Andreas Joseph Krogh wrote:
nbeweb=> EXPLAIN select count(*) from onp_web_index;
QUERY PLAN
-----------------------------------------------------------------------------
Hi all.
I have a problem with a table which only has 298 rows in it. A select count(*)
takes forever and CTRL-C also takes a long time canceling the query. There
are only 298 rows in the table when count(*) returns. How come it takes such
a long time counting only 298 rows? Here is EXPLAIN ANALYZE:
nbeweb=> EXPLAIN ANALYZE select count(*) from onp_web_index;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------
Aggregate (cost=205759.52..205759.52 rows=1 width=0) (actual
time=179748.910..179748.913 rows=1 loops=1)
-> Seq Scan on onp_web_index (cost=0.00..205455.41 rows=121641 width=0)
(actual time=179735.956..179747.821 rows=298 loops=1)
Total runtime: 179748.993 ms
Why does PG think you have 121641 rows in this table?
How often do you vacuum it?
How often do you analyse it?
Does "vacuum full verbose" show a lot of dead rows being removed?
I'm suspecting a *lot* of dead rows need to be removed.
--
Richard Huxton
Archonet Ltd
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