com.hazelcast.org.apache.calcite.rel.rules.JoinToCorrelateRule Maven / Gradle / Ivy
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* 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 com.hazelcast.com.liance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.com.hazelcast.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 com.hazelcast.org.apache.calcite.rel.rules;
import com.hazelcast.org.apache.calcite.plan.Contexts;
import com.hazelcast.org.apache.calcite.plan.RelOptCluster;
import com.hazelcast.org.apache.calcite.plan.RelOptRule;
import com.hazelcast.org.apache.calcite.plan.RelOptRuleCall;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.core.CorrelationId;
import com.hazelcast.org.apache.calcite.rel.core.Join;
import com.hazelcast.org.apache.calcite.rel.core.RelFactories;
import com.hazelcast.org.apache.calcite.rel.logical.LogicalCorrelate;
import com.hazelcast.org.apache.calcite.rel.logical.LogicalJoin;
import com.hazelcast.org.apache.calcite.rex.RexBuilder;
import com.hazelcast.org.apache.calcite.rex.RexInputRef;
import com.hazelcast.org.apache.calcite.rex.RexNode;
import com.hazelcast.org.apache.calcite.rex.RexShuttle;
import com.hazelcast.org.apache.calcite.tools.RelBuilder;
import com.hazelcast.org.apache.calcite.tools.RelBuilderFactory;
import com.hazelcast.org.apache.calcite.util.ImmutableBitSet;
/**
* Rule that converts a {@link com.hazelcast.org.apache.calcite.rel.core.Join}
* into a {@link com.hazelcast.org.apache.calcite.rel.logical.LogicalCorrelate}, which can
* then be implemented using nested loops.
*
* For example,
*
* select * from emp join dept on emp.deptno =
* dept.deptno
*
* becomes a Correlator which restarts LogicalTableScan("DEPT") for each
* row read from LogicalTableScan("EMP").
*
* This rule is not applicable if for certain types of outer join. For
* example,
*
* select * from emp right join dept on emp.deptno =
* dept.deptno
*
* would require emitting a NULL emp row if a certain department contained no
* employees, and Correlator cannot do that.
*/
public class JoinToCorrelateRule extends RelOptRule implements TransformationRule {
//~ Static fields/initializers ---------------------------------------------
/**
* Rule that converts a {@link com.hazelcast.org.apache.calcite.rel.logical.LogicalJoin}
* into a {@link com.hazelcast.org.apache.calcite.rel.logical.LogicalCorrelate}
*/
public static final JoinToCorrelateRule INSTANCE =
new JoinToCorrelateRule(LogicalJoin.class, RelFactories.LOGICAL_BUILDER,
"JoinToCorrelateRule");
/** Synonym for {@link #INSTANCE};
* {@code JOIN} is not deprecated, but {@code INSTANCE} is preferred. */
public static final JoinToCorrelateRule JOIN = INSTANCE;
//~ Constructors -----------------------------------------------------------
/**
* Creates a rule that converts a {@link com.hazelcast.org.apache.calcite.rel.logical.LogicalJoin}
* into a {@link com.hazelcast.org.apache.calcite.rel.logical.LogicalCorrelate}
*/
public JoinToCorrelateRule(RelBuilderFactory relBuilderFactory) {
this(LogicalJoin.class, relBuilderFactory, null);
}
@Deprecated // to be removed before 2.0
protected JoinToCorrelateRule(RelFactories.FilterFactory filterFactory) {
this(RelBuilder.proto(Contexts.of(filterFactory)));
}
/**
* Creates a JoinToCorrelateRule for a certain sub-class of
* {@link com.hazelcast.org.apache.calcite.rel.core.Join} to be transformed into a
* {@link com.hazelcast.org.apache.calcite.rel.logical.LogicalCorrelate}.
*
* @param clazz Class of relational expression to match (must not be null)
* @param relBuilderFactory Builder for relational expressions
* @param description Description, or null to guess description
*/
private JoinToCorrelateRule(Class clazz,
RelBuilderFactory relBuilderFactory,
String description) {
super(operand(clazz, any()), relBuilderFactory, description);
}
//~ Methods ----------------------------------------------------------------
public boolean matches(RelOptRuleCall call) {
Join join = call.rel(0);
return !join.getJoinType().generatesNullsOnLeft();
}
public void onMatch(RelOptRuleCall call) {
assert matches(call);
final Join join = call.rel(0);
RelNode right = join.getRight();
final RelNode left = join.getLeft();
final int leftFieldCount = left.getRowType().getFieldCount();
final RelOptCluster cluster = join.getCluster();
final RexBuilder rexBuilder = cluster.getRexBuilder();
final RelBuilder relBuilder = call.builder();
final CorrelationId correlationId = cluster.createCorrel();
final RexNode corrVar =
rexBuilder.makeCorrel(left.getRowType(), correlationId);
final ImmutableBitSet.Builder requiredColumns = ImmutableBitSet.builder();
// Replace all references of left input with FieldAccess(corrVar, field)
final RexNode joinCondition = join.getCondition().accept(new RexShuttle() {
@Override public RexNode visitInputRef(RexInputRef input) {
int field = input.getIndex();
if (field >= leftFieldCount) {
return rexBuilder.makeInputRef(input.getType(),
input.getIndex() - leftFieldCount);
}
requiredColumns.set(field);
return rexBuilder.makeFieldAccess(corrVar, field);
}
});
relBuilder.push(right).filter(joinCondition);
RelNode newRel =
LogicalCorrelate.create(left,
relBuilder.build(),
correlationId,
requiredColumns.build(),
join.getJoinType());
call.transformTo(newRel);
}
}