Leonard Xu created CALCITE-3368:
-----------------------------------
Summary: Nonequivalent simplification happens in RexSimplify
Key: CALCITE-3368
URL: https://issues.apache.org/jira/browse/CALCITE-3368
Project: Calcite
Issue Type: Bug
Components: core
Affects Versions: 1.21.0
Reporter: Leonard Xu
Fix For: 1.22.0
When I do some overflow test ，I found that Calcite's simplification logic of
isNull expression will convert from
*"f(operand0, operand1) IS NULL"* to
*"operand0 IS NULL OR operand1 IS NULL"* if the Policy of RexNode‘s SqlKind
is ANY 。
This simplification will not calculate the real vale of *f(operand0,
operand1)* (eg..'f0 + 'f1 ）which maybe overflow.
{code:java}
//org.apache.calcite.rex.RexSimplify.java
private RexNode simplifyIsNull(RexNode a) {
// Simplify the argument first,
// call ourselves recursively to see whether we can make more progress.
// For example, given
// "(CASE WHEN FALSE THEN 1 ELSE 2) IS NULL" we first simplify the
// argument to "2", and only then we can simplify "2 IS NULL" to "FALSE".
a = simplify(a, UNKNOWN);
if (!a.getType().isNullable() && isSafeExpression(a)) {
return rexBuilder.makeLiteral(false);
}
if (RexUtil.isNull(a)) {
return rexBuilder.makeLiteral(true);
}
if (a.getKind() == SqlKind.CAST) {
return null;
}
switch (Strong.policy(a.getKind())) {
case NOT_NULL:
return rexBuilder.makeLiteral(false);
case ANY:
// "f" is a strong operator, so "f(operand0, operand1) IS NULL" simplifies
// to "operand0 IS NULL OR operand1 IS NULL"
final List<RexNode> operands = new ArrayList<>();
for (RexNode operand : ((RexCall) a).getOperands()) {
final RexNode simplified = simplifyIsNull(operand);
if (simplified == null) {
operands.add(
rexBuilder.makeCall(SqlStdOperatorTable.IS_NULL, operand));
} else {
operands.add(simplified);
}
}
return RexUtil.composeDisjunction(rexBuilder, operands, false);
case AS_IS:
default:
return null;
}
}{code}
And most of calculating SqlKinds are assigned *Policy.ANY* at present.
{code:java}
//org.apache.calcite.plan.Strong.java
public static Policy policy(SqlKind kind) {
return MAP.getOrDefault(kind, Policy.AS_IS);
}
....
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);
* 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,
}{code}
It should be an obvious nonequivalent simplification.
And this issue come from Flink
（[FLINK-14030|https://issues.apache.org/jira/browse/FLINK-14030]）.
[~danny0405] could you have a look at this?
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
