Re: Ad Hoc Indexes

Justin wrote:
> Then why are the estimates so far off?

Perhaps a really high correlation between those records where coitem_status = 'O' and those records in your date range. The planner estimates 1 row when restricting by both restrictions, whereas there where 458. The 1 row was probably a result of a small % for status='O' multiplied by a small % for the date range.

> If estimates where correct would it improve the performance that much.

Possibly, but a better performance gain might be obtained by rewriting the query, changing the case expression to something along the lines of:

coalesce((
select wrkcnt_code || ' Operation Completed :' || cast(wooper_seqnumber as text)
from wooper inner join wrkcnt on wrkcnt_id = wooper_wrkcnt_id
where wooper_rncomplete = true and wooper_wo_id = coitem_order_id
order by wooper_seqnumber desc limit 1
),'No Operation Completed') as LastFinshedOp

regards,
Stephen Denne.

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