| From: | Greg Stark <gsstark(at)mit(dot)edu> |
|---|---|
| To: | Gaetano Mendola <mendola(at)bigfoot(dot)com> |
| Cc: | Dennis Bjorklund <db(at)zigo(dot)dhs(dot)org>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: 7.4 vs 7.3 ( hash join issue ) |
| Date: | 2004-09-22 13:43:24 |
| Message-ID: | 87y8j2ctc3.fsf@stark.xeocode.com |
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| Lists: | pgsql-patches pgsql-performance |
Gaetano Mendola <mendola(at)bigfoot(dot)com> writes:
> hash_join = on
> -> Seq Scan on lookup_tipo_evento le (cost=0.00..1.16 rows=16 width=32) (actual time=0.017..0.038 rows=16 loops=1)
>
> hash_join = off
> -> Seq Scan on lookup_tipo_evento le (cost=0.00..1.16 rows=16 width=32) (never executed)
Actually this looks like it's arguably a bug to me. Why does the hash join
execute the sequential scan at all? Shouldn't it also like the merge join
recognize that the other hashed relation is empty and skip the sequential scan
entirely?
--
greg
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