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Message-ID: <34d269d40809091823t204e252fl246443be71aed9ff@mail.gmail.com>
Date: Tue, 9 Sep 2008 19:23:03 -0600
From: "Alex Hunsaker" <badalex@gmail.com>
To: "Kenneth Marshall" <ktm@rice.edu>
Subject: Re: hash index improving v3
Cc: "Tom Lane" <tgl@sss.pgh.pa.us>, "Xiao Meng" <mx.cogito@gmail.com>,
	"Zdenek Kotala" <Zdenek.Kotala@sun.com>, pgsql-patches@postgresql.org,
	"Jonah H. Harris" <jonah.harris@gmail.com>
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On Tue, Sep 9, 2008 at 7:48 AM, Kenneth Marshall <ktm@rice.edu> wrote:
> I think that the glacial speed for generating a big hash index is
> the same problem that the original code faced.

Yeah sorry, I was not saying it was a new problem with the patch.  Err
at least not trying to :) *Both* of them had been running at 18+ (I
finally killed them sometime Sunday or around +32 hours...)

> It would be useful to have an equivalent test for the hash-only
> index without the modified int8 hash function, since that would
> be more representative of its performance. The collision rates
> that I was observing in my tests of the old and new mix() functions
> was about 2 * (1/10000) of what you test generated. You could just
> test against the integers between 1 and 2000000.

Sure but then its pretty much just a general test of patch vs no
patch.  i.e. How do we measure how much longer collisions take when
the new patch makes things faster?  That's what I was trying to
measure... Though I apologize I don't think that was clearly stated
anywhere...
Now of course it still would be interesting...  And if its only to
2,000,000 I can still use the modified int8 or just use the int4
one...

Anyway Here are the numbers:
create table test_hash(num int8);
insert into test_hash (num) select generate_series(1, 2000000);
create index test_hash_num_idx on test_hash (num);

pgbench -c1 -n -t10000 -f bench_index.sql
cvs head: tps = 3161.500511
v5:           tps = 7248.808839

BTW Im still planning on doing a wide vs narrow test... sometime... :)