Thomas Nielsen wrote:
A B (JIRA) wrote:
I think the condition may need to be narrowed down even further: EXISTS
subqueries _are_ allowed to be flattened from a WHERE clause _if_ that
subquery's WHERE clause does not itself contain another subquery.
Correct - the updated patch I'm working on attempts to skip flattening
only in this scenario as per the javadoc in derby-3301-1.diff, and still
flatten EXISTS subqueries without a subquery in the where clause.
Okay, great. I didn't quite get that from the first version of the
patch/comments. Thanks for clarifying.
If at all possible, I think it'd be better to fix the flattening
condition for the specific situation of nested subqueries than
to completely disable WHERE clause flattening for EXISTS subqueries.
That is the intent of the upcoming patch.
Ok, this sounds good :)
I shared your fear, but suites.All actually ran cleanly with the patch
applied.
What about derbyall? My guess is that most tests which verify query
plans currently reside in derbyall as they have not yet been converted
to JUnit. If there are no tests to explicitly check for the occurrence
of EXISTS subquery flattening, then that seems like an oversight in the
testing for such flattening...but that would be a separate issue
altogether (not something you'd have to address for DERBY-3301).
Army
