Re: DELETE versus TRUNCATE during pg_dump.... - Mailing list pgsql-general

From Patrick Hatcher
Subject Re: DELETE versus TRUNCATE during pg_dump....
Date
Msg-id 41C8EBA1.1060306@comcast.net
Whole thread Raw
In response to Re: DELETE versus TRUNCATE during pg_dump....  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
Hey there Tom thanks for the answer.

However, as you saw I wrote this early in the morning and forgot an
important piece of information:
The table at the time of the truncate was not being dumped.  I could see
in pg_stat_activity that it was chugging away at one of the 63M row
tables I have.

Does this make a difference?

Tom Lane wrote:

>Patrick Hatcher <pathat@comcast.net> writes:
>
>
>>Curious:  Why would a DELETE FROM tablename work while a pg_dump is
>>occurring but a TRUNCATE tablename will stay in a lock state until the
>>pg_dump is complete?
>>
>>
>
>TRUNCATE requires an exclusive lock on the table.
>
>This is pretty much a no-free-lunch situation: if you want the pg_dump
>to be able to dump all the rows that existed when it started, you can
>hardly expect to be able to physically remove those rows meanwhile.
>
>            regards, tom lane
>
>
>

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