Fragment elimination on datetime field
- From: Ben Thompson <ben@xxxxxxxxxxxxxxxxxxxxx>
- Date: Thu, 31 Aug 2006 13:05:18 +0100
Hi,
IDS 10.00.xc5
Multiple platforms
I am looking for a way of creating an index on a large table so that fragment elimination will be achieved regularly. The index is simply on a datetime field. I want the index to be maintenance free so I don't want to use specific date ranges and risk that a date can be inserted that doesn't match any of the fragments.
I have tried using the MONTH function as in
fragment by expression
(MONTH (dtfield ) = 1 ) in dbs1 ,
(MONTH (dtfield ) = 2 ) in dbs2 ,
(MONTH (dtfield ) = 3 ) in dbs3 ,
(MONTH (dtfield ) = 4 ) in dbs4 ....
(This is neat in that it splits things up into 12 which is about the maximum number of threads I want to use for PDQ. Of course PDQ is separate to fragment elimination.)
However this doesn't achieve fragment elimination unless you specifically use the MONTH function in your SQL statement and even then it doesn't always work if you filter on this column further. Most of the SQL we run uses date ranges over a week or month period.
I suppose I am looking for a neat way of doing it like there is with the MOD function for id type columns. Can anyone suggest anything?
Ben.
.
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