| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | srn(at)commsecure(dot)com(dot)au |
| Cc: | pgsql-general(at)postgresql(dot)org, Mark Greenaway <mark(at)commsecure(dot)com(dot)au> |
| Subject: | Re: USING HASH considered harmful? |
| Date: | 2001-08-17 01:59:02 |
| Message-ID: | 200108170159.f7H1x2919714@candle.pha.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
Checking application/pgp-signature: FAILURE
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> 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
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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