/*
* 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.split;
import com.facebook.presto.spi.ConnectorColumnHandle;
import com.facebook.presto.sql.planner.Symbol;
import com.facebook.presto.sql.tree.BooleanLiteral;
import com.facebook.presto.sql.tree.ComparisonExpression;
import com.facebook.presto.sql.tree.DoubleLiteral;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.sql.tree.Literal;
import com.facebook.presto.sql.tree.LongLiteral;
import com.facebook.presto.sql.tree.QualifiedNameReference;
import com.facebook.presto.sql.tree.StringLiteral;
import com.facebook.presto.util.IterableTransformer;
import com.google.common.base.Optional;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import static com.facebook.presto.sql.ExpressionUtils.extractConjuncts;
import static com.facebook.presto.sql.tree.ComparisonExpression.matchesPattern;
import static com.google.common.base.Predicates.instanceOf;
import static com.google.common.base.Predicates.or;
public final class ExpressionUtil
{
private ExpressionUtil()
{
}
/**
* Extract constant values from expression.
*
* @return the constant values or absent if expression will always be false
*/
public static Optional<Map<ConnectorColumnHandle, Object>> extractConstantValues(Expression predicate, Map<Symbol, ConnectorColumnHandle> symbolToColumnName)
{
// Look for any sub-expression in an AND expression of the form <partition key> = 'value'
Set<ComparisonExpression> comparisons = IterableTransformer.on(extractConjuncts(predicate))
.select(instanceOf(ComparisonExpression.class))
.cast(ComparisonExpression.class)
.select(or(
matchesPattern(ComparisonExpression.Type.EQUAL, QualifiedNameReference.class, StringLiteral.class),
matchesPattern(ComparisonExpression.Type.EQUAL, StringLiteral.class, QualifiedNameReference.class),
matchesPattern(ComparisonExpression.Type.EQUAL, QualifiedNameReference.class, LongLiteral.class),
matchesPattern(ComparisonExpression.Type.EQUAL, LongLiteral.class, QualifiedNameReference.class),
matchesPattern(ComparisonExpression.Type.EQUAL, QualifiedNameReference.class, DoubleLiteral.class),
matchesPattern(ComparisonExpression.Type.EQUAL, DoubleLiteral.class, QualifiedNameReference.class),
matchesPattern(ComparisonExpression.Type.EQUAL, QualifiedNameReference.class, BooleanLiteral.class),
matchesPattern(ComparisonExpression.Type.EQUAL, BooleanLiteral.class, QualifiedNameReference.class)))
.set();
final Map<ConnectorColumnHandle, Object> bindings = new HashMap<>();
for (ComparisonExpression comparison : comparisons) {
// Record binding if condition is an equality comparison over a partition key
QualifiedNameReference reference = extractReference(comparison);
Symbol symbol = Symbol.fromQualifiedName(reference.getName());
ConnectorColumnHandle column = symbolToColumnName.get(symbol);
if (column != null) {
Literal literal = extractLiteral(comparison);
Object value;
if (literal instanceof DoubleLiteral) {
value = ((DoubleLiteral) literal).getValue();
}
else if (literal instanceof LongLiteral) {
value = ((LongLiteral) literal).getValue();
}
else if (literal instanceof StringLiteral) {
value = ((StringLiteral) literal).getValue();
}
else if (literal instanceof BooleanLiteral) {
value = ((BooleanLiteral) literal).getValue();
}
else {
throw new AssertionError(String.format("Literal type (%s) not currently handled", literal.getClass().getName()));
}
// if there is a different constant value already bound for this column, the expression will always be false
Object previous = bindings.get(column);
if (previous != null && !previous.equals(value)) {
return Optional.absent();
}
bindings.put(column, value);
}
}
return Optional.of(bindings);
}
private static Literal extractLiteral(ComparisonExpression expression)
{
if (expression.getLeft() instanceof Literal) {
return (Literal) expression.getLeft();
}
else if (expression.getRight() instanceof Literal) {
return (Literal) expression.getRight();
}
throw new IllegalArgumentException("Comparison does not have a child of type Literal");
}
private static QualifiedNameReference extractReference(ComparisonExpression expression)
{
if (expression.getLeft() instanceof QualifiedNameReference) {
return (QualifiedNameReference) expression.getLeft();
}
else if (expression.getRight() instanceof QualifiedNameReference) {
return (QualifiedNameReference) expression.getRight();
}
throw new IllegalArgumentException("Comparison does not have a child of type QualifiedNameReference");
}
}