Steve, Any chance you could share your data with the developers? this is a very strange result.
P On Fri, Jun 6, 2008 at 9:37 AM, Steve Kondik <[EMAIL PROTECTED]> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Steve Kondik wrote: >> Mark Cave-Ayland wrote: >>> Steve Kondik wrote: >>>> -----BEGIN PGP SIGNED MESSAGE----- >>>> Hash: SHA1 >>>> >>>> I'm seeing this same kind of slowness. I am in the process of migrating >>>> an application from Oracle to Postgres. One query that seems to take >>>> longer than it should is a very simple point-in-bbox query which takes 3 >>>> seconds. There are 32000 rows in the table, and the query is as simple >>>> as it can be: >>>> >>>> select count(*) from geography where type='Z' and centroid && (select >>>> geometry from geography where id=69495); >>>> >>>> The second geography is the USA, so this query gets all zipcodes inside >>>> the bbox, using precalculated centroids. The query plan looks fine as >>>> well: >>>> >>>> Aggregate (cost=16.56..16.57 rows=1 width=0) (actual >>>> time=2407.123..2407.125 rows=1 loops=1) >>>> InitPlan >>>> -> Index Scan using geography_pkey on geography (cost=0.00..8.28 >>>> rows=1 width=4528) (actual time=0.027..0.030 rows=1 loops=1) >>>> Index Cond: (id = 69495) >>>> -> Index Scan using idx_geography_centroid_z on geography >>>> (cost=0.00..8.28 rows=1 width=0) (actual time=1.417..2355.049 rows=29687 >>>> loops=1) >>>> Index Cond: (centroid && $0) >>>> Filter: (centroid && $0) >>>> Total runtime: 2407.194 ms >>>> (8 rows) >>>> >>>> >>>> Any thoughts? This query takes 200ms on Oracle. It seems like >>>> something is wrong for it to take 3 seconds on PostGIS. It's faster for >>>> smaller geometries (like a state), but I don't understand why since its >>>> just point-inside-bbox. >> >>> Hi Steve, >> >>> Well from the above you can see fairly easily that the time is >>> disappearing into the second index scan. The above output doesn't look >>> quite right somehow (it's missing at least one node indicator) - can you >>> try cutting and pasting the exact output from EXPLAIN into an email >>> again? Also we'll need the output of "\d geography" from within psql. >> >> >>> ATB, >> >>> Mark. >> >> >> >> Sure thing. It's taking quite a bit longer now because we're doing some >> bulk loading. When nothing else is running, the query takes about 4 >> seconds. >> >> >> health_central_22=> explain analyze select count(*) from geography where >> type='Z' and centroid && (select geometry from geography where id=69495); >> >> QUERY PLAN >> >> - >> --------------------------------------------------------------------------------------------------------------------------------------------------- >> Aggregate (cost=16.56..16.57 rows=1 width=0) (actual >> time=16534.739..16534.741 rows=1 loops=1) >> InitPlan >> -> Index Scan using geography_pkey on geography (cost=0.00..8.28 >> rows=1 width=4528) (actual time=0.076..0.080 rows=1 loops=1) >> Index Cond: (id = 69495) >> -> Index Scan using idx_geography_centroid_z on geography >> (cost=0.00..8.28 rows=1 width=0) (actual time=25.453..16192.427 >> rows=29687 loops=1) >> Index Cond: (centroid && $0) >> Filter: (centroid && $0) >> Total runtime: 16534.809 ms >> (8 rows) >> >> health_central_22=> \d geography >> Table "public.geography" >> Column | Type | Modifiers >> --------------+------------------------+----------- >> type | character(1) | not null >> id | bigint | not null >> centroid | geometry | >> geometry | geometry | >> name | character varying(32) | not null >> population | bigint | >> abbreviation | character varying(2) | >> po_name | character varying(100) | >> id_geo_state | bigint | >> Indexes: >> "geography_pkey" PRIMARY KEY, btree (id) >> "idx_geography_2" btree (name) >> "idx_geography_3" btree (abbreviation) >> "idx_geography_4" btree (id_geo_state) >> "idx_geography_centroid" gist (centroid) >> "idx_geography_centroid_c" gist (centroid) WHERE type = 'C'::bpchar >> "idx_geography_centroid_s" gist (centroid) WHERE type = 'S'::bpchar >> "idx_geography_centroid_z" gist (centroid) WHERE type = 'Z'::bpchar >> "idx_geography_geometry" gist (geometry) CLUSTER >> "idx_geography_geometry_c" gist (geometry) WHERE type = 'C'::bpchar >> "idx_geography_geometry_r" gist (geometry) WHERE type = 'R'::bpchar >> "idx_geography_geometry_s" gist (geometry) WHERE type = 'S'::bpchar >> "idx_geography_geometry_z" gist (geometry) WHERE type = 'Z'::bpchar >> Foreign-key constraints: >> "fk_geography_1" FOREIGN KEY (id_geo_state) REFERENCES geography(id) >> > > Adding force_2d speeds this up immensely. Not sure I understand why > this is necessary, but I'm still getting used to PostGIS. > > > health_central_22=> explain analyze select id,name from geography where > type='Z' and centroid && (select force_2d(geometry) from geography where > id=69495); > QUERY > PLAN > - > ------------------------------------------------------------------------------------------------------------------------------------------ > Index Scan using idx_geography_centroid on geography (cost=8.29..16.57 > rows=1 width=14) (actual time=0.263..125.338 rows=29687 loops=1) > Index Cond: (centroid && $0) > Filter: ((centroid && $0) AND (type = 'Z'::bpchar)) > InitPlan > -> Index Scan using geography_pkey on geography (cost=0.00..8.29 > rows=1 width=4441) (actual time=0.158..0.161 rows=1 loops=1) > Index Cond: (id = 69495) > Total runtime: 171.229 ms > (7 rows) > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.6 (GNU/Linux) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org > > iD8DBQFISWe8MrBfzfMVwMcRAkUBAJ9uLeK7kLotz6+CUuKd2Tg5pNj2XwCeLVXV > RlUY5e2Dwyx1EWa3ln0Ky6M= > =B0/W > -----END PGP SIGNATURE----- > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
