Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/686#discussion_r92290434
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/SizedJBlock.java ---
@@ -32,7 +32,11 @@
public SizedJBlock(JBlock block) {
this.block = block;
- this.count = 0;
+ // count should be 1 because in some cases it is hard to increase it
when
+ // Logical Expressions are added to JBlock.
+ // To avoid taking into account of some extra count from empty JBlock,
--- End diff --
I spent some time to understand why modifying this count makes the query
compilation works.
The failing case encounter compilation failure in Copier (for SVR
operator). Turns out that the idea of SizedJBlock (DRILL-4715) only works when
we call ClassGenerator.addExpr(). This is fine with Project, Filter,
Aggregator, etc, but not for Copier. The Copier is doing kind of short-cut
handling, by accessing the eval() and setup() directly [1].
Ideally, we probably should try to see if we can convert Copier using same
mechanism in Project/Filter. After some thoughts, I realized doing that might
add additional overhead, as the current way is doing the copying directly.
Given that, I'm fine with this proposed change. Please add comments to
explain why we set count = 1.
[1]
https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/vector/CopyUtil.java#L45-L50
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