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From "Mamta A. Satoor (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DERBY-4631) Wrong join column returned by right outer join with NATURAL or USING and territory-based collation
Date Wed, 29 Feb 2012 01:30:06 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4631?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mamta A. Satoor updated DERBY-4631:
-----------------------------------

    Attachment: DERBY_4631_patch5_diff.txt

Hi Mike,

thanks for reviewing patch 4. Here are some comments to your feedback(Attaching a new patch
DERBY_4631_patch5_diff.txt which takes care of some of your comments.)

1)ResultColumn:
********
Mike's comment - There is a lot of checking for instances here, is there anyway to do this
work in the affected nodes like HalfOuterJoinNode?
********
Yes, I am concerned about the instance checking too but I had researched into putting the
code in HalfOuterJoinNode and found that HalfOuterJoinNode does not ever get to see the ResultColumns
for the query and hence it has no way of marking those ResultColumns as join columns.

********
Mike's comment - At end of ResultColumn changes why do you check and set for one of the new
fields and not the other?
********
I was trying to follow the existing code where the boolean kinds of fields are first checked
and then set to true if the check returned true. rightOuterJoinUsingClause is a boolean field
and hence I checked for the return value and then set the new object's value to true. But
joinResultSet is a non-boolean field and hence I simply used it's value to set new object's
joinResultSet value. For clarity, I will go ahead and replace following
  		newResultColumn.setJoinResultset(getJoinResultSet());
with
  		if (getJoinResultSet() != null) {
	  		newResultColumn.setJoinResultset(getJoinResultSet());
  		}

2)ResultColumnList.java:
********
Mike's comment - get rid of the commented out line of code that you fixed with patch 4
********
Removed it. 

********
Mike's comment - a comment in allExpressionsAreColumns explaining why returning false for
isRightOuterJoinUsingClause would be useful. 
********
Added a comment.

********
Mike's comment - in mapSourceColumns() what does the -1 for right outer join columns mean?

********
allExpressionsAreColumns() uses the -1 value set by mapSourceColumns() to decide if there
are columns which require special consideration during code generation. When mapSourceColumns()
assigns -1 to right outer join column, allExpressionsAreColumns() will return false. This
will allow Derby to later generate code equivalent to COASLECE for right outer join columns(this
code generation happens in newly added code in ResultColumnList.generateCore.)

********
Mike's comment - typo - search for "righ " 
********
Fixed it.

********
Mike's comment - would be nice to have comments for setJoinResultset and setRightOuterJoinUsingClause,
maybe something about what is expected to call this routine and in what circumstances. 
********
Added comments around for both those methods.

Additionally, took care of some indentation problems with the code.

                
> 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, DERBY_4631_patch4_diff.txt, DERBY_4631_patch5_diff.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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