Re: VACUUM ANALYZE blocking both reads and writes to a table

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От Tom Lane
Тема Re: VACUUM ANALYZE blocking both reads and writes to a table
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Msg-id 3064.1214852440@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: VACUUM ANALYZE blocking both reads and writes to a table  (Alvaro Herrera)
Ответы Re: VACUUM ANALYZE blocking both reads and writes to a table  (Alvaro Herrera)
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VACUUM ANALYZE blocking both reads and writes to a table  (Peter Schuller, )
 Re: VACUUM ANALYZE blocking both reads and writes to a table  (Alvaro Herrera, )
  Re: VACUUM ANALYZE blocking both reads and writes to a table  (Peter Schuller, )
  Re: VACUUM ANALYZE blocking both reads and writes to a table  (Peter Schuller, )
   Re: VACUUM ANALYZE blocking both reads and writes to a table  (Alvaro Herrera, )
    Re: VACUUM ANALYZE blocking both reads and writes to a table  (Tom Lane, )
     Re: VACUUM ANALYZE blocking both reads and writes to a table  (Alvaro Herrera, )
      Re: VACUUM ANALYZE blocking both reads and writes to a table  (Peter Schuller, )
    Re: VACUUM ANALYZE blocking both reads and writes to a table  (Alvaro Herrera, )
Alvaro Herrera <> writes:
> Peter Schuller wrote:
>> Even with the fix the lock is held. Is the operation expected to be
>> "fast" (for some definition of "fast") and in-memory, or is this
>> something that causes significant disk I/O and/or scales badly with
>> table size or similar?

> It is fast.

Well, it's *normally* fast.  In a situation where there are a whole lot
of empty pages at the end of the table, it could be slow.  That's
probably not very likely on a heavily used table.  One should also note
that

(1) The only way vacuum will be able to obtain an exclusive lock in the
first place is if there are *no* other transactions using the table at
the time.

(2) If it's autovacuum we're talking about, it will get kicked off the
table if anyone else comes along and wants a conflicting lock.

            regards, tom lane

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