I have seen GENROW many times in the Optimized SQL statement in the exfmt output. In
my case, this was related to the eliminating unqualified branches in the UNION ALL
VIEW when joined to a table. In that case, the unqualified branch is transformed to a
nested loop join (NLJOIN) with the outer input (left hand side) is a GENROW and the
inner input (right hand side) is the table name (if doing table scan) or one of the
index of that table (if doing index scan) of the unqualified
branch.
The way the plan works is it starts to evaluate the predicate in the
GENROW, which is in the form of:
(query predicate) AND (view definition predicate)
For example,
month_id = 72001 AND month_id in (102000,112000,122000)
In this case, the predicate will return false and the GENROW will produce no row. The
NLJOIN will not access its inner input, which is the access to the table (or index).
Sorry, if I cannot explain properly.
Ellen Klebaner-Reys
Data Management Services
Inovant - a Visa Solutions Company
[EMAIL PROTECTED]/650-432-1746 m/s: 3125-1D
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Monday, September 08, 2003 2:35 PM
To: [EMAIL PROTECTED]
Subject: [DB2EUG] SYSIBM.GENROW showing up in explains?
Somehow SYSIBM.GENROW keeps popping up in explain diagrams. Can't find this
object however. Does anyone know what's the purpose of this one?
Thanks,
Tim
-
::: When replying to the list, please use 'Reply-All' and make sure
::: a copy goes to the list ([EMAIL PROTECTED]).
*** To unsubscribe, send 'unsubscribe' to [EMAIL PROTECTED]
*** For more information, check http://www.db2eug.uni.cc
-
::: When replying to the list, please use 'Reply-All' and make sure
::: a copy goes to the list ([EMAIL PROTECTED]).
*** To unsubscribe, send 'unsubscribe' to [EMAIL PROTECTED]
*** For more information, check http://www.db2eug.uni.cc
