[
http://issues.apache.org/jira/browse/DERBY-649?page=comments#action_12360997 ]
Daniel John Debrunner commented on DERBY-649:
---------------------------------------------
I think I've found the bug in the patch. I'd appreciate any optimizer experts
looking at this.
In PredicateList.pushExpressionsIntoSelect when the predicate is copied, any
type of binary relational node can be copied, but the new relational node
create is always an quality node, it is not based upon the type being pushed.
I'm replacing this code, difference is first argument to getNode() :
around line 1438 - changes would also be made to te variable name, to correctly
represent its use.
BinaryRelationalOperatorNode newEquals =
(BinaryRelationalOperatorNode)
getNodeFactory().getNode(
C_NodeTypes.BINARY_EQUALS_OPERATOR_NODE,
newCRNode,
opNode.getRightOperand(),
getContextManager());
with
BinaryRelationalOperatorNode newEquals =
(BinaryRelationalOperatorNode)
getNodeFactory().getNode(
opNode.getNodeType(),
newCRNode,
opNode.getRightOperand(),
getContextManager());
I'd incorrectly assumed in the review that the (incorrect) new equality node
was related to the boolean constant TRUE being created. So sort of '(pushed
expression) = TRUE' was being pushed and required for some reason. I knew there
was a good reason I'd asked for comments on this code section:
> Dec 15th 08:19
> For example, why do we need a new nodes that
> represent '= TRUE', I'm sure it's required but to a reader of the code
it's not obvious why.
> Useful indexes not used in UNION ALL
> ------------------------------------
>
> Key: DERBY-649
> URL: http://issues.apache.org/jira/browse/DERBY-649
> Project: Derby
> Type: Bug
> Reporter: Rick Hillegas
> Attachments: DERBY-649.patch, DERBY-649.stat
>
> Frederic Moreau reports
> (http://mail-archives.apache.org/mod_mbox/db-derby-user/200510.mbox/browser):
> Hello,
> The optimizer does not take my indexes into account when I do a select on
> a 'UNION ALL' type of view ; therefore, table scans are done and
> performances are bad.
> Note : my indexes are taken into account if I try equivalent selects on
> tables (instead of views).
> Please find below a sample illustrating the problem using the
> RUNTIMESTATISTICS calls.
> Could anynone help me on this subject ?
> Thank you.
> My cloudscape version is the 10.0.2.1 one.
> I also tried it on the 10.1.1.0 version (same result).
> c:\>java -classpath
> "%CLOUDSCAPE_INSTALL%\lib\derbyclient.jar;%CLOUDSCAPE_INSTALL%\lib\derbytools.jar"
>
> -Dij.driver=org.apache.derby.jdbc.ClientDriver
> -Dij.protocol=jdbc:derby://localhost:1527/ -Dij.user=APP -Dij.password=APP
> -Dij.maximumDisplayWidth=32768 org.apache.derby.tools.ij ij> connect
> 'testdb' ;
> ij> ;
> ij> create table test.table1(a integer, b integer, c integer);
> ij> create index test.table1idx on test.table1(b);
> ij> ;
> ij> create table test.table2(a integer, b integer, c integer);
> ij> create index test.table2idx on test.table2(b);
> ij> ;
> ij> create view test.view0 as select all a,b from test.table1 union all
> select a,b from test.table2;
> ij> ;
> ij> CALL SYSCS_UTIL.SYSCS_SET_RUNTIMESTATISTICS(1);
> ij> select a from test.table1 where b=25;
> ij> VALUES SYSCS_UTIL.SYSCS_GET_RUNTIMESTATISTICS();
> ...
> Index Scan ResultSet for TABLE1 using index TABLE1IDX at read
> committed isolation level using instantaneous share row locking chosen by
> the optimizer
> ...
> ij> select a from test.table2 where b=25;
> ij> VALUES SYSCS_UTIL.SYSCS_GET_RUNTIMESTATISTICS();
> ...
> Index Scan ResultSet for TABLE2 using index TABLE2IDX at read
> committed isolation level using instantaneous share row locking chosen by
> the optimizer
> ...
> ij> select a from test.view0 where b=25;
> ij> VALUES SYSCS_UTIL.SYSCS_GET_RUNTIMESTATISTICS();
> ...
> Table Scan ResultSet for TABLE1 at read committed isolation level
> using share row locking chosen by the optimizer
> ...
> Table Scan ResultSet for TABLE2 at read committed isolation level
> using share row locking chosen by the optimizer
> ...
> ij> ;
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