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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6040) Incorrect row order returned for an ORDER BY on a join of two metadata table functions
Date Fri, 11 Jan 2013 05:06:13 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6040?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13550827#comment-13550827
] 

Dag H. Wanvik commented on DERBY-6040:
--------------------------------------

The first column gets eliminated from the OrderByList in SelectNode#preprocess -> OrderByList#removeConstantColumns
because the code thinks this column references is "TABLE_TYPE", which is part of one of the
where expressions that has a constant.

This mis-identification happens in BinaryRelationOperatorNode#getOperand in these lines:

if (cr.getSource().getColumnPosition() ==
    cRef.getColumnNumber())
{

both sides evaluate to 3. "cr" should point to "T.TABLE_TYPE", and "cRef" should point to
C.TABLE_NAME. So, I believe the wrong number here is assigned to "cr"; it should be 4. Possibly
because FromVTI#genProjectRestrict removes column from the result set that are not used, cf.
his code:

/* Project out any unreferenced columns.  If there are no referenced 
 * columns, generate and bind a single ResultColumn whose expression is 1.
 */
prRCList.doProjection();

I'll see if referencing it makes a difference.


                
> Incorrect row order returned for an ORDER BY on a join of two metadata table functions
> --------------------------------------------------------------------------------------
>
>                 Key: DERBY-6040
>                 URL: https://issues.apache.org/jira/browse/DERBY-6040
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.10.0.0
>            Reporter: Rick Hillegas
>
> Using the metadata table functions introduced by DERBY-6022, I get the wrong row order
on this query:
> select t.table_name c2, c.column_name c3
> from table( getTables( null, '%', '%' ) ) t,
>         table( getColumns( null, '%', '%', '%') ) c
> where c.table_name = t.table_name
> and t.table_type = 'TABLE'
> and c.table_schem = t.table_schem
> order by c2, c3;
> However, I get the correct order on the following query. The good query returns the same
rows but in the correct order. The only difference between the queries is that the bad one
has an extra, NOP join clause.
> Here is the full result of a script showing the problem:
> ij version 10.10
> ij> connect 'jdbc:derby:memory:db;create=true';
> ij> create table t( d int, u varchar( 30 ) );
> 0 rows inserted/updated/deleted
> ij> create table s( d int, u varchar( 30 ) );
> 0 rows inserted/updated/deleted
> ij> call syscs_util.syscs_register_tool( 'databaseMetaData', true );
> 0 rows inserted/updated/deleted
> ij> -- columns are ordered correctly
> select t.table_name c2, c.column_name c3
> from table( getTables( null, '%', '%' ) ) t,
>         table( getColumns( null, '%', '%', '%') ) c
> where c.table_name = t.table_name
> and t.table_type = 'TABLE'
> order by c2, c3;
> C2                                                                                  
                                           |C3                                           
                                                                                  
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> S                                                                                   
                                           |D                                            
                                                                                  
> S                                                                                   
                                           |U                                            
                                                                                  
> T                                                                                   
                                           |D                                            
                                                                                  
> T                                                                                   
                                           |U                                            
                                                                                  
> 4 rows selected
> ij> -- columns are ordered incorrectly
> select t.table_name c2, c.column_name c3
> from table( getTables( null, '%', '%' ) ) t,
>         table( getColumns( null, '%', '%', '%') ) c
> where c.table_name = t.table_name
> and t.table_type = 'TABLE'
> and c.table_schem = t.table_schem
> order by c2, c3;
> C2                                                                                  
                                           |C3                                           
                                                                                  
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> T                                                                                   
                                           |D                                            
                                                                                  
> S                                                                                   
                                           |D                                            
                                                                                  
> T                                                                                   
                                           |U                                            
                                                                                  
> S                                                                                   
                                           |U                                            
                                                                                  
> 4 rows selected

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