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Date: Tue, 21 Feb 2012 01:21:34 +0000 (UTC)
From: "Mamta A. Satoor (Commented) (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
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Subject: [jira] [Commented] (DERBY-4631) Wrong join column returned by right
 outer join with NATURAL or USING and territory-based collation
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    [ https://issues.apache.org/jira/browse/DERBY-4631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13212276#comment-13212276 ] 

Mamta A. Satoor commented on DERBY-4631:
----------------------------------------

I have been working on writing more tests for JOINs to see nothing breaks with my changes. Unfortunately, the following script with the patch DERBY_4631_patch3_diff.txt patch gives  ERROR 38000: The exception 'java.lang.ArrayIndexOutOfBoundsException: Array index out of range: -2' was thrown while evaluating an expression.

connect 'jdbc:derby:db1;create=true;territory=en_US;collation=TERRITORY_BASED:SECONDARY'; 
CREATE TABLE derby4631_t1(x varchar(5));
INSERT INTO derby4631_t1 VALUES 'A','B';
CREATE TABLE derby4631_t2(x varchar(5));
INSERT INTO derby4631_t2 VALUES 'b','c';
CREATE TABLE derby4631_t3(x1 varchar(5), y1 varchar(5));
INSERT INTO derby4631_t3 
        		SELECT x, 
        		'a'
          		FROM derby4631_t2 NATURAL RIGHT OUTER JOIN derby4631_t1;

I am debugging the patch to see what is causing the failure.
                
> Wrong join column returned by right outer join with NATURAL or USING and territory-based collation
> --------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4631
>                 URL: https://issues.apache.org/jira/browse/DERBY-4631
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.6.1.0
>            Reporter: Knut Anders Hatlen
>            Assignee: Mamta A. Satoor
>              Labels: derby_triage10_8
>         Attachments: DERBY_4631_not_for_commit_patch1_diff.txt, DERBY_4631_not_for_commit_patch1_stat.txt, DERBY_4631_not_for_commit_patch2_diff.txt, DERBY_4631_not_for_commit_patch2_stat.txt, DERBY_4631_patch3_diff.txt, DERBY_4631_patch3_stat.txt
>
>
> SQL:2003 says that the join columns in a natural join or in a named
> columns join should be added to the select list by coalescing the
> column from the left table with the column from the right table.
> Section 7.7, <joined table>, syntax rules:
> > 1) Let TR1 be the first <table reference>, and let TR2 be the <table
> > reference> or <table factor> that is the second operand of the
> > <joined table>. Let RT1 and RT2 be the row types of TR1 and TR2,
> > respectively. Let TA and TB be the range variables of TR1 and TR2,
> > respectively. (...)
> and
> > 7) If NATURAL is specified or if a <join specification> immediately
> > containing a <named columns join> is specified, then:
> (...)
> > d) If there is at least one corresponding join column, then let SLCC
> > be a <select list> of <derived column>s of the form
> >
> > COALESCE ( TA.C, TB.C ) AS C
> >
> > for every column C that is a corresponding join column, taken in
> > order of their ordinal positions in RT1.
> For a right outer join, Derby doesn't use COALESCE(TA.C, TB.C), but
> rather just TB.C (the column in the right table) directly.
> This is in most cases OK, because COALESCE(TA.C, TB.C) = TB.C is an
> invariant in a right outer join. (Because TA.C is either NULL or equal
> to TB.C.)
> However, in a database with territory-based collation, equality
> between two values does not mean they are identical, especially now
> that the strength of the collator can be specified (DERBY-1748).
> Take for instance this join:
> ij> connect 'jdbc:derby:testdb;create=true;territory=en_US;collation=TERRITORY_BASED:SECONDARY';
> ij> create table big(x varchar(5));
> 0 rows inserted/updated/deleted
> ij> insert into big values 'A','B','C';
> 3 rows inserted/updated/deleted
> ij> create table small(x varchar(5));
> 0 rows inserted/updated/deleted
> ij> insert into small values 'b','c','d';
> 3 rows inserted/updated/deleted
> ij> select x, t1.x, t2.x, coalesce(t1.x, t2.x) from small t1 natural right outer join big t2;
> X    |X    |X    |4    
> -----------------------
> A    |NULL |A    |A    
> B    |b    |B    |b    
> C    |c    |C    |c    
> 3 rows selected
> I believe that the expected result from the above query is that the
> first column should have the same values as the last column. That is,
> the first column should contain {'A', 'b', 'c'}, not {'A', 'B', 'C'}.

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