/*
* 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.gen;
import com.facebook.presto.byteCode.Block;
import com.facebook.presto.byteCode.ByteCodeNode;
import com.facebook.presto.byteCode.CompilerContext;
import com.facebook.presto.byteCode.control.IfStatement;
import com.facebook.presto.byteCode.instruction.LabelNode;
import com.facebook.presto.metadata.FunctionInfo;
import com.facebook.presto.metadata.FunctionRegistry;
import com.facebook.presto.metadata.OperatorType;
import com.facebook.presto.metadata.Signature;
import com.facebook.presto.spi.type.Type;
import com.facebook.presto.sql.relational.RowExpression;
import com.google.common.collect.ImmutableList;
import java.util.List;
public class NullIfCodeGenerator
implements ByteCodeGenerator
{
@Override
public ByteCodeNode generateExpression(Signature signature, ByteCodeGeneratorContext generatorContext, Type returnType, List<RowExpression> arguments)
{
CompilerContext context = generatorContext.getContext();
RowExpression first = arguments.get(0);
RowExpression second = arguments.get(1);
LabelNode notMatch = new LabelNode("notMatch");
// push first arg on the stack
Block block = new Block(context)
.comment("check if first arg is null")
.append(generatorContext.generate(first))
.append(ByteCodeUtils.ifWasNullPopAndGoto(context, notMatch, void.class));
Type firstType = first.getType();
Type secondType = second.getType();
// this is a hack! We shouldn't be determining type coercions at this point, but there's no way
// around it in the current expression AST
Type commonType = FunctionRegistry.getCommonSuperType(firstType, secondType).get();
// if (equal(cast(first as <common type>), cast(second as <common type>))
FunctionInfo equalsFunction = generatorContext.getRegistry().resolveOperator(OperatorType.EQUAL, ImmutableList.of(firstType, secondType));
ByteCodeNode equalsCall = generatorContext.generateCall(
equalsFunction,
ImmutableList.of(
cast(generatorContext, new Block(context).dup(firstType.getJavaType()), firstType, commonType),
cast(generatorContext, generatorContext.generate(second), secondType, commonType)));
Block conditionBlock = new Block(context)
.append(equalsCall)
.append(ByteCodeUtils.ifWasNullClearPopAndGoto(context, notMatch, void.class, boolean.class));
// if first and second are equal, return null
Block trueBlock = new Block(context)
.putVariable("wasNull", true)
.pop(first.getType().getJavaType())
.pushJavaDefault(first.getType().getJavaType());
// else return first (which is still on the stack
block.append(new IfStatement(context, conditionBlock, trueBlock, notMatch));
return block;
}
private ByteCodeNode cast(ByteCodeGeneratorContext generatorContext, ByteCodeNode argument, Type fromType, Type toType)
{
FunctionInfo function = generatorContext
.getRegistry()
.getCoercion(fromType, toType);
// TODO: do we need a full function call? (nullability checks, etc)
return generatorContext.generateCall(function, ImmutableList.of(argument));
}
}