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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5010) [patch] bad equivalence check
Date Mon, 27 Jun 2011 15:05:48 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5010?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13055592#comment-13055592
] 

Knut Anders Hatlen commented on DERBY-5010:
-------------------------------------------

Hi Jayaram,

I think these constants come from C_NodeTypes:

>    static final int COLUMN_REFERENCE = 62;

and

>    static final int BASE_COLUMN_NODE = 94;

So it looks like we're calling isEquivalent() to check whether a ColumnReference instance
is equivalent to a BaseColumnNode in this query.

I think the ColumnReference here is the reference to C1 in the GROUP BY clause, and to exercise
the code using a variant of this query, we'd have to get the GROUP BY clause to contain a
BaseColumnNode somehow. I'm afraid I don't have any good ideas on how to do that (I'm not
even sure if it's possible).

> [patch] bad equivalence check
> -----------------------------
>
>                 Key: DERBY-5010
>                 URL: https://issues.apache.org/jira/browse/DERBY-5010
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.7.1.1
>            Reporter: Dave Brosius
>            Priority: Trivial
>             Fix For: 10.8.1.5
>
>         Attachments: IsEquivalent_DoNotCommit_June11.txt, IsEquivalent_Donotcommit_june14.txt,
bad_equivalence_check.diff, derby.log, derby.log, june15.out, runoutputJune14.out, runoutputJune2.out
>
>   Original Estimate: 1h
>  Remaining Estimate: 1h
>
> code attempts to compare two BaseColumnNodes but doesn't compare the tableName correctly.

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