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From Mike Matrigali <mikem_...@sbcglobal.net>
Subject Re: Question on why indexStat deamon is being triggered
Date Mon, 02 Apr 2012 19:05:27 GMT
Kristian Waagan wrote:

>> Does the daemon when it determines an update is necessary, go through 
>> the udpate stat path telling it to update stats on all indexes or does
>> it call update stat one index at a time?
> 
> It goes through the path where all indexes are updated.
> This can be changed in two locations if we wish to:
>  1) In the scheduling call (currently it takes a TableDescriptor as an 
> argument)
>  2) Inside the daemon itself, where we could (re-)check the status of 
> each index before processing it.
> 
> When a statement is compiled the code checks the index cardinality 
> statistics for staleness if there are qualifying indexes for the query. 
> Once a stale index is found for a base table, the table descriptor is 
> stashed aside to be submitted to the daemon as a unit of work (and we 
> stop checking the rest of the indexes of that table).
> 
> Currently, the only time  a unit of work can be scheduled is when a 
> select statement using an index is compiled/recompiled.
> 
> 
Thanks for quick answer.  I think current behavior is fine, just wanted
to understand it.  I think it makes sense to update all the stats on
a single table at one time, especially since our staleness metric
is related to table size so likely to apply to all stats on the table.

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