Re: Commit every N rows in PL/pgsql

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Len Walter <len(dot)walter(at)gmail(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Commit every N rows in PL/pgsql
Date: 2010-05-26 08:47:03
Message-ID: AANLkTiligaKIeNWFkhAFGTUNchl-TMV51QnyRJuTjOIE@mail.gmail.com
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Hello

it is useless in PostgreSQL - it isn't important if you commit one or
billion updated rows. PostgreSQL has different implementation of
transactions, so some Oracle's issues are not here.

Regards
Pavel Stehule

2010/5/26 Len Walter <len(dot)walter(at)gmail(dot)com>:
> Hi,
> I need to populate a new column in a Postgres 8.3 table. The SQL would be
> something like "update t set col_c = col_a + col_b". Unfortunately, this
> table has 110 million rows, so running that query runs out of memory.
> In Oracle, I'd turn auto-commit off and write a pl/sql procedure that keeps
> a counter and commits every 10000 rows (pseudocode):
> define cursor curs as select col_a from t
> while fetch_from_cursor(curs) into a
>      update t set col_c = col_a + col_b where col_a = a
>      i++
>      if i > 10000
>          commit; i=0;
>      end if;
>      commit;
> PL/pgsql doesn't allow that because it doesn't support nested transactions.
> Is there an equivalent Postgres way of doing this?
> cheers,
> Len
> --
> len(dot)walter(at)gmail(dot)com skype:lenwalter  msn:len(dot)walter(at)gmail(dot)com
>

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