/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.sparql.algebra.optimize;

import org.apache.jena.atlas.lib.StrUtils ;
import org.apache.jena.sparql.algebra.Op ;
import org.apache.jena.sparql.algebra.Transform ;
import org.apache.jena.sparql.algebra.TransformCopy ;
import org.apache.jena.sparql.algebra.op.OpTable;
import org.junit.Test;
import static org.apache.jena.sparql.algebra.optimize.TransformTests.*;

/** Tests of transforms related to filters */
public class TestTransformFilters
{
    private Transform t_inequality  = new TransformFilterInequality();
    private Transform t_disjunction = new TransformFilterDisjunction();
    private Transform t_expandOneOf = new TransformExpandOneOf();
    private Transform t_implicitJoin = new TransformFilterImplicitJoin();
    private Transform t_implicitLeftJoin = new TransformImplicitLeftJoin();

    @Test public void nested_01() {
        testOp(
               "(filter (?A) (filter (?B) (table unit)))",
               new TransformCopy(),
               (String[])null);
    }


    @Test public void nested_02() {
        Transform tableChanger = new TransformCopy() {
            @Override
            public Op transform(OpTable opTable) {
                // Always a new object
                return OpTable.create(opTable.getTable());
            }
        };

        testOp(
               "(filter (?A) (filter (?B) (table unit)))",
               tableChanger,
               "(filter (exprlist ?B ?A) (table unit))");
    }


//    // JENA-1184 workaround - this optimization is current not active.
//    @Test public void equality04() {
//        // Eliminate unused
//        testOp("(filter (= ?UNUSED <x>) (bgp ( ?s ?p ?x)) )",
//               t_equality,
//               "(table empty)");
//    }

    @Test public void optionalEqualitySubQuery_01() {
        // Presence of ?test in the projection blocks the rewrite.
        // (this is actually over cautious).
        String qs = StrUtils.strjoinNL
            ( "SELECT *"
              , "WHERE {"
              , "    ?test ?p1 ?X."
              , "    FILTER ( ?test = <http://localhost/t1> )"
              , "    { SELECT ?s1 ?test { ?test ?p2 ?o2 } }"
              , "}");

        String ops = StrUtils.strjoinNL
            ("(sequence"
             ,"   (assign ((?test <http://localhost/t1>))"
             ,"     (bgp (triple <http://localhost/t1> ?p1 ?X)))"
             ,"   (project (?s1 ?test)"
             ,"     (bgp (triple ?test ?/p2 ?/o2))))"
                );
        check(qs, ops);
    }

    @Test public void optionalEqualitySubQuery_02() {
        String qs = StrUtils.strjoinNL
            ( "SELECT *"
              , "WHERE {"
              , "    ?test ?p1 ?X."
              , "    FILTER ( ?test = <http://localhost/t1> )"
              , "    { SELECT ?s1 { ?test ?p2 ?o2 } }"
              , "}");
        // JENA-616
        // Answer if FILTER equality done only after filter placement.
        String ops = StrUtils.strjoinNL
            ( "(sequence"
              , "  (assign ((?test <http://localhost/t1>))"
              , "     (bgp (triple <http://localhost/t1> ?p1 ?X)))"
              , "  (project (?s1)"
              , "     (bgp (triple ?/test ?/p2 ?/o2))) )"
                );
        // Answer if weaker filter placement done, leaving the filter on the whole sequence.
        //        String ops = StrUtils.strjoinNL
        //            ( "(assign ((?test <http://localhost/t1>))"
        //            , "  (sequence"
        //            , "    (bgp (triple <http://localhost/t1> ?p1 ?X))"
        //            , "    (project (?s1)"
        //            , "      (bgp (triple ?/test ?/p2 ?/o2)) )))"
        //            );

        check(qs, ops);
    }

    // JENA-383, simplified.
    @Test public void optionalEquality_01() {
        // Not optimized because the TransformFilterEquality does not notice
        // ?x is fixed in the expression by the join.
        String qs = StrUtils.strjoinNL
            ( "PREFIX : <http://example/> SELECT * {"
              , "    OPTIONAL { ?x :q ?o }"
              , "    FILTER(?x = :x)"
              , "    ?x :p ?o2"
              , "}"
                );
        // Answer if weaker filter placement done, leaving the filter on the whole sequence. JENA-671
        //        String ops = StrUtils.strjoinNL
        //            ( "(filter (= ?x <http://example/x>)"
        //            , "  (sequence"
        //            , "     (conditional"
        //            , "        (table unit)"
        //            , "        (bgp (triple ?x <http://example/q> ?o)))"
        //            , "     (bgp (triple ?x <http://example/p> ?o2))"
        //            , " ))"
        //            );
        //JENA-671
        String ops = StrUtils.strjoinNL
            ("(sequence"
             , "   (conditional"
             , "      (table unit)"
             , "      (bgp (triple ?x <http://example/q> ?o)))"
             , "    (assign ((?x <http://example/x>))"
             , "      (bgp (triple <http://example/x> <http://example/p> ?o2)))"
             , ")"
                );

        check(qs, ops);
    }

    @Test public void optionalEqualityScope_01() {
        String qs = StrUtils.strjoinNL
            ( "PREFIX : <http://example/> SELECT * {"
              , "    OPTIONAL { ?x :q ?o }"
              , "    FILTER(?x = :x)"
              , "    ?x :p ?o2"
              , "}"
                );
        // Transformation if filter place not happening.
        // Weaker placement.
        String ops = StrUtils.strjoinNL
            ("(assign ((?x <http://example/x>))"
             , "   (sequence"
             , "       (conditional"
             , "         (table unit)"
             , "         (bgp (triple <http://example/x> <http://example/q> ?o)))"
             , "       (bgp (triple <http://example/x> <http://example/p> ?o2))))"
                );
        //JENA-671
        // Note that "assign" is a filter as well
        // so it filters the ?x from the RHS of the conditional.
        String ops2 = StrUtils.strjoinNL
            ("(sequence"
             ,"  (conditional"
             ,"    (table unit)"
             ,"    (bgp (triple ?x <http://example/q> ?o)) )"
             ,"  (assign ((?x <http://example/x>))"
             ,"    (bgp (triple <http://example/x> <http://example/p> ?o2)))"
             ,"  )"
                );
        check(qs, ops2);
    }

    // JENA-294 part II
    @Test public void optionalEqualityScope_02() {
        // Safe to transform:  ?x is fixed.
        String qs = StrUtils.strjoinNL
            ( "PREFIX : <http://example/> SELECT * {"
              , "    ?x :p ?o2"
              , "    OPTIONAL { ?x :q ?o }"
              , "    FILTER(?x = :x)"
              , "}"
                );
        // JENA-616
        // Answer if FILTER equality optimization done only after FILTER placement.
        String ops = StrUtils.strjoinNL
            ( "(conditional"
              , "  (assign ((?x <http://example/x>))"
              , "     (bgp (triple <http://example/x> <http://example/p> ?o2)))"
              , "  (bgp (triple ?x <http://example/q> ?o))"
              , "  )"
                );
        // Answer if FILTER equality optimization done before FILTER placement
        // (and possible afterwards as well).
        //        String ops = StrUtils.strjoinNL
        //            ( "(assign ((?x <http://example/x>))"
        //            , "  (conditional"
        //            , "    (bgp (triple <http://example/x> <http://example/p> ?o2))"
        //            , "    (bgp (triple <http://example/x> <http://example/q> ?o))"
        //            , "  ))"
        //            );
        check(qs, ops);
    }

    // JENA-294 part II
    @Test public void optionalEqualityScope_03() {
        String qs = StrUtils.strjoinNL
            ( "PREFIX : <http://example/> SELECT * {"
              , "    ?z :p ?o2"
              , "    OPTIONAL { ?x :q ?o }"
              , "    FILTER(?x = :x)"
              , "}"
                );
        // Unsafe to transform:  ?x is optional.
        String ops = StrUtils.strjoinNL
            ( "(filter (= ?x <http://example/x>)"
              , "   (conditional"
              , "     (bgp (triple ?z <http://example/p> ?o2))"
              , "     (bgp (triple ?x <http://example/q> ?o))"
              , "))"
                );
        check(qs, ops);
    }

    // Scope of variable (optional, defined) cases
    @Test public void test_OptEqualityScope_04() {
        String qs = StrUtils.strjoinNL
            ( "PREFIX : <http://example/> SELECT * {"
              , "    OPTIONAL { ?x :q ?o }"
              , "    FILTER(?x = :x)"
              , "}"
                );
        // Unsafe to transform:  This may not defined ?x, then FILTER -> unbound -> error -> false
        String ops1 = StrUtils.strjoinNL
            ("(filter (= ?x <http://example/x>)"
             ,"    (conditional"
             ,"      (table unit)"
             ,"      (assign ((?x <http://example/x>))"
             ,"        (bgp (triple <http://example/x> <http://example/q> ?o)))))"
                );

        check(qs, ops1);
    }


    @Test public void disjunction01() {
        testOp("(filter (|| (= ?x <x>) (= ?x <y>)) (bgp ( ?s ?p ?x)) )",
               t_disjunction,
               "(disjunction ",
               "(assign ((?x <x>)) (bgp ( ?s ?p <x>)))",
               "(assign ((?x <y>)) (bgp ( ?s ?p <y>)))",
            ")");
    }

    @Test public void disjunction02() {
        testOp("(filter (|| (= ?x <x>) (!= ?x <y>)) (bgp ( ?s ?p ?x)) )",
               t_disjunction,
               "(disjunction ",
               "(assign ((?x <x>)) (bgp ( ?s ?p <x>)))",
               "(filter (!= ?x <y>) (bgp ( ?s ?p ?x)))",
            ")");
    }

    @Test public void disjunction03() {
        testOp("(filter (|| (!= ?x <x>) (= ?x <y>)) (bgp ( ?s ?p ?x)) )",
               t_disjunction,
               // Note - reordering of disjunction terms.
               "(disjunction ",
               "(assign ((?x <y>)) (bgp ( ?s ?p <y>)))",
               "(filter (!= ?x <x>) (bgp ( ?s ?p ?x)))",
            ")");
    }

    @Test public void disjunction04() {
        testOp("(filter (|| (!= ?x <y>) (!= ?x <x>)) (bgp ( ?s ?p ?x)) )",
               t_disjunction,
               (String[])null);
    }

    @Test public void disjunction05() {
        testOp("(filter (exprlist (|| (= ?x <y>) (!= ?x <x>)))    (bgp ( ?s ?p ?x)) )",
               t_disjunction,
               "  (disjunction",
               "    (assign ((?x <y>)) (bgp ( ?s ?p <y>)))",
               "    (filter (!= ?x <x>) (bgp ( ?s ?p ?x)))",
               ")"
            );
    }

    @Test public void disjunction06() {
        testOp("(filter (exprlist (lang ?x) (|| (= ?x <y>) (!= ?x <x>)))    (bgp ( ?s ?p ?x)) )",
               t_disjunction,
               "(filter (lang ?x)",
               "  (disjunction",
               "    (assign ((?x <y>)) (bgp ( ?s ?p <y>)))",
               "    (filter (!= ?x <x>) (bgp ( ?s ?p ?x)))",
               "))"
            );
    }

    @Test public void disjunction07() {
        testOp("(filter (exprlist (|| (= ?x <y>) (!= ?x <x>)) (lang ?x) )    (bgp ( ?s ?p ?x)) )",
               t_disjunction,
               "(filter (lang ?x)",
               "  (disjunction",
               "    (assign ((?x <y>)) (bgp ( ?s ?p <y>)))",
               "    (filter (!= ?x <x>) (bgp ( ?s ?p ?x)))",
               "))"
            );
    }

    @Test public void oneOf1() {
        testOp(
               "(filter (in ?x <x> 2 3) (bgp (?s ?p ?x)))",
               t_expandOneOf,
               "(filter (|| ( || (= ?x <x>) (= ?x 2)) (= ?x 3)) (bgp (?s ?p ?x)))");
    }

    @Test public void oneOf2() {
        testOp(
               "(filter (exprlist (= ?x 99) (in ?x <x> 2 3)) (bgp (?s ?p ?x)))",
               t_expandOneOf,
               "(filter (exprlist (= ?x 99) (|| ( || (= ?x <x>) (= ?x 2)) (= ?x 3))) (bgp (?s ?p ?x)))");
    }

    @Test public void oneOf3() {
        testOp(
               "(filter (notin ?x <x> 2 3) (bgp (?s ?p ?x)))",
               t_expandOneOf,
               "(filter (exprlist (!= ?x <x>) (!= ?x 2) (!= ?x 3)) (bgp (?s ?p ?x)))");
    }

    @Test
    public void oneOf4() {
        // JENA-771
        testOp("(filter true (distinct (filter (in ?x 1 2) (bgp (?s ?p ?x)) )))",
               t_expandOneOf,
               "(filter true (distinct (filter (|| (= ?x 1) (= ?x 2) ) (bgp (triple ?s ?p ?x)) )))");
    }

    @Test
    public void oneOf5() {
        // JENA-771
        testOp("(filter true (distinct (filter (notin ?x 1 2) (bgp (?s ?p ?x)) )))",
               t_expandOneOf,
               "(filter true (distinct (filter (exprlist (!= ?x 1) (!= ?x 2)) (bgp (triple ?s ?p ?x)) )))");
    }

    @Test
    public void oneOf6() {
        // JENA-1113
        int x = TransformExpandOneOf.REWRITE_LIMIT;
        try {
            TransformExpandOneOf.REWRITE_LIMIT = 3;
            testOp("(filter true (distinct (filter (notin ?x 1 2) (bgp (?s ?p ?x)) )))",
                   t_expandOneOf,
                "(filter true (distinct (filter (exprlist (!= ?x 1) (!= ?x 2)) (bgp (triple ?s ?p ?x)) )))");
            testOp("(filter true (distinct (filter (notin ?x 1 2 3) (bgp (?s ?p ?x)) )))",
                   t_expandOneOf,
                   // No change.
                   "(filter true (distinct (filter (notin ?x 1 2 3) (bgp (?s ?p ?x)) )))");

        } finally {
            TransformExpandOneOf.REWRITE_LIMIT = x;
        }
        // Check reset.
        testOp("(filter true (distinct (filter (notin ?x 1 2 3) (bgp (?s ?p ?x)) )))",
               t_expandOneOf,
               "(filter true (distinct (filter (exprlist (!= ?x 1) (!= ?x 2) (!= ?x 3)) (bgp (triple ?s ?p ?x)) )))");
    }


    @Test public void implicitJoin01() {
        testOp(
               "(filter (= ?x ?y) (bgp (?x ?p ?o)(?y ?p1 ?o1)))",
               t_implicitJoin,
               "(assign ((?x ?y)) (bgp (?y ?p ?o)(?y ?p1 ?o1)))");
    }

    // Test no longer appropriate.
    // LATERAL means the variables that are join-scope bound may have values at execution time.
//    @Test public void implicitJoin02() {
//        testOp(
//               "(filter (= ?x ?y) (bgp (?x ?p ?o)))",
//               t_implicitJoin,
//               "(table empty)");
//    }

    // LATERAL safe - no transformation.
    @Test public void implicitJoin02() {
        testOp(
               "(filter (= ?x ?y) (bgp (?x ?p ?o)))",
               t_implicitJoin,
               "(filter (= ?x ?y) (bgp (?x ?p ?o)))");
    }

    @Test public void implicitJoin03() {
        // Still safe to transform as at least one is guaranteed non-literal
        testOp(
               "(filter (= ?x ?y) (bgp (?x ?p ?o)(?a ?b ?y)))",
               t_implicitJoin,
               "(assign ((?x ?y)) (bgp (?y ?p ?o)(?a ?b ?y)))");
    }

    @Test public void implicitJoin04() {
        // Not safe to transform as both may be literals
        testOp(
               "(filter (= ?x ?y) (bgp (?a ?b ?x)(?c ?d ?y)))",
               t_implicitJoin,
               "(filter (= ?x ?y) (bgp (?a ?b ?x)(?c ?d ?y)))");
    }

    @Test public void implicitJoin05() {
        // Safe to transform as although both may be literals we are using sameTerm so already relying on term equality
        testOp(
               "(filter (sameTerm ?x ?y) (bgp (?a ?b ?x)(?c ?d ?y)))",
               t_implicitJoin,
               "(assign ((?x ?y)) (bgp (?a ?b ?y)(?c ?d ?y)))");
    }

    @Test public void implicitJoin06() {
        // Not safe to transform as equality on same variable
        testOp(
               "(filter (= ?x ?x) (bgp (?x ?p ?o)(?y ?p1 ?o1)))",
               t_implicitJoin,
               (String[])null);
    }

    @Test public void implicitJoin07() {
        testOp(
               "(filter ((= ?x ?y) (= ?x ?z)) (bgp (?x ?p ?o)(?y ?p1 ?z)))",
               t_implicitJoin,
               (String[])null);
    }

    @Test public void implicitJoin08() {
        testOp(
               "(filter (= ?x ?y) (join (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1))))",
               t_implicitJoin,
               "(assign ((?x ?y)) (join (bgp (?y ?p ?o)) (bgp (?y ?p1 ?o1))))");

        testOp(
               "(filter (= ?y ?x) (join (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1))))",
               t_implicitJoin,
               "(assign ((?y ?x)) (join (bgp (?x ?p ?o)) (bgp (?x ?p1 ?o1))))");
    }

    @Test public void implicitJoin09() {
        // A variable introduced by an assign cannot be considered safe
        testOp(
               "(filter (= ?x ?y) (assign ((?x <http://constant>)) (bgp (?y ?p ?o))))",
               t_implicitJoin,
               (String[])null);
    }

    @Test public void implicitJoin10() {
        // A variable not necessarily fixed makes the transform unsafe
        testOp(
               "(filter (= ?x ?y) (leftjoin (leftjoin (bgp (?s <http://pred> ?o)) (bgp (?x ?p ?o))) (bgp (?y ?p1 ?o1))))",
               t_implicitJoin,
               (String[])null);
    }

    // Test no longer appropriate.
    // LATERAL means the variables that are join-scope bound may have values at execution time.
//    @Test public void implictJoin11() {
//        // Test case related to JENA-500
//        // Detect that the expression (= ?prebound ?y) is always 'error' because
//        // ?prebound is undef.  Therefore the whole thing can be removed as there
//        // can be no solutions.
//        testOp(
//               "(filter (= ?prebound ?y) (extend ((?y (ex:someFunction ?x))) (table unit)))",
//               t_implicitJoin,
//               "(table empty)");
//    }

    // LATERAL safe - no "(table empty)" substitution.
    @Test public void implictJoin11() {
        testOp(
               "(filter (= ?prebound ?y) (extend ((?y (ex:someFunction ?x))) (table unit)))",
               t_implicitJoin,
               "(filter (= ?prebound ?y) (extend ((?y (ex:someFunction ?x))) (table unit)))");
    }


    @Test public void implicitJoin12() {
        // Test case from JENA-692
        // Implicit join should not apply to the whole union because the variables involved aren't fixed
        // However we can spot the special case of one branch of the union being invalid and throw it out
        testOp(
               "(filter (= ?a ?b) (union (bgp (triple ?a :p :o1)) (bgp (triple ?b :p ?a))))",
               t_implicitJoin,
               "(assign ((?a ?b)) (bgp (triple ?b :p ?b)))");
    }

    @Test public void implicitJoin13() {
        // Variation on test case from JENA-692
        // Implicit join should not apply to the whole union because the variables involved aren't fixed
        // However we can spot the special case of one branch of the union being invalid and throw it out
        testOp(
               "(filter (= ?a ?b) (union (bgp (triple ?b :p ?a)) (bgp (triple ?a :p :o1))))",
               t_implicitJoin,
               "(assign ((?a ?b)) (bgp (triple ?b :p ?b)))");
    }

    @Test public void implicitJoin14() {
        // Variation on test case from JENA-692
        // Implicit join should not apply to the whole union because the variables involved aren't fixed
        // However we can spot the special case where both branches are invalid
        testOp(
               "(filter (= ?a ?b) (union (bgp (triple ?b :p :o1)) (bgp (triple ?a :p :o2))))",
               t_implicitJoin,
               "(table empty)");
    }

    @Test public void implicitJoin15() {
        // Variation on the test case from JENA-692 with additional assignment added
        // Implicit join should not apply to the whole union because not all assignments are valid
        testOp(
               "(filter ((= ?a ?b) (= ?a ?p)) (union (bgp (triple ?a ?p :o1)) (bgp (triple ?b ?p ?a))))",
               t_implicitJoin,
               (String[])null);
    }

    @Test public void implicitJoin16() {
        // Variation on test case from JENA-692
        // Implicit join can apply because assignments are valid over both branches of the union
        testOp(
               "(filter (= ?a ?b) (union (bgp (triple ?a :p ?b)) (bgp (triple ?b :p ?a))))",
               t_implicitJoin,
               "(assign ((?a ?b)) (union (bgp (triple ?b :p ?b)) (bgp (triple ?b :p ?b))))");
    }

    @Test public void implicitJoin17() {
        // Variation on test case from JENA-692
        // Implicit join can apply because the filter is over the branch of the union where it is valid
        testOp(
               "(union (bgp (triple ?a :p :o1)) (filter (= ?a ?b) (bgp (triple ?b :p ?a))))",
               t_implicitJoin,
               "(union (bgp (triple ?a :p :o1)) (assign ((?a ?b)) (bgp (triple ?b :p ?b))))");
    }

    @Test public void implicitLeftJoin01() {
        // Possible to optimize some cases where it's an implicit left join

        // Covers the case with one variable on left and other on right
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))))");

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))))");
    }

    @Test public void implicitLeftJoin02() {
        // Possible to optimize some cases where it's an implicit left join

        // Covers the case with one variable on left and other on right
        testOp(
               "(leftjoin (bgp (?y ?p ?o)) (bgp (?x ?p1 ?o1)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?y ?p ?o)) (assign ((?x ?y)) (bgp (?y ?p1 ?o1))))");

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?y ?p ?o)) (bgp (?x ?p1 ?o1)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?y ?p ?o)) (assign ((?x ?y)) (bgp (?y ?p1 ?o1))))");
    }

    @Test public void implicitLeftJoin03() {
        // Possible to optimize some cases where it's an implicit left join

        // Covers the case with one variable on left and both on right
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?x <http://type> ?type)(?y ?p1 ?o1)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x <http://type> ?type)(?x ?p1 ?o1))))");

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?x <http://type> ?type)(?y ?p1 ?o1)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x <http://type> ?type)(?x ?p1 ?o1))))");
    }

    @Test public void implicitLeftJoin04() {
        // Possible to optimize some cases where it's an implicit left join

        // Covers the case with one variable on left and both on right
        testOp(
               "(leftjoin (bgp (?y ?p ?o)) (bgp (?x <http://type> ?type)(?y ?p1 ?o1)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?y ?p ?o)) (assign ((?x ?y)) (bgp (?y <http://type> ?type)(?y ?p1 ?o1))))");

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?y ?p ?o)) (bgp (?x <http://type> ?type)(?y ?p1 ?o1)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?y ?p ?o)) (assign ((?x ?y)) (bgp (?y <http://type> ?type)(?y ?p1 ?o1))))");
    }

    @Test public void implicitLeftJoin05() {
        // Possible to optimize some cases where it's an implicit left join

        // Covers the case of both variables on left and only one on right
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (bgp (?y ?p1 ?o1)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))))");

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (bgp (?y ?p1 ?o1)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))))");
    }

    @Test public void implicitLeftJoin06() {
        // Possible to optimize some cases where it's an implicit left join

        // Covers the case of both variables on left and only one on right
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (bgp (?x ?p1 ?o1)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (assign ((?x ?y)) (bgp (?y ?p1 ?o1))))");

        // Swapping the order of the equality expression should make no difference
        testOp("(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (bgp (?x ?p1 ?o1)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (assign ((?x ?y)) (bgp (?y ?p1 ?o1))))");
    }

    @Test public void implicitLeftJoin07() {
        // Possible to optimize some cases where it's an implicit left join

        // Covers the case of both variables on both sides
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (bgp (?x <http://type> ?type)(?y ?p1 ?o1)) ((= ?x ?y)))",
               t_implicitLeftJoin,
            "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (assign ((?x ?y)) (bgp (?y <http://type> ?type)(?y ?p1 ?o1))))");

        // Swapping the order of the equality expression will make a difference in this case
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (bgp (?x <http://type> ?type)(?y ?p1 ?o1)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (assign ((?y ?x)) (bgp (?x <http://type> ?type)(?x ?p1 ?o1))))");
    }

    @Test public void implicitLeftJoin08() {
        // We don't currently optimize the case where the filter will evaluate to false
        // for all solutions because neither variable in on the RHS
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (bgp (?a ?b ?c)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoin09() {
        // && means both conditions must hold so can optimize out the implicit join
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1)) (&& (= ?x ?y) (> ?o1 ?o2)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))) (> ?o1 ?o2))");

        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1)) (&& (> ?o1 ?o2) (= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))) (> ?o1 ?o2))");
    }

    @Test public void implicitLeftJoin10() {
        // Unsafe to optimize
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1)) (|| (= ?x ?y) (> ?o1 ?o2)))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoin11() {
        // Unsafe to optimize because cannot guarantee that substituted variable is fixed on RHS
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (leftjoin (bgp (?y ?p1 ?o1)) (bgp (?x ?p3 ?y))) (= ?x ?y))",
               t_implicitLeftJoin,
               (String[])null);

        // Swapping the order of equality expressions should still leave it unsafe
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (leftjoin (bgp (?y ?p1 ?o1)) (bgp (?x ?p3 ?y))) (= ?y ?x))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoin12() {
        // Unlike implicit join overlapping conditions can be safely optimized since the left join
        // optimizer is smart enough to apply the optimizations in an appropriate order
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((= ?x ?y) (= ?x ?z)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x))))");

        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((= ?y ?x) (= ?x ?z)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x))))");

        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((= ?x ?y) (= ?z ?x)))",
               t_implicitLeftJoin,
            "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x))))");
    }

    @Test public void implicitLeftJoin13() {
        // There are some overlapping conditions that are safe to optimize however they may end up introducing
        // additional unnecessary assign operators
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((= ?x ?y) (= ?x ?z) (= ?y ?z)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?z)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x)))))");

        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((= ?z ?y) (= ?x ?z) (= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?z ?x) (?y ?x)) (assign ((?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x)))))");

        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((= ?z ?y) (= ?z ?x) (= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?z ?x) (?y ?x)) (assign ((?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x)))))");
    }

    @Test public void implicitLeftJoin14() {
        // The optimizer is capable of eliminating the && entirely where appropriate
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((&& (= ?x ?y) (= ?x ?z))))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x))))");
    }

    @Test public void implicitLeftJoin15() {
        // The optimizer is capable of going any depth into nested && to find conditions to apply since it uses ExprList.splitConjunction()
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((&& (&& (= ?x ?y) (> ?o1 10)) (= ?x ?z))))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x))) (> ?o1 10))");

        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((&& (&& (> ?o1 10) (= ?x ?y)) (= ?x ?z))))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x))) (> ?o1 10))");
    }

    @Test public void implicitLeftJoin16() {
        // The optimizer is capable of going any depth into nested && to find conditions to apply since it uses ExprList.splitConjunction()
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((&& (&& (< ?o1 20) (&& (= ?x ?y) (> ?o1 10))) (= ?x ?z))))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x))) ((< ?o1 20) (> ?o1 10)))");
    }

    @Test public void implicitLeftJoin17() {
        // The optimizer is capable of going any depth into nested && to find conditions to apply since it uses ExprList.splitConjunction()
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((&& (&& (= ?x ?y) (> ?o1 10)) (< ?o1 20))))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?z))) ((> ?o1 10) (< ?o1 20)))");
    }

    @Test public void implicitLeftJoin18() {
        // The optimizer is capable of going any depth into nested && to find conditions to apply since it uses ExprList.splitConjunction()
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (bgp (?y ?p1 ?o1) (?y ?p2 ?z)) ((&& (&& (= ?x ?y) (= ?y ?z)) (= ?x ?z))))",
               t_implicitLeftJoin,
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x) (?z ?x)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1) (?x ?p2 ?x)))))");
    }

    @Test public void implicitLeftJoin19() {
        // Covers the case of both variables on left and neither on right
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (table unit) ((= ?x ?y)))",
               t_implicitLeftJoin,
               (String[])null);

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?x ?p ?o)(?x <http://pred> ?y)) (table unit) ((= ?y ?x)))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoin20() {
        // Covers the case of one variable on left and neither on right
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (table unit) ((= ?x ?y)))",
               t_implicitLeftJoin,
               (String[])null);

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (table unit) ((= ?y ?x)))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoin21() {
        // Covers the case of one variable on left and neither on right
        testOp(
               "(leftjoin (bgp (?y ?p ?o)) (table unit) ((= ?x ?y)))",
               t_implicitLeftJoin,
               (String[])null);

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?y ?p ?o)) (table unit) ((= ?y ?x)))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoin22() {
        // Covers the case of no variables actually being relevant
        testOp(
               "(leftjoin (bgp (?s ?p ?o)) (table unit) ((= ?x ?y)))",
               t_implicitLeftJoin,
               (String[])null);

        // Swapping the order of the equality expression should make no difference
        testOp(
               "(leftjoin (bgp (?s ?p ?o)) (table unit) ((= ?y ?x)))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoin23() {
        // Covers the case of neither variable on left and both on right
        testOp(
               "(leftjoin (table unit) (bgp (?x ?p ?o)(?x <http://pred> ?y)) ((= ?x ?y)))",
               t_implicitLeftJoin,
               "(leftjoin (table unit) (assign ((?x ?y)) (bgp (?y ?p ?o)(?y <http://pred> ?y))))");

        // Swapping the order of the equality will make a difference in this case
        testOp(
               "(leftjoin (table unit) (bgp (?x ?p ?o)(?x <http://pred> ?y)) ((= ?y ?x)))",
               t_implicitLeftJoin,
               "(leftjoin (table unit) (assign ((?y ?x)) (bgp (?x ?p ?o)(?x <http://pred> ?x))))");
    }

    @Test public void implicitLeftJoin24() {
        // Modified test case from JENA-692
        // Implicit join should not apply to the whole union because the variables involved aren't fixed
        testOp(
               "(leftjoin (bgp (triple ?a <http://type> ?type)) (union (bgp (triple ?a :p :o1)) (bgp (triple ?b :p ?a))) ((= ?a ?b)))",
               t_implicitLeftJoin,
               (String[])null);
    }

    @Test public void implicitLeftJoinConditional01() {
        // Can be optimized because not all assigns block linearization
        testOp(
               "(leftjoin (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))))",
               new TransformJoinStrategy(),
               "(conditional (bgp (?x ?p ?o)) (assign ((?y ?x)) (bgp (?x ?p1 ?o1))))");
    }

    @Test public void inequality01() {
        testOp("(filter (!= ?x <x>) (bgp ( ?s ?p ?x)) )",
               t_inequality,
               "(minus (bgp ( ?s ?p ?x)) (table (vars ?x) (row [?x <x>])))");
    }

    @Test public void inequality02() {
        // Not safe on strings
        testOp("(filter (!= ?x 'x') (bgp ( ?s ?p ?x)) )",
               t_inequality,
               (String[])null);
    }

    @Test public void inequality03() {
        // Not safe on numbers
        testOp("(filter (!= ?x 123) (bgp ( ?s ?p ?x)) )",
               t_inequality,
               (String[])null);
    }

    @Test public void inequality04() {
        // Unused
        testOp("(filter (!= ?UNUSED <x>) (bgp ( ?s ?p ?x)) )",
               t_inequality,
               "(table empty)");
    }

    @Test public void inequality05() {
        // Can't optimize if filter does not cover vars in LHS
        testOp("(filter (!= ?x2 <x>) (conditional (bgp ( ?s1 ?p1 ?x1))  (bgp ( ?s2 ?p2 ?x2))))",
               t_inequality,
               (String[])null);
    }

    @Test public void inequality06() {
        testOp("(filter (!= ?x <x>) (conditional (bgp ( ?s ?p ?x))  (bgp ( ?s ?p ?x))))",
               t_inequality,
               "(minus (conditional (bgp ( ?s ?p ?x))  (bgp ( ?s ?p ?x))) (table (vars ?x) (row [?x <x>])))");
    }

    @Test public void inequality07() {
        testOp("(filter (!= ?x <x>) (conditional (bgp ( ?s ?p ?x))  (bgp ( ?s ?p ?x1))))",
               t_inequality,
               "(minus (conditional (bgp ( ?s ?p ?x))  (bgp ( ?s ?p ?x1))) (table (vars ?x) (row [?x <x>])))");
    }

    @Test public void inequality08() {
        // Tests use of multiple != conditions on same variable
        testOp("(filter ((!= ?x <x>) (!= ?x <y>)) (bgp ( ?s ?p ?x)) )",
               t_inequality,
               "(minus (bgp (?s ?p ?x)) (table (vars ?x) (row [?x <x>]) (row [?x <y>])) )");
    }

    @Test public void inequality09() {
        // Tests use of multiple != conditions on different variables
        testOp("(filter ((!= ?x <x>) (!= ?p <y>)) (bgp ( ?s ?p ?x)) )",
               t_inequality,
               "(minus (bgp (?s ?p ?x)) (table (vars ?x ?p) (row [?x <x>])(row [?p <y>]) ))");
    }

    @Test public void inequality10() {
        // Tests use of multiple != conditions on both same and different variables
        testOp("(filter ((!= ?x <x>) (!= ?x <y>) (!= ?p <type>)) (bgp ( ?s ?p ?x)) )",
               t_inequality,
               "(minus (bgp (?s ?p ?x)) (table (vars ?x ?p) (row [?x <x>]) (row [?x <y>]) (row [?p <type>]) ))");
    }

    @Test public void inequality11() {
        // Other filter conditions should be preserved
        testOp("(filter ((!= ?x <x>) (> ?x 10)) (bgp ( ?s ?p ?x)) )",
               t_inequality,
               "(filter (> ?x 10) (minus (bgp ( ?s ?p ?x)) (table (vars ?x) (row [?x <x>]))))");
    }
}
