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# 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 0.11.3

## 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 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