[CALCITE-6836] Add Rule to convert INTERSECT to EXISTS

core/src/main/java/org/apache/calcite/rel/rules/CoreRules.java

@@ -16,6 +16,7 @@
  */
 package org.apache.calcite.rel.rules;
 
+import org.apache.calcite.plan.RelOptUtil.Exists;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.core.Aggregate;
 import org.apache.calcite.rel.core.Calc;
@@ -348,6 +349,11 @@ private CoreRules() {}
   public static final IntersectToDistinctRule INTERSECT_TO_DISTINCT =
       IntersectToDistinctRule.Config.DEFAULT.toRule();
 
+  /** Rule that translates a {@link Intersect}
+   * into a {@link Exists} subquery. */
+  public static final IntersectToExistsRule INTERSECT_TO_EXISTS =
+      IntersectToExistsRule.Config.DEFAULT.toRule();
+
   /** Rule that translates a distinct
    * {@link Minus} into a group of operators
    * composed of {@link Union}, {@link Aggregate}, etc. */

core/src/main/java/org/apache/calcite/rel/rules/IntersectToExistsRule.java

@@ -0,0 +1,179 @@
+/*
+ * 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.calcite.rel.rules;
+
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.plan.RelOptUtil.Exists;
+import org.apache.calcite.plan.RelRule;
+import org.apache.calcite.plan.hep.HepRelVertex;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.core.CorrelationId;
+import org.apache.calcite.rel.core.Intersect;
+import org.apache.calcite.rel.logical.LogicalIntersect;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rel.type.RelDataTypeField;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.rex.RexSubQuery;
+import org.apache.calcite.rex.RexUtil;
+import org.apache.calcite.sql.fun.SqlStdOperatorTable;
+import org.apache.calcite.tools.RelBuilder;
+import org.apache.calcite.tools.RelBuilderFactory;
+import org.apache.calcite.util.ImmutableBitSet;
+
+import com.google.common.collect.ImmutableSet;
+
+import org.immutables.value.Value;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Planner rule that translates a {@link Intersect}
+ * (<code>all</code> = <code>false</code>)
+ * into a {@link Exists}.
+ *
+ * @see CoreRules#INTERSECT_TO_EXISTS
+ */
+@Value.Enclosing
+public class IntersectToExistsRule
+    extends RelRule<IntersectToExistsRule.Config>
+    implements TransformationRule {
+
+  /** Creates an IntersectToExistRule. */
+  protected IntersectToExistsRule(Config config) {
+    super(config);
+  }
+
+  @Deprecated // to be removed before 2.0
+  public IntersectToExistsRule(Class<? extends Intersect> intersectClass,
+      RelBuilderFactory relBuilderFactory) {
+    this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
+        .as(Config.class)
+        .withOperandFor(intersectClass));
+  }
+
+  //~ Methods ----------------------------------------------------------------
+
+  @Override public void onMatch(RelOptRuleCall call) {
+    final Intersect intersect = call.rel(0);
+    if (intersect.all) {
+      return; // nothing we can do
+    }
+
+    final RelBuilder builder = call.builder();
+    final RexBuilder rexBuilder = builder.getRexBuilder();
+
+    RelDataType rowType = intersect.getRowType();
+    List<RelNode> inputs = intersect.getInputs();
+    RelNode current = inputs.get(0);
+
+    // get all column indices of intersect
+    ImmutableBitSet fieldIndices = ImmutableBitSet.of(rowType.getFieldList()
+        .stream().map(RelDataTypeField::getIndex)
+        .collect(Collectors.toList()));
+
+    // iterate over the inputs and apply exists subquery
+    for (int i = 1; i < inputs.size(); i++) {
+      RelNode nextInput = removeHepRelVertex(inputs.get(i));
+
+      // create correlation
+      CorrelationId correlationId = intersect.getCluster().createCorrel();
+      RexNode correl =
+          rexBuilder.makeCorrel(rowType, correlationId);
+
+      // create condition in exists filter, and use correlation
+      List<RexNode> conditions = new ArrayList<>();
+      for (int fieldIndex : fieldIndices) {
+        RexNode outerField = rexBuilder.makeInputRef(rowType, fieldIndex);
+        RexNode innerField = rexBuilder.makeFieldAccess(correl, fieldIndex);
+        conditions.add(
+            rexBuilder.makeCall(SqlStdOperatorTable.IS_NOT_DISTINCT_FROM,
+                outerField, innerField));
+      }
+      RexNode condition = RexUtil.composeConjunction(rexBuilder, conditions);
+
+      // build exists subquery
+      RelNode existsSubQuery = builder.push(nextInput)
+          .filter(condition)
+          .project(builder.fields(fieldIndices))
+          .build();
+
+      // apply exists subquery to the current relation
+      current = builder.push(current)
+          .filter(ImmutableSet.of(correlationId),
+              RexSubQuery.exists(existsSubQuery))
+          .build();
+    }
+
+    builder.push(current);
+    List<RexNode> projects = new ArrayList<>();
+    for (int fieldIndex : fieldIndices) {
+      RexNode rexNode = builder.fields().get(fieldIndex);
+      RelDataType originalType =
+          rowType.getFieldList().get(projects.size()).getType();
+      RexNode expr;
+      if (!originalType.equals(rexNode.getType())) {
+        expr = rexBuilder.makeCast(originalType, rexNode, true, false);
+      } else {
+        expr = rexNode;
+      }
+      projects.add(expr);
+    }
+
+    RelNode result = builder.project(projects)
+        .distinct()
+        .build();
+
+    call.transformTo(result);
+  }
+
+  /**
+   * Will not eliminate HepRelVertex in subqueries
+   * during the optimization process.
+   * We need to eliminate it here. */
+  private RelNode removeHepRelVertex(RelNode input) {
+    if (input instanceof HepRelVertex) {
+      HepRelVertex hepRelVertex = (HepRelVertex) input;
+      RelNode currentRel = hepRelVertex.getCurrentRel();
+      return removeHepRelVertex(currentRel);
+    }
+    List<RelNode> newInputs = new ArrayList<>();
+    for (RelNode child : input.getInputs()) {
+      newInputs.add(removeHepRelVertex(child));
+    }
+    return input.copy(input.getTraitSet(), newInputs);
+  }
+
+  /** Rule configuration. */
+  @Value.Immutable
+  public interface Config extends RelRule.Config {
+    Config DEFAULT = ImmutableIntersectToExistsRule.Config.of()
+        .withOperandFor(LogicalIntersect.class);
+
+    @Override default IntersectToExistsRule toRule() {
+      return new IntersectToExistsRule(this);
+    }
+
+    /** Defines an operand tree for the given classes. */
+    default Config withOperandFor(Class<? extends Intersect> intersectClass) {
+      return withOperandSupplier(b -> b.operand(intersectClass).anyInputs())
+          .as(Config.class);
+    }
+  }
+}

core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java

@@ -37,6 +37,7 @@
 import org.apache.calcite.rel.rules.AggregateProjectMergeRule;
 import org.apache.calcite.rel.rules.CoreRules;
 import org.apache.calcite.rel.rules.FilterJoinRule;
+import org.apache.calcite.rel.rules.IntersectToExistsRule;
 import org.apache.calcite.rel.rules.ProjectOverSumToSum0Rule;
 import org.apache.calcite.rel.rules.ProjectToWindowRule;
 import org.apache.calcite.rel.rules.PruneEmptyRules;
@@ -244,6 +245,33 @@ private static String toSql(RelNode root, SqlDialect dialect,
     sql(query).withMysql().ok(expected);
   }
 
+  /**
+   * Test case of
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-6836">[CALCITE-6836]
+   * Add Rule to convert INTERSECT to EXISTS</a>. */
+  @Test void testIntersectToExistsRule() {
+    String query = "SELECT \"product_name\"\n"
+            + "FROM \"foodmart\".\"product\"\n"
+            + "INTERSECT\n"
+            + "SELECT \"product_name\"\n"
+            + "FROM \"foodmart\".\"product\"";
+    String expected = "SELECT `product_name`\n"
+            + "FROM (SELECT `product_name`\n"
+            + "FROM `foodmart`.`product`) AS `t`\n"
+            + "WHERE EXISTS (SELECT *\n"
+            + "FROM (SELECT `product_name`\n"
+            + "FROM `foodmart`.`product`) AS `t0`\n"
+            + "WHERE `product_name` IS NOT DISTINCT FROM `t`.`product_name`)\n"
+            + "GROUP BY `product_name`";
+    HepProgramBuilder builder = new HepProgramBuilder();
+    builder.addRuleClass(IntersectToExistsRule.class);
+    HepPlanner hepPlanner = new HepPlanner(builder.build());
+    RuleSet rules =
+            RuleSets.ofList(CoreRules.INTERSECT_TO_EXISTS);
+
+    sql(query).withMysql().optimize(rules, hepPlanner).ok(expected);
+  }
+
   @Test void testGroupByBooleanLiteral() {
     String query = "select avg(\"salary\") from \"employee\" group by true";
     String expectedRedshift = "SELECT AVG(\"employee\".\"salary\")\n"

core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java

@@ -9716,4 +9716,50 @@ private void checkJoinAssociateRuleWithTopAlwaysTrueCondition(boolean allowAlway
     fixture().withRelBuilderConfig(a -> a.withBloat(-1))
         .relFn(relFn).withPlanner(planner).check();
   }
+
+  /**
+   * Test case of
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-6836">[CALCITE-6836]
+   * Add Rule to convert INTERSECT to EXISTS</a>. */
+  @Test void testIntersectToExistsRuleOneField() {
+    String sql = "SELECT a.ename FROM emp AS a\n"
+        + "INTERSECT\n"
+        + "SELECT b.name FROM dept AS b";
+    sql(sql).withRule(CoreRules.INTERSECT_TO_EXISTS)
+        .check();
+  }
+
+  @Test void testIntersectToExistsRulePrimaryKey() {
+    String sql = "SELECT a.empno FROM emp AS a\n"
+        + "INTERSECT\n"
+        + "SELECT b.empno FROM emp AS b";
+    sql(sql).withRule(CoreRules.INTERSECT_TO_EXISTS)
+        .check();
+  }
+
+  @Test void testIntersectToExistsRuleMultiFields() {
+    String sql = "SELECT a.ename, a.job FROM emp AS a\n"
+        + "INTERSECT\n"
+        + "SELECT b.ename, b.job FROM emp AS b";
+    sql(sql).withRule(CoreRules.INTERSECT_TO_EXISTS)
+        .check();
+  }
+
+  @Test void testIntersectToExistsRuleMultiIntersect() {
+    String sql = "SELECT a.ename FROM emp AS a\n"
+        + "INTERSECT\n"
+        + "SELECT b.name FROM dept AS b\n"
+        + "INTERSECT\n"
+        + "SELECT c.ename FROM emp AS c";
+    sql(sql).withRule(CoreRules.INTERSECT_TO_EXISTS)
+        .check();
+  }
+
+  @Test void testIntersectToExistsRuleWithAll() {
+    String sql = "SELECT a.ename FROM emp AS a\n"
+        + "INTERSECT ALL\n"
+        + "SELECT b.name FROM dept AS b";
+    sql(sql).withRule(CoreRules.INTERSECT_TO_EXISTS)
+        .checkUnchanged();
+  }
 }