[ http://issues.apache.org/jira/browse/DERBY-1866?page=all ]
A B updated DERBY-1866:
-----------------------
Attachment: d1866_v1.patch
Attaching a first patch for this issue, d1866_v1.patch. In short, the problem
was that, when pushing predicates to subqueries beneath UNIONs, the predicates
were always being pushed to the *first* table in the subquery's FROM list,
regardless of whether or not that was actually the correct table. Thus it was
possible to push a predicate down to a base table to which it didn't apply,
thereby leading to an assertion failure in sane mode and an index out of bounds
exception in insane mode.
For details on how this occurred and what the fix is, please refer to the code
comments in the patch. The d1866_v1 patch does the following:
1. Adds logic to ensure scoped predicates are only pushed
to the appropriate base tables.
2. Adds one line to OptimizerImpl to solve the hang that
was occuring for the second query shown in repro.sql.
The problem there was just that one variable was not
being properly reset when beginning a new round of
optimization.
3. Adds some test cases to verify the changes for #1 and
#2.
Note that the patch is mostly just explanatory comments for existing and new
logic, plus the test cases.
I ran derbyall on Red Hat Linux with ibm142 using sane jars and there were no
new failures. I also ran the full ViewerInit program attached to DERBY-1777
and the program ran to completion without error. (Note that the queries took a
very, very long time to compile, though (longest one took almost 40 minutes).
Unfortunate though that is, I think that's a separate and more general issue
with Derby optimization of subqueries--one to be addressed further down the
road...)
I would appreciate any reviews of this patch--even if it's just a quick read of
the code comments to see if they make sense. Every little bit helps, and as
I'm sure everyone knows by now, optimizer changes are especially worthy of
multiple reviews by as many people as possible...
> Assert failure in sane mode for queries that used to work in 10.1.2.1
> ---------------------------------------------------------------------
>
> Key: DERBY-1866
> URL: http://issues.apache.org/jira/browse/DERBY-1866
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.2.1.4, 10.1.4.0, 10.1.3.2
> Reporter: A B
> Assigned To: A B
> Fix For: 10.2.2.0
>
> Attachments: d1866_v1.patch, derby.log, repro.sql
>
>
> Derby-1777 gives a database and a small program called "ViewerInit" that
> prepares a bunch of large queries involving nested subqueries, unions, and
> join predicates. The actual bug described in DERBY-1777 is an NPE, and
> that's what the patch for DERBY-1777 addresses.
> However, once the NPEs are fixed, some of the queries in that same program
> now fail with ASSERT failures when running in SANE mode; this Jira issue is
> for addressing those assert failures.
> While this does constitute a regression, I don't know yet what the root cause
> of the problem is, so I hesitate to make it a 10.2 blocker--hence urgency is
> "Normal". I'm still investigating the queries to try to track down where the
> problem is, but all I've been able to deduce so far is that a) the assertion
> occurs for a scoped predicate and thus the pushing of join predicates into
> UNIONs is somehow involved, and b) in INSANE mode the query compiles without
> problem and appears (based on some early and very incomplete testing) to
> execute without problem. But more investigation is required to determine if
> the execution/results are actually correct, and to understand more about why
> the assertion is being thrown.
> I'm marking the fixin as 10.2.2.0 for now since I don't enough to make this a
> blocker for 10.2.1. Hopefully more info will be forthcoming...
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
