On Fri, 12 Sep 2008, Dmitry Koterov wrote:
Hello.
TSearch2 allows to search a table of tsvectors by a single tsquery.
I need to solve the reverse problem.
*I have a large table of tsquery. I need to find all tsqueries in that table
that match a single document tsvector:
*
CREATE TABLE "test"."test_tsq" (
"id" SERIAL,
"q" TSQUERY NOT NULL,
CONSTRAINT "test_tsq_pkey" PRIMARY KEY("id")
);
insert into test.test_tsq(q)
select to_tsquery(g || 'x' || g) from generate_series(100000, 900000) as g;
explain analyze
select * from test.test_tsq
where to_tsvector('400000x400000') @@ q
why do you need tsvector @@ q ? Much better to use tsquery = tsquery
test=# explain analyze select * from test_tsq where q = '400000x400000'::tsque>
QUERY PLAN
-----------------------------------------------------------------------------------------------------------
Seq Scan on test_tsq (cost=0.00..16667.01 rows=1 width=38) (actual time=129.208..341.111 rows=1 loops=1)
Filter: (q = '''400000x400000'''::tsquery)
Total runtime: 341.134 ms
(3 rows)
Time: 341.478 ms
This gets a strange explain analyze:
QUERY PLAN
Seq Scan on test_tsq (cost=0.00..17477.01 rows=800 width=36) (actual
time=68.698..181.458 rows=1 loops=1)
Filter: ('''400000x400000'':1'::tsvector @@ q)
Total runtime: 181.484 ms
No matter if I use GIST index on test_tsq.q or not: the explain analyze
result is the same.
So, why "rows=800"? The table contains much more rows...
'800' is the number of estimated rows, which is not good, since you got only
1 row.
Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@xxxxxxxxxx, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83
