| From: | Carlos Alves <carlos(dot)alves(at)tecnisys(dot)com(dot)br> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-general(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Question about tuple´s lock |
| Date: | 2023-10-24 20:43:07 |
| Message-ID: | d9f17f1f2c7f67bd376d6d8bb920ac4b@tecnisys.com.br |
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| Lists: | pgsql-general |
Em 24/10/2023 17:31, Tom Lane escreveu:
> Carlos Alves <carlos(dot)alves(at)tecnisys(dot)com(dot)br> writes:
>
>> I need some help to understand why a transaction wiht a row delete
>> aquire a AccessExclusiveLock and a row update a ExclusiveLock.
>
> UPDATE can use the weaker lock type if it's not modifying any
> column that is part of a unique index. This is to allow concurrency
> with foreign-key checks that might wish to grab a read-only (shared)
> lock on such a tuple.
>
> A DELETE, or an UPDATE that is modifying key columns, has to
> conflict with foreign-key checks.
>
> regards, tom lane
Tom,
thank you very much for your straight to the point answer!
regards
Carlos Alves
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