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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed 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 com.google.devtools.build.lib.query2.engine;
import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListeningExecutorService;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.devtools.build.lib.query2.engine.Lexer.TokenKind;
import com.google.devtools.build.lib.util.Preconditions;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.atomic.AtomicReference;
/**
* A binary algebraic set operation.
*
* <pre>
* expr ::= expr (INTERSECT expr)+
* | expr ('^' expr)+
* | expr (UNION expr)+
* | expr ('+' expr)+
* | expr (EXCEPT expr)+
* | expr ('-' expr)+
* </pre>
*/
public class BinaryOperatorExpression extends QueryExpression {
private final Lexer.TokenKind operator; // ::= INTERSECT/CARET | UNION/PLUS | EXCEPT/MINUS
private final ImmutableList<QueryExpression> operands;
BinaryOperatorExpression(Lexer.TokenKind operator,
List<QueryExpression> operands) {
Preconditions.checkState(operands.size() > 1);
this.operator = operator;
this.operands = ImmutableList.copyOf(operands);
}
Lexer.TokenKind getOperator() {
return operator;
}
public ImmutableList<QueryExpression> getOperands() {
return operands;
}
@Override
public <T> void eval(QueryEnvironment<T> env, Callback<T> callback)
throws QueryException, InterruptedException {
evalConcurrently(env, callback, MoreExecutors.newDirectExecutorService());
}
@Override
public <T> void evalConcurrently(
final QueryEnvironment<T> env,
final Callback<T> callback,
ListeningExecutorService executorService)
throws QueryException, InterruptedException {
if (operator == TokenKind.PLUS || operator == TokenKind.UNION) {
final AtomicReference<InterruptedException> interruptRef = new AtomicReference<>();
final AtomicReference<QueryException> queryExceptionRef = new AtomicReference<>();
ArrayList<ListenableFuture<?>> futures = new ArrayList<>(operands.size());
for (final QueryExpression operand : operands) {
// When executorService has an implementation that evaluates runnables in a non-serial
// order, like a fixedSizeThreadPool, the following code does not guarantee that operands'
// targets are emitted via the callback in the operands' order. And that's OK!
// BinaryOperatorExpression is a set operation. The query documentation states
// that set operations don't introduce any ordering constraints of their own.
//
// Ordering constraints for other kinds of expressions are enforced by the query
// environment.
futures.add(
executorService.submit(
new Runnable() {
@Override
public void run() {
try {
env.eval(operand, callback);
} catch (QueryException e) {
queryExceptionRef.compareAndSet(null, e);
} catch (InterruptedException e) {
interruptRef.compareAndSet(null, e);
}
}
}));
}
try {
Futures.allAsList(futures).get();
} catch (ExecutionException e) {
throw new IllegalStateException(e);
}
InterruptedException interruptedExceptionIfAny = interruptRef.get();
if (interruptedExceptionIfAny != null) {
throw interruptedExceptionIfAny;
}
QueryException queryException = queryExceptionRef.get();
if (queryException != null) {
throw queryException;
}
return;
}
// We cannot do differences with partial results. So we fully evaluate the operands
Set<T> lhsValue = QueryUtil.evalAll(env, operands.get(0));
for (int i = 1; i < operands.size(); i++) {
Set<T> rhsValue = QueryUtil.evalAll(env, operands.get(i));
switch (operator) {
case INTERSECT:
case CARET:
lhsValue.retainAll(rhsValue);
break;
case EXCEPT:
case MINUS:
lhsValue.removeAll(rhsValue);
break;
case UNION:
case PLUS:
default:
throw new IllegalStateException("operator=" + operator);
}
}
callback.process(lhsValue);
}
@Override
public void collectTargetPatterns(Collection<String> literals) {
for (QueryExpression subExpression : operands) {
subExpression.collectTargetPatterns(literals);
}
}
@Override
public QueryExpression getMapped(QueryExpressionMapper mapper) {
return mapper.map(this);
}
@Override
public String toString() {
StringBuilder result = new StringBuilder();
for (int i = 1; i < operands.size(); i++) {
result.append("(");
}
result.append(operands.get(0));
for (int i = 1; i < operands.size(); i++) {
result.append(" " + operator.getPrettyName() + " " + operands.get(i) + ")");
}
return result.toString();
}
}
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