On 22/02/10 17:10, River Tarnell wrote:
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Peter Körner:
Has the
table been ANALYZEd since it was imported?
Only if
the osm2pgsql tool did it. It contains a function, pgsql_analyze, for
this, but I'm unsure if it got / when it gets called.
osm_mapnik=# explain analyze select id from planet_osm_ways where pending;
QUERY PLAN
-
--------------------------------------------------------------------------------------------------------------------------------
Seq Scan on planet_osm_ways (cost=0.00..1662990.31 rows=22160666 width=4) (actual
time=496448.422..496448.422 rows=0 loops=1)
Filter: pending
Total runtime: 496448.455 ms
This suggests that the table statistics are very out of date (22m rows
expected vs 0 actual). I suggest ANALYZEing the table and trying the
diff import again.
Osm2PgSql should do an analyze during initial import, though not during diff
imports. From those numbers it looks like (I'd need to check the code) the
analyze was done between the import part and the going over pending ways part,
which would explain the high number of pending ways it expects to see. At the
end of going over pending ways, I presume there shouldn't be any pending ways
left, which is why you would see an actual cost of 0. The diff imports (which
create and then clear pending ways again) are presumably run in a transaction,
so you can't see these with a simple query outside the transaction (which may
well have distorted my testing too) . But a minutely diff shouldn't be close to
22m rows.
It is worth running another analyze though to see if that helps.
Kai
- river.
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