0.
* Server is backward compatible, server-0.9.0 could run on data folder of 0.8.0. The data file will be upgraded background.
* Change map key in TsDigest from String to enum data type

## Miscellaneous changes

* IOTDB-144 Meta data cache for query
* IOTDB-153 Further limit fetchSize to speed up LIMIT&OFFSET query
* IOTDB-160 External sort
* IOTDB-161 Add ErrorCode of different response errors
* IOTDB-180 Get rid of JSON format in "show timeseries"
* IOTDB-192 Improvement for LRUCache
* IOTDB-210 One else if branch will never be reached in the method optimize of ExpressionOptimizer
* IOTDB-215 Update TsFile sketch tool and TsFile docs for v0.9.0
* IOTDB-221 Add a python client example
* IOTDB-233 keep metadata plan clear
* IOTDB-251 Improve TSQueryDataSet structure in RPC
* IOTDB-257 Makes the client stop fetch when dataSize equals maxPrintRowCount and change client fetchSize less than maxPrintRowCount
* IOTDB-258 Add documents for Query History Visualization Tool and Shared Storage Architecture
* IOTDB-265 Re-adjust the threshold size of memtable
* IOTDB-267 Reduce IO operations in deserializing chunk header
* IOTDB-273 Parallel recovery
* IOTDB-276 Fix inconsistent ways of judging whether a Field is null
* IOTDB-285 Duplicate fields in EngineDataSetWithoutValueFilter.java
* IOTDB-287 Restrict users to only use domain names and IP addresses.
* IOTDB-293 Variable naming convention
* IOTDB-295 Refactor db.exception
* Reconstruct Antlr3 grammar to improve performance
* Tooling for release
* Modified Decoder and SequenceReader to support old version of TsFile 
* Remove jdk constrain of jdk8 and 11
* Modify print function in AbstractClient
* Avoid second execution of parseSQLToPhysicalPlan in executeStatement

## Known Issues

* IOTDB-20 Need to support UPDATE

## Bug Fixes

* IOTDB-168&169 Fix a bug in export-csv tool and fix compatibility of timestamp formats in exportCsv, client display and sql
* IOTDB-174 Fix querying timeseries interface cannot make a query by the specified path prefix
* IOTDB-195 Using String.getBytes(utf-9).length to replace string.length() in ChunkGroupMetadata for supporting Chinese
* IOTDB-211 Use "%IOTDB_HOME%\lib\*" to refers to all .jar files in the directory in start-server.bat
* IOTDB-240 Fix unknown time series in where clause
* IOTDB-244 Fix bug when querying with duplicated columns
* IOTDB-252 Add/fix shell and bat for TsFileSketchTool/TsFileResourcePrinter
* IOTDB-266 NullPoint exception when reading not existed devices using ReadOnlyTsFile
* IOTDB-264 Restart failure due to WAL replay error
* IOTDB-290 Bug about threadlocal field in TSServiceImpl.java
* IOTDB-291 Statement close operation may cause the whole connection's resource to be released
* IOTDB-296 Fix error when skip page data in sequence reader
* IOTDB-301 Bug Fix: executing "count nodes root" in client gets "Msg:3"
* Fix Dynamic Config when Creating Existing SG or Time-series
* Fix start-walchecker scripts for letting user define the wal folder
* Fix start script to set JAVA_HOME

# Apache IoTDB (incubating) 0.8.2

 This is a bug-fix version of 0.8.1 

-  IOTDB-264 lack checking datatype before writing WAL 
-  IOTDB-317 Fix "flush + wrong aggregation" causes failed query in v0.8.x 
-  NOTICE and LICENSE file update 

# Apache IoTDB (incubating) 0.8.1

This is a bug-fix version of 0.8.0

* IOTDB-172 Bug in updating startTime and endTime in TsFileResource
* IOTDB-195 Bug about 'serializedSize' in ChunkGroupMetaData.java (for Chinese string)
* IOTDB-202 fix tsfile example data type
* IOTDB-242 fix mvn integration-test failed because the files in the target folder changes
* Abnormal publishing of sequence and unsequence data folders in DirectoryManager
* Fix a bug in TimeRange's intersects function


# Apache IoTDB (incubating) 0.8.0

This is the first official release of Apache IoTDB after joining the Incubator.

## New Features

* IOTDB-1 Add Aggregation query
* IOTDB-4 Asynchronously force sync WAL periodically
* IOTDB-5 Support data deletion
* IOTDB-11 Support start script for jdk 11 on Windows OS
* IOTDB-18 Improve startup script compatible for jdk11
* IOTDB-36 [TsFile] Enable recover data from a incomplete TsFile and continue to write
* IOTDB-37 Add WAL check tool script
* IOTDB-51 Update post-back module to synchronization module
* IOTDB-59 Support GroupBy query
* IOTDB-60 Support Fill function when query
* IOTDB-73 Add REGULAR encoding method for data with fixed frequency
* IOTDB-80 Support custom export file name
* IOTDB-81 Update travis for supporting JDK11 on Windows
* IOTDB-83 Add process bar for import script and show how many rows have been exported
* IOTDB-91 Improve tsfile-spark-connector to support spark-2.4.3
* IOTDB-93 IoTDB Calcite integration
* IOTDB-109 Support appending data at the end of a completed TsFile
* IOTDB-122 Add prepared statement in JDBC
* IOTDB-123 Add documents in Chinese
* IOTDB-130 Dynamic parameters adapter
* IOTDB-134 Add default parameter for client starting script
* Add read-only mode of IoTDB
* New storage engine with asynchronously flush and close data file
* Adding english documents
* Supporting travis + window + jdk8
* Add skipping all UTs: maven integration-test -DskipUTS=true
* Enable users define the location of their thrift compiler
* Add example module
* Add a log appender: put info, warn, error log into one file and disable log_info by default
* Recover when resource file does not exist while tsfile is complete

## Incompatible changes

If you use the previous unofficial version 0.7.0. It is incompatible with 0.8.0.

## Miscellaneous changes

* IOTDB-21 Add ChunkGroup offset information in ChunkGroupMetaData
* IOTDB-25 Add some introduction for JMX MBean Monitor in user guide
* IOTDB-29 Multiple Exceptions when reading empty measurements from TsFileSequenceReader
* IOTDB-39 Add auto repair functionality for RestorableTsFileIOWriter
* IOTDB-45 Update the license in IoTDB
* IOTDB-56 Faster getSortedTimeValuePairList() of Memtable
* IOTDB-62 Change log level from error to debug in SQL parser
* IoTDB-63 Use TsFileInput instead of FileChannel as the input parameter of some functions
* IOTDB-76 Reformat MManager.getMetadataInString() in JSON format
* IOTDB-78 Make unsequence file format more similar with TsFile
* IOTDB-95 Keep stack trace when logging or throwing an exception
* IOTDB-117 Add sync documents
* Modify ASF header for each file and add related maven plugin
* Add IoTDB env script test
* Add sync function for jdbc server to close
* Add cache directories for download jars and sonar plugin of maven in travis
* Add partition start and end offset constraints when loading ChunkGroupMetaData
* Check when creating Storage group
* Try to release memory asap in ReadOnlyMemChunk
* Add more physical plan serializer
* Move all generated tsfiles for test into the target folder
* Make TsFileWriter as AutoClosable
* Print apache-rat violation result on console
* Update multi dir avoid disk is full
* Simplify Path construction
* Separate documents into different chapter folders
* Suppress mvn log in travis
* Add mvn -B in travis

## Known Issues

* IOTDB-20 Need to support UPDATE
* IOTDB-124 Lost timeseries info after restart IoTDB
* IOTDB-125 [potential] a concurrency conflict may occur when a delete command and insertion command appears concurrently
* IOTDB-126 IoTDB will not be closed immediately after run 'stop-server.sh' script
* IOTDB-127 Chinese version documents problems

## Bug Fixes

* IOTDB-2 Maven Test failed before run mvn package -Dmaven.test.skip=true
* IOTDB-7 OpenFileNumUtilTest failed
* IOTDB-15 Fail to install IoTDB on Ubuntu 14.04
* IOTDB-16 Invalid link on https://iotdb.apache.org/#/Documents/Quick Start
* IOTDB-17 Need to update chapter Start of https://iotdb.apache.org/#/Documents/Quick Start
* IOTDB-18 IoTDB startup script does not work on openjdk11
* IOTDB-19 Fail to start start-server.sh script on Ubuntu 14.04/Ubuntu 16.04
* IOTDB-22 BUG in TsFileSequenceReader when reading tsfile
* IOTDB-24 DELETION error after restart a server
* IOTDB-26 Return error when quit client
* IOTDB-27 Delete error message
* IOTDB-30 Flush timeseries cause select to returns "Msg:null"
* IOTDB-31 Cannot set float number precision
* IOTDB-34 Invalid message for show storage group
* IOTDB-44 Error message in server log when select timeseries
* IOTDB-49 Authorizer module outputs too many debug log info
* IOTDB-50 DataSetWithoutTimeGenerator's initHeap behaves wrongly
* IOTDB-52 Cli doesn't support aggregate
* IOTDB-54 Predicates doesn't take effect
* IOTDB-67 ValueDecoder reading new page bug
* IOTDB-70 Disconnect from server when logging in fails
* IOTDB-71 Improve readPositionInfo
* IOTDB-74 THe damaged log will be skipped if it is the only log
* IOTDB-79 Long term test failed because of the version control of deletion function
* IOTDB-81 Fix Windows OS environment for Travis-CI
* IOTDB-82 File not closed in PageHeaderTest and cause UT on Windows fails
* IOTDB-84 Out-of-memory bug
* IOTDB-94 IoTDB failed to start client since the required jars are not in the right folder
* IOTDB-96 The JDBC interface throws an exception when executing the SQL statement "list user"
* IOTDB-99 List privileges User <username> on <path> cannot be used properly
* IOTDB-100 Return error message while executing sum aggregation query
* IOTDB-103 Does not give a hint when encountering unsupported data types
* IOTDB-104 MManager is incorrectly recovered when system reboots
* IOTDB-108 Mistakes in documents
* IOTDB-110 Cli inserts data normally even if there is no space left on the disk
* IOTDB-118 When the disk space is full, the storage group is created successfully
* IOTDB-121 A bug of query on value columns
* IOTDB-128 Probably a bug in iotdb official website
* IOTDB-129 A bug in restoring incomplete tsfile when system restart
* IOTDB-131 IoTDB-Grafana-Connector module error when getting the timeseries list from Grafana
* IOTDB-133 Some content is mistaken for links
* System memory check failure in iotdb-env.sh
* Time zone bug in different region
* DateTimeUtilsTest UT bug
* Problem discovered by Sonar
* Openjdk11 + linux11 does not work on travis
* Start JDBC service too slowly
* JDBC cannot be closed
* Close bug in sync thread
* Bug in MManager to get all file names of a path
* Version files of different storage groups are placed into the same place
* Import/export csv script bug
* Log level and stack print in test
* Bug in TsFile-Spark-Connector
* A doc bug of QuickStart.md
