db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4695) Internal assignment of tablenumer, columnnumber looks wrong in query tree, although no ill effects are seen.
Date Wed, 23 Jun 2010 13:12:49 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4695?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12881680#action_12881680
] 

Dag H. Wanvik commented on DERBY-4695:
--------------------------------------

Thanks for the encouragement, Bryan :) I'm afraid I am not quite yet
in the position to replace the existing machinery with a better
design, but I am slowly learning more about this area, too.

Meanwhile, I feel more confident that the patch for DERBY-4679 (with
the added followup-patch) would be safe to back-port from the following
reasoning:

- the seen inconsistency lies in the columnNumber, not the tableNumber

- the (tn, cn)-based lookup used in the patch for DERBY-4679 only
  considers RCs with a correct table number (and column number).  If
  the column number in the column reference should be wrong (as
  documented in this issue), the added sanity check for the column
  name to also match, would catch and discard the candidate RC, and
  make the (tn, cn)-based lookup return null.
  I.e. it can not return false positives.

- subsequently, we would fall back on the exisiting columnName based
  lookup (exisiting behavior)

This leads me to conclude that the code would always be an improvement over the current solution.

So, I intend to back-port DERBY-4679 to the 10.6 branch while I
continue to look for a better solution that would:

         a) keep numbering consistent, if achievable
         b) document the invariants if I can establish any
         b) make the variant query i constructed for DERBY-4679 which still fails (the one
that
         contains a subquery) also work.


> Internal assignment of tablenumer, columnnumber looks wrong in query tree, although no
ill effects are seen.
> ------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4695
>                 URL: https://issues.apache.org/jira/browse/DERBY-4695
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.7.0.0
>            Reporter: Dag H. Wanvik
>            Assignee: Dag H. Wanvik
>            Priority: Minor
>         Attachments: derby.log, why-ij-can-do-without-2nd-bind.txt, why-loj-needs-2nd-bind.txt
>
>
> While looking into derby-4679, I also looked at the query in
> derby-2526 to validate that my changes also worked for that variant of
> the problem.
> During inspection of the query trees after the bind phase, I found one
> instance in which the pair (tablenumber, columnnumber) of a column
> reference was wrong. Although it did not seem to impact the query
> result, I note it here as as something we should probably investiate
> as it may be a symptom an underlying problem, or a potential for
> future problems.
> The query looks like this:
> select b3.* from b3 join bvw on (b3.c8 = bvw.c5) join b4 on (bvw.c1 = b4.c7) where b4.c4
= 42"
> and the underlying DDL is this:
> create table b2 (c1 int, c2 int, c3 char(1), c4 int, c5 int, c6 int);
> create table b4 (c7 int, c4 int, c6 int);
> create table b3 (c8 int, c9 int, c5 int, c6 int);
> create table b (c1 int, c2 int, c3 char(1), c4 int, c5 int, c6 int);
> create view bvw (c5, c1 ,c2 ,c3 ,c4) as
> select c5, c1 ,c2 ,c3 ,c4 from b2 union
> select c5, c1 ,c2 ,c3 ,c4 from b;
> create view bvw2 (c1 ,c2 ,c3 ,c4 ,c5) as
> After the bind phase, the join clause "bvw.c1 = b4.c7" has the
> following entry for the column reference bvw.C1:
>           
>           tableNumber: 1
>           columnNumber: 6
> The problem is that the node with tablenumber 1 is bvw, which is the
> view with the subquery for the union, which has only 5 resulting
> columns, so 6 must be wrong. Although both the view participant tables
> (b, b2) both have six column, the view does not. In any case, C1 is
> column 2 in the view and column 2 in the two union selects from both b
> and b2.
> C1 is however, column 6 of the join node resulting from "select b3.*
> from b3 join bvw on (b3.c8 = bvw.c5)", but the correct table number for
> that would be 5, not 1.
> So, it would seem the table number has been bound to the bvw view's
> result set, but the column number has been bound to the innermost join
> node's result set. This looks worrying to me.
> See derby.log attached for the full dump of the query tree after the
> bind phase.
> sourceResultSet:                                    
>     org.apache.derby.impl.sql.compile.FromSubquery@12789d2
>     correlation Name: BVW
>     null
>     tableNumber 1 <------------------------------------------- Note!
>     level 0
>     resultSetNumber: 0
>     referencedTableMap: null
>     statementResultSet: false
>     resultColumns:                                      
>         org.apache.derby.impl.sql.compile.ResultColumnList@c943d1
>         indexRow: false
>         orderBySelect: 0
>         [0]:                                        
>         org.apache.derby.impl.sql.compile.ResultColumn@d3c6a3
>         ***truncated***
>         [1]:                                        
>         org.apache.derby.impl.sql.compile.ResultColumn@18352d8
>         exposedName: C1
>         name: C1
>         tableName: null
>         isDefaultColumn: false
>         wasDefaultColumn: false
>         isNameGenerated: false
>         sourceTableName: B2
>         type: INTEGER
>         columnDescriptor: null
>         isGenerated: false
>         isGeneratedForUnmatchedColumnInInsert: false
>         isGroupingColumn: false
>         isReferenced: true
>         isRedundant: false
>         virtualColumnId: 2
>         resultSetNumber: -1
>         dataTypeServices: INTEGER
>         expression:                                         
>             org.apache.derby.impl.sql.compile.VirtualColumnNode@b40ec4
>             dataTypeServices: null
>             sourceColumn:                                               
>                 org.apache.derby.impl.sql.compile.ResultColumn@1d95da8
>                 ***truncated***
>             sourceResultSet:                                                
>                 org.apache.derby.impl.sql.compile.UnionNode@14d7745
>                 ***truncated***
>         [2]:                                        
>         org.apache.derby.impl.sql.compile.ResultColumn@13576a2
>         exposedName: C2
>         name: C2
>         tableName: null
>         isDefaultColumn: false
>         wasDefaultColumn: false
>         isNameGenerated: false
>         sourceTableName: B2
>         type: INTEGER
>         columnDescriptor: null
>         isGenerated: false
>         isGeneratedForUnmatchedColumnInInsert: false
>         isGroupingColumn: false
>         isReferenced: true
>         isRedundant: false
>         virtualColumnId: 3
>         resultSetNumber: -1
>         dataTypeServices: INTEGER
>         expression:                                         
>             org.apache.derby.impl.sql.compile.VirtualColumnNode@ff8c74
>             dataTypeServices: null
>             sourceColumn:                                               
>                 org.apache.derby.impl.sql.compile.ResultColumn@61736e
>                 ***truncated***
>             sourceResultSet:                                                
>                 org.apache.derby.impl.sql.compile.UnionNode@14d7745
>                 ***truncated***
>         [3]:                                        
>         org.apache.derby.impl.sql.compile.ResultColumn@15e2ccd
>         exposedName: C3
>         name: C3
>         tableName: null
>         isDefaultColumn: false
>         wasDefaultColumn: false
>         isNameGenerated: false
>         sourceTableName: B2
>         type: CHAR(1)
>         columnDescriptor: null
>         isGenerated: false
>         isGeneratedForUnmatchedColumnInInsert: false
>         isGroupingColumn: false
>         isReferenced: true
>         isRedundant: false
>         virtualColumnId: 4
>         resultSetNumber: -1
>         dataTypeServices: CHAR(1)
>         expression:                                         
>             org.apache.derby.impl.sql.compile.VirtualColumnNode@1cf7491
>             dataTypeServices: null
>             sourceColumn:                                               
>                 org.apache.derby.impl.sql.compile.ResultColumn@11946c2
>                 ***truncated***
>             sourceResultSet:                                                
>                 org.apache.derby.impl.sql.compile.UnionNode@14d7745
>                 ***truncated***
>         [4]:    <----------------------------------------- highest column number is
5 (index is zero-based)
>         org.apache.derby.impl.sql.compile.ResultColumn@edf730
>         exposedName: C4
>         name: C4
>         tableName: null
>         isDefaultColumn: false
>         wasDefaultColumn: false
>         isNameGenerated: false
>         sourceTableName: B2
>         type: INTEGER
>         columnDescriptor: null
>         isGenerated: false
>         isGeneratedForUnmatchedColumnInInsert: false
>         isGroupingColumn: false
>         isReferenced: true
>         isRedundant: false
>         virtualColumnId: 5
>         resultSetNumber: -1
>         dataTypeServices: INTEGER
>         expression:                                         
>             org.apache.derby.impl.sql.compile.VirtualColumnNode@ff94b1
>             dataTypeServices: null
>             sourceColumn:                                               
>                 org.apache.derby.impl.sql.compile.ResultColumn@17a4989
>                 ***truncated***
>             sourceResultSet:                                                
>                 org.apache.derby.impl.sql.compile.UnionNode@14d7745
>                 ***truncated***
>     subquery:                                       
>         org.apache.derby.impl.sql.compile.UnionNode@14d7745
>         ***truncated***

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message