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Bind Peeking only for "known" columns?

fjfrankenJan 14 2015 — edited Jan 15 2015

Hi all,

We are working on our 11.2.0.3 RAC (on AIX 7.1) database on trying to figure out why a certain repeated query ( batch load) is not using the correct execution plan.

The query itself looks like:

select CATENTRY_ID from CATENTRY where ((PARTNUMBER=:1 ) OR ((0 = :2 ) AND (PARTNUMBER IS NULL))) and ((MEMBER_ID=:3 ) OR ((0 = :4 ) AND (MEMBER_ID IS NULL)));

This query is an IBM Webshere internal query, which therefore is unchangeable.

The table in question has an Index available on PARTNUMBER & MEMBER_ID

The execution plan however looks like

The execution plan of the above statement looks like:

Execution Plan

----------------------------------------------------------

0 SELECT STATEMENT Optimizer Mode=ALL_ROWS (Cost=2038 Card=1 Bytes=23)

1 0 TABLE ACCESS FULL WCSADMIN.CATENTRY (Cost=2038 Card=1 Bytes=23)

So a FTS scan is used where an Index-lookup would be expected.

The values passed to this query are e.g.:

:1 = XA-GED-1068849

:2 = 1

:3 = -6000

:4 = 1

With the part of the WHERE CLAUSE then having ((0=1) AND (PARTNUMBER IS NULL)) and the same for ((0=1) AND (MEMBER_ID IS NULL)) would result in an Index lookup.:

select

catentry_id

from catentry

where ( (partnumber = 'XA-GED-5702810')

  or ( (0 = 1)

  and (partnumber is null)))

and ( (member_id = -6000)

  or ( (0 = 1)

  and (member_id is null))) ;

Execution Plan

----------------------------------------------------------

0 SELECT STATEMENT Optimizer Mode=ALL_ROWS (Cost=3 Card=1 Bytes=23)

1 0 TABLE ACCESS BY INDEX ROWID WCSADMIN.CATENTRY (Cost=3 Card=1 Bytes=23)

2 1 INDEX UNIQUE SCAN WCSADMIN.I0000064 (Cost=2 Card=1)

Somewhere in the parsing of the query the optimizer does not have/use all the information needed to determine the correct plan, allthough the tracefile shows all values are captured correctly

I would expect that the optimizer would "PEEK" all available variables to determine the best execution plan.

It looks however that the two BINDs for the "0=:2" and "0=:4" are not "peeked" and therefore not used, which results in a Full Table Scan as the PARTNUMBER IS NULL and MEMBER_ID IS NULL are not skipped.

Can anyone confirm that only BINDs for "existing/real" columns are peeked??

And is this configurable ??

Thanks

FJ Franken

This post has been answered by Jonathan Lewis on Jan 14 2015
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Locked on Feb 12 2015
Added on Jan 14 2015
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