kgyrtkirk commented on a change in pull request #1322: [CALCITE-3198]
ReduceExpressionsRule.FILTER_INSTANCE does not reduce 'NOT(x=a AND x=b)'
URL: https://github.com/apache/calcite/pull/1322#discussion_r305635221
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File path: core/src/main/java/org/apache/calcite/rex/RexSimplify.java
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@@ -1624,6 +1626,24 @@ private RexNode simplifyOrs(List<RexNode> terms,
RexUnknownAs unknownAs) {
continue;
}
}
+ break;
+ case NOT_EQUALS:
+ Comparison notEqualsComparison =
+ Comparison.of(term, node -> RexUtil.isReferenceOrAccess(node,
false));
+ if (notEqualsComparison != null) {
+ Comparison prevNotEqualsComparison =
notEqualsComparisonMap.get(notEqualsComparison.ref);
+ if (prevNotEqualsComparison == null) {
+ notEqualsComparisonMap.put(notEqualsComparison.ref,
notEqualsComparison);
+ } else {
+ Comparable comparable1 = notEqualsComparison.literal.getValue();
+ Comparable comparable2 =
prevNotEqualsComparison.literal.getValue();
+ //noinspection unchecked
+ if (comparable1.compareTo(comparable2) != 0) {
+ return rexBuilder.makeLiteral(true);
Review comment:
what if `x != 0 || x!= 1` in case x is a nullable variable?
when `x is null`; I think the expression should evaluate to `null` instead
of `true`
I'm not sure if this is right now in a specific unknownas mode (doesn't
seems so); or the operands are non nullables - but the best is to assume that
operand of the comparision might be nullable without even considering the
actual unknownAs mode.
the important thing is that I think at this point you may only conclude that
`x is not null or null`
Which is `true` in some cases:
* like when `x is of a type which is not nullable`
* or in unknownas.TRUE mode
you may narrow down this to match only the known good ones; or use the above
generalized fact and let other parts of reximplify to do the rest
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