| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: DBT-3 with SF=20 got failed |
| Date: | 2015-09-24 17:04:55 |
| Message-ID: | 12848.1443114295@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
> But what about computing the number of expected batches, but always
> start executing assuming no batching? And only if we actually fill
> work_mem, we start batching and use the expected number of batches?
Hmm. You would likely be doing the initial data load with a "too small"
numbuckets for single-batch behavior, but if you successfully loaded all
the data then you could resize the table at little penalty. So yeah,
that sounds like a promising approach for cases where the initial rowcount
estimate is far above reality.
But I kinda thought we did this already, actually.
regards, tom lane
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