/*
* 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.facebook.presto.sql.planner.optimizations;
import com.facebook.presto.metadata.Metadata;
import com.facebook.presto.spi.ConnectorSession;
import com.facebook.presto.sql.planner.ExpressionInterpreter;
import com.facebook.presto.sql.planner.LiteralInterpreter;
import com.facebook.presto.sql.planner.NoOpSymbolResolver;
import com.facebook.presto.sql.planner.PlanNodeIdAllocator;
import com.facebook.presto.sql.planner.Symbol;
import com.facebook.presto.sql.planner.SymbolAllocator;
import com.facebook.presto.sql.planner.plan.FilterNode;
import com.facebook.presto.sql.planner.plan.PlanNode;
import com.facebook.presto.sql.planner.plan.PlanNodeRewriter;
import com.facebook.presto.sql.planner.plan.PlanRewriter;
import com.facebook.presto.sql.planner.plan.ProjectNode;
import com.facebook.presto.sql.planner.plan.TableScanNode;
import com.facebook.presto.sql.tree.BooleanLiteral;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.spi.type.Type;
import com.google.common.base.Function;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import java.util.IdentityHashMap;
import java.util.Map;
import static com.facebook.presto.sql.analyzer.ExpressionAnalyzer.getExpressionTypes;
import static com.google.common.base.Preconditions.checkNotNull;
public class SimplifyExpressions
extends PlanOptimizer
{
private final Metadata metadata;
public SimplifyExpressions(Metadata metadata)
{
this.metadata = checkNotNull(metadata, "metadata is null");
}
@Override
public PlanNode optimize(PlanNode plan, ConnectorSession session, Map<Symbol, Type> types, SymbolAllocator symbolAllocator, PlanNodeIdAllocator idAllocator)
{
checkNotNull(plan, "plan is null");
checkNotNull(session, "session is null");
checkNotNull(types, "types is null");
checkNotNull(symbolAllocator, "symbolAllocator is null");
checkNotNull(idAllocator, "idAllocator is null");
return PlanRewriter.rewriteWith(new Rewriter(metadata, session, types), plan);
}
private static class Rewriter
extends PlanNodeRewriter<Void>
{
private final Metadata metadata;
private final ConnectorSession session;
private final Map<Symbol, Type> types;
public Rewriter(Metadata metadata, ConnectorSession session, Map<Symbol, Type> types)
{
this.metadata = metadata;
this.session = session;
this.types = types;
}
@Override
public PlanNode rewriteProject(ProjectNode node, Void context, PlanRewriter<Void> planRewriter)
{
PlanNode source = planRewriter.rewrite(node.getSource(), context);
Map<Symbol, Expression> assignments = ImmutableMap.copyOf(Maps.transformValues(node.getOutputMap(), simplifyExpressionFunction()));
return new ProjectNode(node.getId(), source, assignments);
}
@Override
public PlanNode rewriteFilter(FilterNode node, Void context, PlanRewriter<Void> planRewriter)
{
PlanNode source = planRewriter.rewrite(node.getSource(), context);
Expression simplified = simplifyExpression(node.getPredicate());
if (simplified.equals(BooleanLiteral.TRUE_LITERAL)) {
return source;
}
return new FilterNode(node.getId(), source, simplified);
}
@Override
public PlanNode rewriteTableScan(TableScanNode node, Void context, PlanRewriter<Void> planRewriter)
{
Expression originalConstraint = null;
if (node.getOriginalConstraint() != null) {
originalConstraint = simplifyExpression(node.getOriginalConstraint());
}
return new TableScanNode(node.getId(), node.getTable(), node.getOutputSymbols(), node.getAssignments(), originalConstraint, node.getSummarizedPartition());
}
private Function<Expression, Expression> simplifyExpressionFunction()
{
return new Function<Expression, Expression>()
{
@Override
public Expression apply(Expression input)
{
return simplifyExpression(input);
}
};
}
private Expression simplifyExpression(Expression input)
{
IdentityHashMap<Expression, Type> expressionTypes = getExpressionTypes(session, metadata, types, input);
ExpressionInterpreter interpreter = ExpressionInterpreter.expressionOptimizer(input, metadata, session, expressionTypes);
return LiteralInterpreter.toExpression(interpreter.optimize(NoOpSymbolResolver.INSTANCE), expressionTypes.get(input));
}
}
}