Re: USING HASH considered harmful?

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От Bruce Momjian
Тема Re: USING HASH considered harmful?
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Msg-id 200108170159.f7H1x2919714@candle.pha.pa.us
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Ответ на USING HASH considered harmful?  (Stephen Robert Norris <srn@commsecure.com.au>)
Ответы Re: USING HASH considered harmful?  (Stephen Robert Norris <srn@commsecure.com.au>)
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Checking application/pgp-signature: FAILURE
-- Start of PGP signed section.
> We've just discovered a rather nasty feature of hashes, namely that
> simultaneous reads & writes to a single row will deadlock if there
> is a hash index on the table.
>
> I guess this is because PG really has to lock the hash table entry in
> both cases. It does, however, make HASH indices completely useless for
> any table that you might want to update.
>
> Is this a known feature?

Yes, I have heard about this problem.  Would you test btree vs hash and
report back which is faster.  I have requested this from >20 people and
no one reported back.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
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