Обсуждение: tsearch2: very slow queries
'k, I'm obviously doing something wrong, since my experiences with sites
like fts.postgresql.org indicate things should be *alot* faster then I'm
getting ...
I have a *very* simple table:
=# \d article_tsearch
Table "public.article_tsearch"
Column | Type | Modifiers
------------+----------+-----------
article_id | integer |
idxft1 | tsvector |
Indexes:
"at_idxft1_idx" gist (idxft1)
rblog=# select count(1) from article_tsearch;
count
--------
643072
(1 row)
rblog=# select count(1) from article_tsearch where idxFT1 @@ to_tsquery('1&dvd');;
count
-------
1681
(1 row)
But, it just seems to take so long to do the query itself:
# explain analyze select * from article_tsearch where idxFT1 @@ to_tsquery('1&dvd') order by rank(idxFT1,
to_tsquery('1&dvd'))desc limit 26;
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=2625.53..2625.60 rows=26 width=36) (actual time=20164.262..20164.597 rows=26 loops=1)
-> Sort (cost=2625.53..2627.14 rows=644 width=36) (actual time=20164.257..20164.298 rows=26 loops=1)
Sort Key: rank(idxft1, '\'1\' & \'dvd\''::tsquery)
-> Index Scan using at_idxft1_idx on article_tsearch (cost=0.00..2595.48 rows=644 width=36) (actual
time=29.476..20153.530rows=1681 loops=1)
Index Cond: (idxft1 @@ '\'1\' & \'dvd\''::tsquery)
Filter: (idxft1 @@ '\'1\' & \'dvd\''::tsquery)
Total runtime: 20166.326 ms
(7 rows)
If it is, then I'm obviously overlooking something key here ... now, I've
read through the docs in contrib/tsearch2/docs, and don't *think* I've
missed anything obvious ... it seems fairly straightforward ...
Is there something else I should be doing to speed the query up any? Or
is this fairly normal?
----
Marc G. Fournier Hub.Org Networking Services (http://www.hub.org)
Email: scrappy@hub.org Yahoo!: yscrappy ICQ: 7615664
Marc G. Fournier wrote: > > 'k, I'm obviously doing something wrong, since my experiences with sites > like fts.postgresql.org indicate things should be *alot* faster then I'm > getting ... Well the first thing I would ask is are you running 8.0? My testing shows that Tsearch is pretty abysmal if you are not running 8.0. At least with very large tables. > > I have a *very* simple table: > > =# \d article_tsearch > Table "public.article_tsearch" > Column | Type | Modifiers > ------------+----------+----------- > article_id | integer | > idxft1 | tsvector | > Indexes: > "at_idxft1_idx" gist (idxft1) > > rblog=# select count(1) from article_tsearch; > count > -------- > 643072 > (1 row) > Is there something else I should be doing to speed the query up any? Or > is this fairly normal? Considering the number of rows I am not that surprised but I would be curious to know what type of HD you have? Also correct me if I am wrong but gist indexes are typically very large. Do you have enough work_mem/sort_mem to keep them from going to disk? Sincerely, Joshua D. Drake > > ---- > Marc G. Fournier Hub.Org Networking Services (http://www.hub.org) > Email: scrappy@hub.org Yahoo!: yscrappy ICQ: 7615664 > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings -- Your PostgreSQL solutions provider, Command Prompt, Inc. 24x7 support - 1.800.492.2240, programming, and consulting Home of PostgreSQL Replicator, plPHP, plPerlNG and pgPHPToolkit http://www.commandprompt.com / http://www.postgresql.org
On Sun, 7 Aug 2005, Joshua D. Drake wrote: > Marc G. Fournier wrote: >> >> 'k, I'm obviously doing something wrong, since my experiences with sites >> like fts.postgresql.org indicate things should be *alot* faster then I'm >> getting ... > > Well the first thing I would ask is are you running 8.0? My testing > shows that Tsearch is pretty abysmal if you are not running 8.0. At > least with very large tables. This is one thing I was fearing, especially with the work that Teodor and gang have been putting into it for 8.1 :( Unfortunately, we're currently stuck with 7.4.6 for this, so that is one thing I'm going to have to take into consideration ... > Considering the number of rows I am not that surprised but I would be > curious to know what type of HD you have? Also correct me if I am wrong > but gist indexes are typically very large. Do you have enough > work_mem/sort_mem to keep them from going to disk? I'm currently playing in a non-production environment (ie. my desktop machine) just to get a feel for things ... our main server for this is a proper 4G of RAM, sort_mem bump'd up quite nicely, and file system spread over multiple spindles ... Right now, I'm just playing with / learning the tsearch stuff, so am more looking at a 'this is the worst case scenario on my box', and this improves things ... not perfect, but anything I can improve here, I know will be easier to improve on the production server :) ---- Marc G. Fournier Hub.Org Networking Services (http://www.hub.org) Email: scrappy@hub.org Yahoo!: yscrappy ICQ: 7615664
Hi there,
tsearch2 is our next problem we plan to attack after we have done with
GiST core. Actually, we did some experiments in background and we're sure we
could very greatly improve tsearch2 performance and add a lot of nice
features. Most probably, we'll call for fund raising for this project
as soon as we find out how to reliably transfer money to us.
Oleg
On Sun, 7 Aug 2005, Marc G. Fournier wrote:
> On Sun, 7 Aug 2005, Joshua D. Drake wrote:
>
>> Marc G. Fournier wrote:
>>>
>>> 'k, I'm obviously doing something wrong, since my experiences with sites
>>> like fts.postgresql.org indicate things should be *alot* faster then I'm
>>> getting ...
>>
>> Well the first thing I would ask is are you running 8.0? My testing shows
>> that Tsearch is pretty abysmal if you are not running 8.0. At least with
>> very large tables.
>
> This is one thing I was fearing, especially with the work that Teodor and
> gang have been putting into it for 8.1 :( Unfortunately, we're currently
> stuck with 7.4.6 for this, so that is one thing I'm going to have to take
> into consideration ...
>
>> Considering the number of rows I am not that surprised but I would be
>> curious to know what type of HD you have? Also correct me if I am wrong but
>> gist indexes are typically very large. Do you have enough work_mem/sort_mem
>> to keep them from going to disk?
>
> I'm currently playing in a non-production environment (ie. my desktop
> machine) just to get a feel for things ... our main server for this is a
> proper 4G of RAM, sort_mem bump'd up quite nicely, and file system spread
> over multiple spindles ...
>
> Right now, I'm just playing with / learning the tsearch stuff, so am more
> looking at a 'this is the worst case scenario on my box', and this improves
> things ... not perfect, but anything I can improve here, I know will be
> easier to improve on the production server :)
>
> ----
> Marc G. Fournier Hub.Org Networking Services (http://www.hub.org)
> Email: scrappy@hub.org Yahoo!: yscrappy ICQ: 7615664
>
> ---------------------------(end of broadcast)---------------------------
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>
> http://www.postgresql.org/docs/faq
>
Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83