| From: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
|---|---|
| To: | Stephen Frost <sfrost(at)snowman(dot)net>, "tsunakawa(dot)takay(at)fujitsu(dot)com" <tsunakawa(dot)takay(at)fujitsu(dot)com> |
| Cc: | 'David Steele' <david(at)pgmasters(dot)net>, "osumi(dot)takamichi(at)fujitsu(dot)com" <osumi(dot)takamichi(at)fujitsu(dot)com>, 'Kyotaro Horiguchi' <horikyota(dot)ntt(at)gmail(dot)com>, "sawada(dot)mshk(at)gmail(dot)com" <sawada(dot)mshk(at)gmail(dot)com>, "robertmhaas(at)gmail(dot)com" <robertmhaas(at)gmail(dot)com>, "masao(dot)fujii(at)oss(dot)nttdata(dot)com" <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, "ashutosh(dot)bapat(dot)oss(at)gmail(dot)com" <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Disable WAL logging to speed up data loading |
| Date: | 2021-03-22 14:59:04 |
| Message-ID: | 7c2723df1c62b6707055643483b54031d8cb840d.camel@cybertec.at |
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| Lists: | pgsql-hackers |
On Mon, 2021-03-22 at 09:46 -0400, Stephen Frost wrote:
> * tsunakawa(dot)takay(at)fujitsu(dot)com (tsunakawa(dot)takay(at)fujitsu(dot)com) wrote:
> > From: Stephen Frost <sfrost(at)snowman(dot)net>
> > > The argument here seems to stem from the idea that issueing a 'TRUNCATE'
> > > inside the transaction before starting the 'COPY' command is 'too hard'.
> >
> > No, we can't ask using TRUNCATE because the user wants to add data to a table.
>
> First- what are you expecting would actually happen during crash
> recovery in this specific case with your proposed new WAL level?
>
> Second, use partitioning, or unlogged tables (with the patch discussed
> elsewhere to allow flipping them to logged without writing the entire
> thing to WAL).
Perhaps allowing to set unlogged tables to logged ones without writing WAL
is a more elegant way to do that, but I cannot see how that would be any
more crash safe than this patch. Besides, the feature doesn't exist yet.
So I think that argument doesn't carry much weight.
Yours,
Laurenz Albe
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