| From: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
|---|---|
| To: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, michael(at)paquier(dot)xyz |
| Cc: | nathandbossart(at)gmail(dot)com, postgres(at)jeltef(dot)nl, smithpb2250(at)gmail(dot)com, vignesh21(at)gmail(dot)com, jakub(dot)wartak(at)enterprisedb(dot)com, stark(dot)cfm(at)gmail(dot)com, barwick(at)gmail(dot)com, jchampion(at)timescale(dot)com, pryzby(at)telsasoft(dot)com, tgl(at)sss(dot)pgh(dot)pa(dot)us, rjuju123(at)gmail(dot)com, jakub(dot)wartak(at)tomtom(dot)com, pgsql-hackers(at)lists(dot)postgresql(dot)org, bharath(dot)rupireddyforpostgres(at)gmail(dot)com |
| Subject: | Re: In-placre persistance change of a relation |
| Date: | 2024-10-28 13:33:41 |
| Message-ID: | 9d45c156-caad-4197-b77d-47dfbbe74eb4@iki.fi |
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| Lists: | pgsql-hackers |
On 31/08/2024 19:09, Kyotaro Horiguchi wrote:
> Subject: [PATCH v34 03/16] Remove function for retaining files on outer
> transaction aborts
>
> The function RelationPreserveStorage() was initially created to keep
> storage files committed in a subtransaction on the abort of outer
> transactions. It was introduced by commit b9b8831ad6 in 2010, but no
> use case for this behavior has emerged since then. If we move the
> at-commit removal feature of storage files from pendingDeletes to the
> UNDO log system, the UNDO system would need to accept the cancellation
> of already logged entries, which makes the system overly complex with
> no benefit. Therefore, remove the feature.
I don't think that's quite right. I don't think this was meant for
subtransaction aborts, but to make sure that if the top-transaction
aborts after AtEOXact_RelationMap() has already been called, we don't
remove the new relation. AtEOXact_RelationMap() is called very late in
the commit process to keep the window as small as possible, but if it
nevertheless happens, the consequences are pretty bad if you remove a
relation file that is in fact needed.
--
Heikki Linnakangas
Neon (https://neon.tech)
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