snapshots - Mailing list pgsql-hackers

From Kovacs Baldvin
Subject snapshots
Date
Msg-id Pine.GSO.4.21.0102041649350.16577-100000@ural2
Whole thread Raw
Responses Re: snapshots  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
Hello.

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.

A few lines in src/backend/tcop/pquery.c runs when
a DECLARE cursor is issued:

>        if (isRetrieveIntoPortal)
>        {
>                PortalExecutorHeapMemory = NULL;
>
>                ProcessPortal(intoName,
>   [...]
>              return;
>     } 
, but I cannot see neither in these, nor in ProcessPortal that
where does it fix the set of rows being visible.

Please help to find it out.

Thanks,
Baldvin






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