Tom Lane wrote:
> Bruce Momjian <[EMAIL PROTECTED]> writes:
> > I remember three problems: build time, index size, and concurrency
> > problems. I was wondering about the equal key case myself, and assumed
> > hash may be a win there, but with the concurrency problems, is that even
> > possible?
>
> Sure. Many-equal-keys are a problem for btree whether you have any
> concurrency or not.
>
> > OK, I have reworded it. Is that better?
>
> It's better, but you've still discarded the original's explicit mention
> of concurrency problems. Why do you want to remove information?
OK, concurrency added. How is that?
>
> > How about an elog(NOTICE) for hash use?
>
> I don't think that's appropriate.
I was thinking of this during CREATE INDEX ... hash:
NOTICE: Hash index use is discouraged. See the CREATE INDEX
reference page for more information.
Does anyone else like/dislike that?
--
Bruce Momjian | http://candle.pha.pa.us
[EMAIL PROTECTED] | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
Index: doc/src/sgml/indices.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/indices.sgml,v
retrieving revision 1.32
diff -c -r1.32 indices.sgml
*** doc/src/sgml/indices.sgml 21 Jun 2002 03:25:53 -0000 1.32
--- doc/src/sgml/indices.sgml 21 Jun 2002 16:50:23 -0000
***************
*** 181,189 ****
</synopsis>
<note>
<para>
! Testing has shown that hash indexes are slower than btree indexes,
! and the size and build time for hash indexes is much worse. For
! these reasons, hash index use is discouraged.
</para>
</note>
</para>
--- 181,190 ----
</synopsis>
<note>
<para>
! Testing has shown hash indexes to be similar or slower than btree
! indexes, and the index size and build time for hash indexes is much
! worse. Hash indexes also suffer poor performance under high
! concurrency. For these reasons, hash index use is discouraged.
</para>
</note>
</para>
Index: doc/src/sgml/ref/create_index.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v
retrieving revision 1.32
diff -c -r1.32 create_index.sgml
*** doc/src/sgml/ref/create_index.sgml 21 Jun 2002 03:25:53 -0000 1.32
--- doc/src/sgml/ref/create_index.sgml 21 Jun 2002 16:50:23 -0000
***************
*** 330,338 ****
the <literal>=</literal> operator.
</para>
<para>
! Testing has shown that hash indexes are slower than btree indexes,
! and the size and build time for hash indexes is much worse. For
! these reasons, hash index use is discouraged.
</para>
<para>
--- 330,339 ----
the <literal>=</literal> operator.
</para>
<para>
! Testing has shown hash indexes to be similar or slower than btree
! indexes, and the index size and build time for hash indexes is much
! worse. Hash indexes also suffer poor performance under high
! concurrency. For these reasons, hash index use is discouraged.
</para>
<para>
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