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Re: POC: Cleaning up orphaned files using undo logs - Mailing list pgsql-hackers

From Thomas Munro
Subject Re: POC: Cleaning up orphaned files using undo logs
Date
Msg-id CA+hUKGLvQSxXnwsqU1exWuPSH7VOouG=-s1Rradw7o+rwFKzWg@mail.gmail.com
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In response to Re: POC: Cleaning up orphaned files using undo logs  (Antonin Houska <ah@cybertec.at>)
Responses Re: POC: Cleaning up orphaned files using undo logs  (Antonin Houska <ah@cybertec.at>)
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On Wed, Sep 29, 2021 at 8:18 AM Antonin Houska <ah@cybertec.at> wrote:
> I'm just trying to use the existing infrastructure: the effect of DROP TABLE
> also appear to be performed by the checkpointer. However I don't know why the
> unlinks need to be performed by the checkpointer.

For DROP TABLE, we leave an empty file (I've been calling it a
"tombstone file") so that GetNewRelFileNode() won't let you reuse the
same relfilenode in the same checkpoint cycle.  One reason is that
wal_level=minimal has a data-eating crash recovery failure mode if you
reuse a relfilenode in a checkpoint cycle.

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