| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
| Cc: | Martijn van Oosterhout <kleptog(at)svana(dot)org>, Mischa Sandberg <mischa(at)ca(dot)sophos(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Porting MSSQL to PGSQL (Was: [OT] MySQL is bad, but THIS bad?) |
| Date: | 2006-05-22 23:12:02 |
| Message-ID: | 15889.1148339522@sss.pgh.pa.us |
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"Jim C. Nasby" <jnasby(at)pervasive(dot)com> writes:
> If there was more information than the tuplestore could keep in memory,
> then a TIDstore might be faster, but only if it resulted in reading from
> the heap sequentially, or very near it.
That's easily arranged, use a bitmap indexing data structure.
I think we could probably even live with the structure becoming lossy
under memory pressure: AFAICS, all rows modified by a single query ought
to have the same XMIN/CMIN (or XMAX/CMAX for deleted rows), so it should
be possible to verify whether a particular row is one of the interesting
ones or not.
I think the hard part of this task is designing the API for access to
the rowsets from triggers.
regards, tom lane
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