Re: Document efficient self-joins / UPDATE LIMIT techniques. - Mailing list pgsql-hackers

From Corey Huinker
Subject Re: Document efficient self-joins / UPDATE LIMIT techniques.
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Msg-id CADkLM=dswiXCCYjC+Q=XCOHjQjF8gWr-0Q_Ljkwqive=0MeKdQ@mail.gmail.com
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In response to Re: Document efficient self-joins / UPDATE LIMIT techniques.  ("Joel Jacobson" <joel@compiler.org>)
Responses Re: Document efficient self-joins / UPDATE LIMIT techniques.
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> As for whether it's commonplace, when I was a consultant I had a number
> of customers that I had who bemoaned how large updates caused big
> replica lag, basically punishing access to records they did care about
> in order to properly archive or backfill records they don't care about.
> I used the technique a lot, putting the update/delete in a loop, and
> often running multiple copies of the same script at times when I/O
> contention was low, but if load levels rose it was trivial to just kill
> a few of the scripts until things calmed down.

I've also used the technique quite a lot, but only using the PK,
didn't know about the ctid trick, so many thanks for documenting it.

tid-scans only became a thing a few versions ago (12?). Prior to that, PK was the only way to go.

 

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