| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Kovacs Baldvin <kb136(at)hszk(dot)bme(dot)hu> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: snapshots |
| Date: | 2001-02-04 19:34:02 |
| Message-ID: | 6834.981315242@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Kovacs Baldvin <kb136(at)hszk(dot)bme(dot)hu> writes:
> Could somebody explain me the mechanism in the backend,
> which is responsible for the followings. (I tried to
> look around snapshots, but couldnt figure out th answer).
> In a transaction, isol. read comitted, a select from a
> table can see the comitted changes by others, but
> a previously declared cursor can not.
Yup. The snapshot used for a particular query is nailed down when
ExecutorStart() is called. Look around for uses of QuerySnapshot
and estate->es_snapshot.
regards, tom lane
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