| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | josh(at)agliodbs(dot)com |
| Cc: | Oleg Lebedev <oleg(dot)lebedev(at)waterford(dot)org>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: TPC-R benchmarks |
| Date: | 2003-10-08 04:15:57 |
| Message-ID: | 29371.1065586557@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Josh Berkus <josh(at)agliodbs(dot)com> writes:
> To sum up the below: it appears that whenever a set of WHERE conditions
> exceeds a certain level of complexity, the planner just ignores all
> applicable indexes and goes for a seq scan.
It looks to me like the planner is coercing the WHERE clause into
canonical OR-of-ANDs form (DNF). Which is often a good heuristic
but it seems unhelpful for this query.
> How can we fix this?
Feel free to propose improvements to the heuristics in
src/backend/optimizer/prep/prepqual.c ...
regards, tom lane
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