Github user JamesRTaylor commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/208#discussion_r78280999
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/compile/ExpressionCompiler.java
---
@@ -523,7 +523,12 @@ public Expression visitLeave(LikeParseNode node,
List<Expression> children) thro
byte[] wildcard = {StringUtil.MULTI_CHAR_LIKE};
StringUtil.fill(nullExpressionString, 0, pattern.length(),
wildcard, 0, 1, false);
if (pattern.equals(new String (nullExpressionString))) {
- return IsNullExpression.create(lhs, true,
context.getTempPtr());
--- End diff --
I think the original code, optimizing to COL IS NOT NULL is not correct,
because if COL is null, it'll evaluate to false when it should evaluate to
null. Instead, I think it should become COL >= CAST(KeyRange.IS_NOT_NULL_RANGE
AS VARCHAR) and for the negate case, it'd be COL <
CAST(KeyRange.IS_NOT_NULL_RANGE AS VARCHAR). That way in any case, if COL is
null, the expression will evaluate to null. If COL is any string then the first
expression will evaluate to true and the latter to false.
The code will look something like this:
// Declare this as a static constant at top of file
private static final Expression NOT_NULL_STRING =
LiteralExpression.newConstant(PVarchar.INSTANCE.toObject(KeyRange.IS_NOT_NULL_RANGE.getLowerRange()));
List<Expression> compareChildren = Arrays.asList(lhs, NOT_NULL_STRING);
return new ComparisonExpression.create(compareChildren, node.isNegate()
? CompareOp.LESS : CompareOp.GREATER_OR_EQUAL);
Then make sure we have tests around COL being null too.
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