org.apache.calcite.plan.Strong Maven / Gradle / Ivy
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/*
* 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 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 org.apache.calcite.plan;
import org.apache.calcite.rex.RexCall;
import org.apache.calcite.rex.RexInputRef;
import org.apache.calcite.rex.RexLiteral;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.rex.RexUtil;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.util.ImmutableBitSet;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import java.util.ArrayList;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
/** Utilities for strong predicates.
*
* A predicate is strong (or null-rejecting) if it is UNKNOWN if any of its
* inputs is UNKNOWN.
*
* By the way, UNKNOWN is just the boolean form of NULL.
*
* Examples:
*
* - {@code UNKNOWN} is strong in [] (definitely null)
*
- {@code c = 1} is strong in [c] (definitely null if and only if c is
* null)
*
- {@code c IS NULL} is not strong (always returns TRUE or FALSE, never
* null)
*
- {@code p1 AND p2} is strong in [p1, p2] (definitely null if either p1
* is null or p2 is null)
*
- {@code p1 OR p2} is strong if p1 and p2 are strong
*
- {@code c1 = 1 OR c2 IS NULL} is strong in [c1] (definitely null if c1
* is null)
*
*/
public class Strong {
private static final Map MAP = createPolicyMap();
public Strong() {
super();
}
/** Returns a checker that consults a bit set to find out whether particular
* inputs may be null. */
public static Strong of(final ImmutableBitSet nullColumns) {
return new Strong() {
@Override public boolean isNull(RexInputRef ref) {
return nullColumns.get(ref.getIndex());
}
};
}
/** Returns whether the analyzed expression will definitely return null if
* all of a given set of input columns are null. */
public static boolean isNull(RexNode node, ImmutableBitSet nullColumns) {
return of(nullColumns).isNull(node);
}
/** Returns whether the analyzed expression will definitely not return true
* (equivalently, will definitely not return null or false) if
* all of a given set of input columns are null. */
public static boolean isNotTrue(RexNode node, ImmutableBitSet nullColumns) {
return of(nullColumns).isNotTrue(node);
}
/** Returns how to deduce whether a particular kind of expression is null,
* given whether its arguments are null. */
public static Policy policy(SqlKind kind) {
return Objects.requireNonNull(MAP.get(kind), kind.toString());
}
/** Returns whether an expression is definitely not true. */
public boolean isNotTrue(RexNode node) {
switch (node.getKind()) {
case IS_NOT_NULL:
return anyNull(((RexCall) node).getOperands());
default:
return isNull(node);
}
}
/** Returns whether an expression is definitely null.
*
* The answer is based on calls to {@link #isNull} for its constituent
* expressions, and you may override methods to test hypotheses such as
* "if {@code x} is null, is {@code x + y} null? */
public boolean isNull(RexNode node) {
final Policy policy = MAP.get(node.getKind());
switch (policy) {
case NOT_NULL:
return false;
case ANY:
return anyNull(((RexCall) node).getOperands());
default:
break;
}
switch (node.getKind()) {
case LITERAL:
return ((RexLiteral) node).isNull();
// We can only guarantee AND to return NULL if both inputs are NULL (similar for OR)
// AND(NULL, FALSE) = FALSE
case AND:
case OR:
case COALESCE:
return allNull(((RexCall) node).getOperands());
case NULLIF:
// NULLIF(null, X) where X can be NULL, returns NULL
// NULLIF(X, Y) where X is not NULL, then this may return NULL if X = Y, otherwise X.
return allNull(ImmutableList.of(((RexCall) node).getOperands().get(0)));
case INPUT_REF:
return isNull((RexInputRef) node);
case CASE:
final RexCall caseCall = (RexCall) node;
final List caseValues = new ArrayList<>();
for (int i = 0; i < caseCall.getOperands().size(); i++) {
if (!RexUtil.isCasePredicate(caseCall, i)) {
caseValues.add(caseCall.getOperands().get(i));
}
}
return allNull(caseValues);
default:
return false;
}
}
/** Returns whether a given input is definitely null. */
public boolean isNull(RexInputRef ref) {
return false;
}
/** Returns whether all expressions in a list are definitely null. */
private boolean allNull(List operands) {
for (RexNode operand : operands) {
if (!isNull(operand)) {
return false;
}
}
return true;
}
/** Returns whether any expressions in a list are definitely null. */
private boolean anyNull(List operands) {
for (RexNode operand : operands) {
if (isNull(operand)) {
return true;
}
}
return false;
}
private static Map createPolicyMap() {
EnumMap map = new EnumMap<>(SqlKind.class);
map.put(SqlKind.INPUT_REF, Policy.AS_IS);
map.put(SqlKind.LOCAL_REF, Policy.AS_IS);
map.put(SqlKind.DYNAMIC_PARAM, Policy.AS_IS);
map.put(SqlKind.OTHER_FUNCTION, Policy.AS_IS);
// The following types of expressions could potentially be custom.
map.put(SqlKind.CASE, Policy.AS_IS);
// CAST('abc' as int) yields NULL, but CAST('1' as int) yields 1
map.put(SqlKind.CAST, Policy.AS_IS);
map.put(SqlKind.DECODE, Policy.AS_IS);
// NULLIF(1, NULL) yields 1, but NULLIF(1, 1) yields NULL
map.put(SqlKind.NULLIF, Policy.AS_IS);
// COALESCE(NULL, 2) yields 2
map.put(SqlKind.COALESCE, Policy.AS_IS);
map.put(SqlKind.NVL, Policy.AS_IS);
// FALSE AND NULL yields FALSE
// TRUE AND NULL yields NULL
map.put(SqlKind.AND, Policy.AS_IS);
// TRUE OR NULL yields TRUE
// FALSE OR NULL yields NULL
map.put(SqlKind.OR, Policy.AS_IS);
// Expression types with custom handlers.
map.put(SqlKind.LITERAL, Policy.CUSTOM);
map.put(SqlKind.EXISTS, Policy.NOT_NULL);
map.put(SqlKind.IS_DISTINCT_FROM, Policy.NOT_NULL);
map.put(SqlKind.IS_NOT_DISTINCT_FROM, Policy.NOT_NULL);
map.put(SqlKind.IS_NULL, Policy.NOT_NULL);
map.put(SqlKind.IS_NOT_NULL, Policy.NOT_NULL);
map.put(SqlKind.IS_TRUE, Policy.NOT_NULL);
map.put(SqlKind.IS_NOT_TRUE, Policy.NOT_NULL);
map.put(SqlKind.IS_FALSE, Policy.NOT_NULL);
map.put(SqlKind.IS_NOT_FALSE, Policy.NOT_NULL);
map.put(SqlKind.IS_DISTINCT_FROM, Policy.NOT_NULL);
map.put(SqlKind.IS_NOT_DISTINCT_FROM, Policy.NOT_NULL);
map.put(SqlKind.NOT, Policy.ANY);
map.put(SqlKind.EQUALS, Policy.ANY);
map.put(SqlKind.NOT_EQUALS, Policy.ANY);
map.put(SqlKind.LESS_THAN, Policy.ANY);
map.put(SqlKind.LESS_THAN_OR_EQUAL, Policy.ANY);
map.put(SqlKind.GREATER_THAN, Policy.ANY);
map.put(SqlKind.GREATER_THAN_OR_EQUAL, Policy.ANY);
map.put(SqlKind.LIKE, Policy.ANY);
map.put(SqlKind.SIMILAR, Policy.ANY);
map.put(SqlKind.PLUS_PREFIX, Policy.ANY);
map.put(SqlKind.MINUS_PREFIX, Policy.ANY);
map.put(SqlKind.PLUS, Policy.ANY);
map.put(SqlKind.PLUS_PREFIX, Policy.ANY);
map.put(SqlKind.MINUS, Policy.ANY);
map.put(SqlKind.MINUS_PREFIX, Policy.ANY);
map.put(SqlKind.TIMES, Policy.ANY);
map.put(SqlKind.DIVIDE, Policy.ANY);
map.put(SqlKind.REINTERPRET, Policy.ANY);
map.put(SqlKind.TRIM, Policy.ANY);
map.put(SqlKind.LTRIM, Policy.ANY);
map.put(SqlKind.RTRIM, Policy.ANY);
map.put(SqlKind.CEIL, Policy.ANY);
map.put(SqlKind.FLOOR, Policy.ANY);
map.put(SqlKind.EXTRACT, Policy.ANY);
map.put(SqlKind.GREATEST, Policy.ANY);
map.put(SqlKind.LEAST, Policy.ANY);
map.put(SqlKind.TIMESTAMP_ADD, Policy.ANY);
map.put(SqlKind.TIMESTAMP_DIFF, Policy.ANY);
// Assume that any other expressions cannot be simplified.
for (SqlKind k
: Iterables.concat(SqlKind.EXPRESSION, SqlKind.AGGREGATE)) {
if (!map.containsKey(k)) {
map.put(k, Policy.AS_IS);
}
}
return map;
}
/** How whether an operator's operands are null affects whether a call to
* that operator evaluates to null. */
public enum Policy {
/** This kind of expression is never null. No need to look at its arguments,
* if it has any. */
NOT_NULL,
/** This kind of expression has its own particular rules about whether it
* is null. */
CUSTOM,
/** This kind of expression is null if and only if at least one of its
* arguments is null. */
ANY,
/** This kind of expression may be null. There is no way to rewrite. */
AS_IS,
}
}
// End Strong.java