com.hazelcast.org.apache.calcite.rel.rules.SubQueryRemoveRule Maven / Gradle / Ivy
/*
* 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.RelOptRule;
import com.hazelcast.org.apache.calcite.plan.RelOptRuleCall;
import com.hazelcast.org.apache.calcite.plan.RelOptRuleOperand;
import com.hazelcast.org.apache.calcite.plan.RelOptUtil;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.core.Correlate;
import com.hazelcast.org.apache.calcite.rel.core.CorrelationId;
import com.hazelcast.org.apache.calcite.rel.core.Filter;
import com.hazelcast.org.apache.calcite.rel.core.Join;
import com.hazelcast.org.apache.calcite.rel.core.JoinRelType;
import com.hazelcast.org.apache.calcite.rel.core.Project;
import com.hazelcast.org.apache.calcite.rel.core.RelFactories;
import com.hazelcast.org.apache.calcite.rel.metadata.RelMetadataQuery;
import com.hazelcast.org.apache.calcite.rex.LogicVisitor;
import com.hazelcast.org.apache.calcite.rex.RexCorrelVariable;
import com.hazelcast.org.apache.calcite.rex.RexInputRef;
import com.hazelcast.org.apache.calcite.rex.RexLiteral;
import com.hazelcast.org.apache.calcite.rex.RexNode;
import com.hazelcast.org.apache.calcite.rex.RexShuttle;
import com.hazelcast.org.apache.calcite.rex.RexSubQuery;
import com.hazelcast.org.apache.calcite.rex.RexUtil;
import com.hazelcast.org.apache.calcite.sql.SqlAggFunction;
import com.hazelcast.org.apache.calcite.sql.SqlKind;
import com.hazelcast.org.apache.calcite.sql.fun.SqlQuantifyOperator;
import com.hazelcast.org.apache.calcite.sql.fun.SqlStdOperatorTable;
import com.hazelcast.org.apache.calcite.sql2rel.RelDecorrelator;
import com.hazelcast.org.apache.calcite.tools.RelBuilder;
import com.hazelcast.org.apache.calcite.tools.RelBuilderFactory;
import com.hazelcast.org.apache.calcite.util.ImmutableBitSet;
import com.hazelcast.org.apache.calcite.util.Pair;
import com.hazelcast.org.apache.calcite.util.Util;
import com.hazelcast.com.google.com.hazelcast.com.on.collect.ImmutableList;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
/**
* Transform that converts IN, EXISTS and scalar sub-queries into joins.
*
* Sub-queries are represented by {@link RexSubQuery} expressions.
*
*
A sub-query may or may not be correlated. If a sub-query is correlated,
* the wrapped {@link RelNode} will contain a {@link RexCorrelVariable} before
* the rewrite, and the product of the rewrite will be a {@link Correlate}.
* The Correlate can be removed using {@link RelDecorrelator}.
*/
public abstract class SubQueryRemoveRule extends RelOptRule implements TransformationRule {
public static final SubQueryRemoveRule PROJECT =
new SubQueryProjectRemoveRule(RelFactories.LOGICAL_BUILDER);
public static final SubQueryRemoveRule FILTER =
new SubQueryFilterRemoveRule(RelFactories.LOGICAL_BUILDER);
public static final SubQueryRemoveRule JOIN =
new SubQueryJoinRemoveRule(RelFactories.LOGICAL_BUILDER);
/**
* Creates a SubQueryRemoveRule.
*
* @param operand root operand, must not be null
* @param description Description, or null to guess description
* @param relBuilderFactory Builder for relational expressions
*/
public SubQueryRemoveRule(RelOptRuleOperand operand,
RelBuilderFactory relBuilderFactory,
String description) {
super(operand, relBuilderFactory, description);
}
protected RexNode apply(RexSubQuery e, Set variablesSet,
RelOptUtil.Logic logic,
RelBuilder builder, int inputCount, int offset) {
switch (e.getKind()) {
case SCALAR_QUERY:
return rewriteScalarQuery(e, variablesSet, builder, inputCount, offset);
case SOME:
return rewriteSome(e, variablesSet, builder);
case IN:
return rewriteIn(e, variablesSet, logic, builder, offset);
case EXISTS:
return rewriteExists(e, variablesSet, logic, builder);
default:
throw new AssertionError(e.getKind());
}
}
/**
* Rewrites a scalar sub-query into an
* {@link com.hazelcast.org.apache.calcite.rel.core.Aggregate}.
*
* @param e IN sub-query to rewrite
* @param variablesSet A set of variables used by a relational
* expression of the specified RexSubQuery
* @param builder Builder
* @param offset Offset to shift {@link RexInputRef}
*
* @return Expression that may be used to replace the RexSubQuery
*/
private RexNode rewriteScalarQuery(RexSubQuery e, Set variablesSet,
RelBuilder builder, int inputCount, int offset) {
builder.push(e.rel);
final RelMetadataQuery mq = e.rel.getCluster().getMetadataQuery();
final Boolean unique = mq.areColumnsUnique(builder.peek(),
ImmutableBitSet.of());
if (unique == null || !unique) {
builder.aggregate(builder.groupKey(),
builder.aggregateCall(SqlStdOperatorTable.SINGLE_VALUE,
builder.field(0)));
}
builder.join(JoinRelType.LEFT, builder.literal(true), variablesSet);
return field(builder, inputCount, offset);
}
/**
* Rewrites a SOME sub-query into a {@link Join}.
*
* @param e SOME sub-query to rewrite
* @param builder Builder
*
* @return Expression that may be used to replace the RexSubQuery
*/
private RexNode rewriteSome(RexSubQuery e, Set variablesSet,
RelBuilder builder) {
// Most general case, where the left and right keys might have nulls, and
// caller requires 3-valued logic return.
//
// select e.deptno, e.deptno < some (select deptno from emp) as v
// from emp as e
//
// becomes
//
// select e.deptno,
// case
// when q.c = 0 then false // sub-query is empty
// when (e.deptno < q.m) is true then true
// when q.c > q.d then unknown // sub-query has at least one null
// else e.deptno < q.m
// end as v
// from emp as e
// cross join (
// select max(deptno) as m, count(*) as c, count(deptno) as d
// from emp) as q
//
final SqlQuantifyOperator op = (SqlQuantifyOperator) e.op;
// SOME_EQ & SOME_NE should have been rewritten into IN/ NOT IN
assert op == SqlStdOperatorTable.SOME_GE || op == SqlStdOperatorTable.SOME_LE
|| op == SqlStdOperatorTable.SOME_LT || op == SqlStdOperatorTable.SOME_GT;
final RexNode caseRexNode;
final RexNode literalFalse = builder.literal(false);
final RexNode literalTrue = builder.literal(true);
final RexLiteral literalUnknown =
builder.getRexBuilder().makeNullLiteral(literalFalse.getType());
final SqlAggFunction minMax = op.com.hazelcast.com.arisonKind == SqlKind.GREATER_THAN
|| op.com.hazelcast.com.arisonKind == SqlKind.GREATER_THAN_OR_EQUAL
? SqlStdOperatorTable.MIN
: SqlStdOperatorTable.MAX;
if (variablesSet.isEmpty()) {
// for non-correlated case queries such as
// select e.deptno, e.deptno < some (select deptno from emp) as v
// from emp as e
//
// becomes
//
// select e.deptno,
// case
// when q.c = 0 then false // sub-query is empty
// when (e.deptno < q.m) is true then true
// when q.c > q.d then unknown // sub-query has at least one null
// else e.deptno < q.m
// end as v
// from emp as e
// cross join (
// select max(deptno) as m, count(*) as c, count(deptno) as d
// from emp) as q
builder.push(e.rel)
.aggregate(builder.groupKey(),
builder.aggregateCall(minMax, builder.field(0)).as("m"),
builder.count(false, "c"),
builder.count(false, "d", builder.field(0)))
.as("q")
.join(JoinRelType.INNER);
caseRexNode = builder.call(SqlStdOperatorTable.CASE,
builder.call(SqlStdOperatorTable.EQUALS, builder.field("q", "c"),
builder.literal(0)),
literalFalse,
builder.call(SqlStdOperatorTable.IS_TRUE,
builder.call(RelOptUtil.op(op.com.hazelcast.com.arisonKind, null),
e.operands.get(0), builder.field("q", "m"))),
literalTrue,
builder.call(SqlStdOperatorTable.GREATER_THAN,
builder.field("q", "c"), builder.field("q", "d")),
literalUnknown,
builder.call(RelOptUtil.op(op.com.hazelcast.com.arisonKind, null),
e.operands.get(0), builder.field("q", "m")));
} else {
// for correlated case queries such as
//
// select e.deptno, e.deptno < some (
// select deptno from emp where emp.name = e.name) as v
// from emp as e
//
// becomes
//
// select e.deptno,
// case
// when indicator is null then false // sub-query is empty for corresponding corr value
// when q.c = 0 then false // sub-query is empty
// when (e.deptno < q.m) is true then true
// when q.c > q.d then unknown // sub-query has at least one null
// else e.deptno < q.m
// end as v
// from emp as e
// left outer join (
// select name, max(deptno) as m, count(*) as c, count(deptno) as d,
// "alwaysTrue" as indicator
// from emp group by name) as q on e.name = q.name
builder.push(e.rel)
.aggregate(builder.groupKey(),
builder.aggregateCall(minMax, builder.field(0)).as("m"),
builder.count(false, "c"),
builder.count(false, "d", builder.field(0)));
final List parentQueryFields = new ArrayList<>();
parentQueryFields.addAll(builder.fields());
String indicator = "trueLiteral";
parentQueryFields.add(builder.alias(literalTrue, indicator));
builder.project(parentQueryFields).as("q");
builder.join(JoinRelType.LEFT, literalTrue, variablesSet);
caseRexNode = builder.call(SqlStdOperatorTable.CASE,
builder.call(SqlStdOperatorTable.IS_NULL,
builder.field("q", indicator)),
literalFalse,
builder.call(SqlStdOperatorTable.EQUALS, builder.field("q", "c"),
builder.literal(0)),
literalFalse,
builder.call(SqlStdOperatorTable.IS_TRUE,
builder.call(RelOptUtil.op(op.com.hazelcast.com.arisonKind, null),
e.operands.get(0), builder.field("q", "m"))),
literalTrue,
builder.call(SqlStdOperatorTable.GREATER_THAN,
builder.field("q", "c"), builder.field("q", "d")),
literalUnknown,
builder.call(RelOptUtil.op(op.com.hazelcast.com.arisonKind, null),
e.operands.get(0), builder.field("q", "m")));
}
// CASE statement above is created with nullable boolean type, but it might
// not be correct. If the original sub-query node's type is not nullable it
// is guaranteed for case statement to not produce NULLs. Therefore to avoid
// planner com.hazelcast.com.laining we need to add cast. Note that nullable type is
// created due to the MIN aggregate call, since there is no GROUP BY.
if (!e.getType().isNullable()) {
return builder.cast(caseRexNode, e.getType().getSqlTypeName());
}
return caseRexNode;
}
/**
* Rewrites an EXISTS RexSubQuery into a {@link Join}.
*
* @param e EXISTS sub-query to rewrite
* @param variablesSet A set of variables used by a relational
* expression of the specified RexSubQuery
* @param logic Logic for evaluating
* @param builder Builder
*
* @return Expression that may be used to replace the RexSubQuery
*/
private RexNode rewriteExists(RexSubQuery e, Set variablesSet,
RelOptUtil.Logic logic, RelBuilder builder) {
builder.push(e.rel);
builder.project(builder.alias(builder.literal(true), "i"));
switch (logic) {
case TRUE:
// Handles queries with single EXISTS in filter condition:
// select e.deptno from emp as e
// where exists (select deptno from emp)
builder.aggregate(builder.groupKey(0));
builder.as("dt");
builder.join(JoinRelType.INNER, builder.literal(true), variablesSet);
return builder.literal(true);
default:
builder.distinct();
}
builder.as("dt");
builder.join(JoinRelType.LEFT, builder.literal(true), variablesSet);
return builder.isNotNull(Util.last(builder.fields()));
}
/**
* Rewrites an IN RexSubQuery into a {@link Join}.
*
* @param e IN sub-query to rewrite
* @param variablesSet A set of variables used by a relational
* expression of the specified RexSubQuery
* @param logic Logic for evaluating
* @param builder Builder
* @param offset Offset to shift {@link RexInputRef}
*
* @return Expression that may be used to replace the RexSubQuery
*/
private RexNode rewriteIn(RexSubQuery e, Set variablesSet,
RelOptUtil.Logic logic, RelBuilder builder, int offset) {
// Most general case, where the left and right keys might have nulls, and
// caller requires 3-valued logic return.
//
// select e.deptno, e.deptno in (select deptno from emp)
// from emp as e
//
// becomes
//
// select e.deptno,
// case
// when ct.c = 0 then false
// when e.deptno is null then null
// when dt.i is not null then true
// when ct.ck < ct.c then null
// else false
// end
// from emp as e
// left join (
// (select count(*) as c, count(deptno) as ck from emp) as ct
// cross join (select distinct deptno, true as i from emp)) as dt
// on e.deptno = dt.deptno
//
// If keys are not null we can remove "ct" and simplify to
//
// select e.deptno,
// case
// when dt.i is not null then true
// else false
// end
// from emp as e
// left join (select distinct deptno, true as i from emp) as dt
// on e.deptno = dt.deptno
//
// We could further simplify to
//
// select e.deptno,
// dt.i is not null
// from emp as e
// left join (select distinct deptno, true as i from emp) as dt
// on e.deptno = dt.deptno
//
// but have not yet.
//
// If the logic is TRUE we can just kill the record if the condition
// evaluates to FALSE or UNKNOWN. Thus the query simplifies to an inner
// join:
//
// select e.deptno,
// true
// from emp as e
// inner join (select distinct deptno from emp) as dt
// on e.deptno = dt.deptno
//
builder.push(e.rel);
final List fields = new ArrayList<>(builder.fields());
// for the case when IN has only literal operands, it may be handled
// in the simpler way:
//
// select e.deptno, 123456 in (select deptno from emp)
// from emp as e
//
// becomes
//
// select e.deptno,
// case
// when dt.c IS NULL THEN FALSE
// when e.deptno IS NULL THEN NULL
// when dt.cs IS FALSE THEN NULL
// when dt.cs IS NOT NULL THEN TRUE
// else false
// end
// from emp AS e
// cross join (
// select distinct deptno is not null as cs, count(*) as c
// from emp
// where deptno = 123456 or deptno is null or e.deptno is null
// order by cs desc limit 1) as dt
//
boolean allLiterals = RexUtil.allLiterals(e.getOperands());
final List expressionOperands = new ArrayList<>(e.getOperands());
final List keyIsNulls = e.getOperands().stream()
.filter(operand -> operand.getType().isNullable())
.map(builder::isNull)
.collect(Collectors.toList());
final RexLiteral trueLiteral = (RexLiteral) builder.literal(true);
final RexLiteral falseLiteral = (RexLiteral) builder.literal(false);
final RexLiteral unknownLiteral =
builder.getRexBuilder().makeNullLiteral(trueLiteral.getType());
if (allLiterals) {
final List conditions =
Pair.zip(expressionOperands, fields).stream()
.map(pair -> builder.equals(pair.left, pair.right))
.collect(Collectors.toList());
switch (logic) {
case TRUE:
case TRUE_FALSE:
builder.filter(conditions);
builder.project(builder.alias(trueLiteral, "cs"));
builder.distinct();
break;
default:
List isNullOpperands = fields.stream()
.map(builder::isNull)
.collect(Collectors.toList());
// uses keyIsNulls conditions in the filter to avoid empty results
isNullOpperands.addAll(keyIsNulls);
builder.filter(
builder.or(
builder.and(conditions),
builder.or(isNullOpperands)));
RexNode project = builder.and(
fields.stream()
.map(builder::isNotNull)
.collect(Collectors.toList()));
builder.project(builder.alias(project, "cs"));
if (variablesSet.isEmpty()) {
builder.aggregate(builder.groupKey(builder.field("cs")),
builder.count(false, "c"));
// sorts input with desc order since we are interested
// only in the case when one of the values is true.
// When true value is absent then we are interested
// only in false value.
builder.sortLimit(0, 1,
ImmutableList.of(
builder.call(SqlStdOperatorTable.DESC,
builder.field("cs"))));
} else {
builder.distinct();
}
}
// clears expressionOperands and fields lists since
// all expressions were used in the filter
expressionOperands.clear();
fields.clear();
} else {
switch (logic) {
case TRUE:
builder.aggregate(builder.groupKey(fields));
break;
case TRUE_FALSE_UNKNOWN:
case UNKNOWN_AS_TRUE:
// Builds the cross join
builder.aggregate(builder.groupKey(),
builder.count(false, "c"),
builder.count(builder.fields()).as("ck"));
builder.as("ct");
if (!variablesSet.isEmpty()) {
builder.join(JoinRelType.LEFT, trueLiteral, variablesSet);
} else {
builder.join(JoinRelType.INNER, trueLiteral, variablesSet);
}
offset += 2;
builder.push(e.rel);
// fall through
default:
fields.add(builder.alias(trueLiteral, "i"));
builder.project(fields);
builder.distinct();
}
}
builder.as("dt");
int refOffset = offset;
final List conditions =
Pair.zip(expressionOperands, builder.fields()).stream()
.map(pair -> builder.equals(pair.left, RexUtil.shift(pair.right, refOffset)))
.collect(Collectors.toList());
switch (logic) {
case TRUE:
builder.join(JoinRelType.INNER, builder.and(conditions), variablesSet);
return trueLiteral;
}
// Now the left join
builder.join(JoinRelType.LEFT, builder.and(conditions), variablesSet);
final ImmutableList.Builder operands = ImmutableList.builder();
RexLiteral b = trueLiteral;
switch (logic) {
case TRUE_FALSE_UNKNOWN:
b = unknownLiteral;
// fall through
case UNKNOWN_AS_TRUE:
if (allLiterals) {
// Considers case when right side of IN is empty
// for the case of non-correlated sub-queries
if (variablesSet.isEmpty()) {
operands.add(
builder.isNull(builder.field("c")),
falseLiteral);
}
operands.add(
builder.equals(builder.field("cs"), falseLiteral),
b);
} else {
operands.add(
builder.equals(builder.field("ct", "c"), builder.literal(0)),
falseLiteral);
}
break;
}
if (!keyIsNulls.isEmpty()) {
operands.add(builder.or(keyIsNulls), unknownLiteral);
}
if (allLiterals) {
operands.add(builder.isNotNull(builder.field("cs")),
trueLiteral);
} else {
operands.add(builder.isNotNull(Util.last(builder.fields())),
trueLiteral);
}
if (!allLiterals) {
switch (logic) {
case TRUE_FALSE_UNKNOWN:
case UNKNOWN_AS_TRUE:
operands.add(
builder.call(SqlStdOperatorTable.LESS_THAN,
builder.field("ct", "ck"), builder.field("ct", "c")),
b);
}
}
operands.add(falseLiteral);
return builder.call(SqlStdOperatorTable.CASE, operands.build());
}
/** Returns a reference to a particular field, by offset, across several
* inputs on a {@link RelBuilder}'s stack. */
private RexInputRef field(RelBuilder builder, int inputCount, int offset) {
for (int inputOrdinal = 0;;) {
final RelNode r = builder.peek(inputCount, inputOrdinal);
if (offset < r.getRowType().getFieldCount()) {
return builder.field(inputCount, inputOrdinal, offset);
}
++inputOrdinal;
offset -= r.getRowType().getFieldCount();
}
}
/** Returns a list of expressions that project the first {@code fieldCount}
* fields of the top input on a {@link RelBuilder}'s stack. */
private static List fields(RelBuilder builder, int fieldCount) {
final List projects = new ArrayList<>();
for (int i = 0; i < fieldCount; i++) {
projects.add(builder.field(i));
}
return projects;
}
/** Rule that converts sub-queries from project expressions into
* {@link Correlate} instances. */
public static class SubQueryProjectRemoveRule extends SubQueryRemoveRule {
public SubQueryProjectRemoveRule(RelBuilderFactory relBuilderFactory) {
super(
operandJ(Project.class, null,
RexUtil.SubQueryFinder::containsSubQuery, any()),
relBuilderFactory, "SubQueryRemoveRule:Project");
}
public void onMatch(RelOptRuleCall call) {
final Project project = call.rel(0);
final RelBuilder builder = call.builder();
final RexSubQuery e =
RexUtil.SubQueryFinder.find(project.getProjects());
assert e != null;
final RelOptUtil.Logic logic =
LogicVisitor.find(RelOptUtil.Logic.TRUE_FALSE_UNKNOWN,
project.getProjects(), e);
builder.push(project.getInput());
final int fieldCount = builder.peek().getRowType().getFieldCount();
final Set variablesSet =
RelOptUtil.getVariablesUsed(e.rel);
final RexNode target = apply(e, variablesSet,
logic, builder, 1, fieldCount);
final RexShuttle shuttle = new ReplaceSubQueryShuttle(e, target);
builder.project(shuttle.apply(project.getProjects()),
project.getRowType().getFieldNames());
call.transformTo(builder.build());
}
}
/** Rule that converts a sub-queries from filter expressions into
* {@link Correlate} instances. */
public static class SubQueryFilterRemoveRule extends SubQueryRemoveRule {
public SubQueryFilterRemoveRule(RelBuilderFactory relBuilderFactory) {
super(
operandJ(Filter.class, null, RexUtil.SubQueryFinder::containsSubQuery,
any()), relBuilderFactory, "SubQueryRemoveRule:Filter");
}
public void onMatch(RelOptRuleCall call) {
final Filter filter = call.rel(0);
final RelBuilder builder = call.builder();
builder.push(filter.getInput());
int count = 0;
RexNode c = filter.getCondition();
while (true) {
final RexSubQuery e = RexUtil.SubQueryFinder.find(c);
if (e == null) {
assert count > 0;
break;
}
++count;
final RelOptUtil.Logic logic =
LogicVisitor.find(RelOptUtil.Logic.TRUE, ImmutableList.of(c), e);
final Set variablesSet =
RelOptUtil.getVariablesUsed(e.rel);
final RexNode target = apply(e, variablesSet, logic,
builder, 1, builder.peek().getRowType().getFieldCount());
final RexShuttle shuttle = new ReplaceSubQueryShuttle(e, target);
c = c.accept(shuttle);
}
builder.filter(c);
builder.project(fields(builder, filter.getRowType().getFieldCount()));
call.transformTo(builder.build());
}
}
/** Rule that converts sub-queries from join expressions into
* {@link Correlate} instances. */
public static class SubQueryJoinRemoveRule extends SubQueryRemoveRule {
public SubQueryJoinRemoveRule(RelBuilderFactory relBuilderFactory) {
super(
operandJ(Join.class, null, RexUtil.SubQueryFinder::containsSubQuery,
any()), relBuilderFactory, "SubQueryRemoveRule:Join");
}
public void onMatch(RelOptRuleCall call) {
final Join join = call.rel(0);
final RelBuilder builder = call.builder();
final RexSubQuery e =
RexUtil.SubQueryFinder.find(join.getCondition());
assert e != null;
final RelOptUtil.Logic logic =
LogicVisitor.find(RelOptUtil.Logic.TRUE,
ImmutableList.of(join.getCondition()), e);
builder.push(join.getLeft());
builder.push(join.getRight());
final int fieldCount = join.getRowType().getFieldCount();
final Set variablesSet =
RelOptUtil.getVariablesUsed(e.rel);
final RexNode target = apply(e, variablesSet,
logic, builder, 2, fieldCount);
final RexShuttle shuttle = new ReplaceSubQueryShuttle(e, target);
builder.join(join.getJoinType(), shuttle.apply(join.getCondition()));
builder.project(fields(builder, join.getRowType().getFieldCount()));
call.transformTo(builder.build());
}
}
/** Shuttle that replaces occurrences of a given
* {@link com.hazelcast.org.apache.calcite.rex.RexSubQuery} with a replacement
* expression. */
private static class ReplaceSubQueryShuttle extends RexShuttle {
private final RexSubQuery subQuery;
private final RexNode replacement;
ReplaceSubQueryShuttle(RexSubQuery subQuery, RexNode replacement) {
this.subQuery = subQuery;
this.replacement = replacement;
}
@Override public RexNode visitSubQuery(RexSubQuery subQuery) {
return subQuery.equals(this.subQuery) ? replacement : subQuery;
}
}
}