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choice of clustering index


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jzhardy

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Joined: 31 Oct 2006
Posts: 91
Location: brisbane

PostPosted: Tue Feb 09, 2021 8:17 am
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I have a table T that I want to index on a date column (ASC) + Instance ID (ASC) to support the primary workload.

The date values will *mostly* be received in ascending order, however we need to allow that some (up to 5 %) will be out of order, by as much as one week.

So, a representative sample might look like:

Code:

Received on      Date value          count(*)         Instance Id allocated

1/1/21           1/1/21              1000             1 to 1000
2/1/21           2/1/21              1200             1001 to 2200
3/1/21           3/1/21              800              2201 to 3000
3/1/21           28/12/20            6                3001 to 3006
4/1/21           4/1/21              900              3007 to 3906



My question is whether a single clustered index on Date + Instance ID would be sufficient - or - to cater for the number of out-of-sequence date values , should I have Date + Instance ID as non-clustered, and add a clustered index on , say, Month(Date column) - assuming this is supported in db2 ?

so:

option A :

clustered index on Date-col ASC + instance ID ASC


option B :

non clustered index on Date-col ASC + instance ID ASC
clustered index on Month(date-col)

or ?
Option C :

non clustered index on Date-col ASC + instance ID ASC
clustered index on date-column



I expect table T to grow quickly and into the millions. No Update operations on the Date column allowed. Also, (at this stage), no physical deletes allowed
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Rohit Umarjikar

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Joined: 21 Sep 2010
Posts: 2671
Location: NYC,USA

PostPosted: Tue Feb 09, 2021 8:34 am
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If you are not a DBA then please talk to your site DBA.
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guptae

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Joined: 14 Oct 2005
Posts: 1208
Location: Bangalore,India

PostPosted: Thu Feb 11, 2021 5:18 pm
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Hey There,

How data is going to be fetched from this table?
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jzhardy

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Joined: 31 Oct 2006
Posts: 91
Location: brisbane

PostPosted: Mon Feb 15, 2021 2:20 am
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fetch order is Date DESC, Instance ID DESC
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