query slowdown after 9.0 -> 9.4 migration

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От Filip Rembiałkowski
Тема query slowdown after 9.0 -> 9.4 migration
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Msg-id CAP_rwwn6AqwfCDsmpzVaoZd_6FSu7RFECqqfUPGf2n9uv+VVuA@mail.gmail.com
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Ответы Re: query slowdown after 9.0 -> 9.4 migration  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
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Hi.

Query run time degraded after migration from Pg 9.0 + postgis 1.5 to Pg 9.4 + postgis 2.2.

1 ms versus 7 ms.

Same query, same data, same schema, similar hardware. Data is small and fits in cache.

EXPLAIN shows heap scan cost increase. What can be the reason for 40-fold increase in page scans needed to run Bitmap Heap Scan with Filter and Recheck?

GIST index performance looks OK.


PostgreSQL 9.0.23 on x86_64-suse-linux-gnu, compiled by GCC gcc (SUSE Linux) 4.8.3 20140627 [gcc-4_8-branch revision 212064], 64-bit
POSTGIS="1.5.4" GEOS="3.4.2-CAPI-1.8.2 r3921" PROJ="Rel. 4.8.0, 6 March 2012" LIBXML="2.7.8" USE_STATS (procs from 1.5 r5976 need upgrade)
-> https://explain.depesz.com/s/C3Vw

PostgreSQL 9.4.7 on x86_64-suse-linux-gnu, compiled by gcc (SUSE Linux) 4.8.5, 64-bit
POSTGIS="2.2.2 r14797" GEOS="3.5.0-CAPI-1.9.0 r4084" PROJ="Rel. 4.9.2, 08 September 2015" GDAL="GDAL 2.1.0, released 2016/04/25 GDAL_DATA not found" LIBXML="2.9.1" LIBJSON="0.12" (core procs from "2.2.1 r14555" need upgrade) TOPOLOGY (topology procs from "2.2.1 r14555" need upgrade) RASTER (raster procs from "2.2.1 r14555" need upgrade)
-> https://explain.depesz.com/s/24GA


Query:

SELECT round(meters_to_miles(st_distance_sphere(ST_GeomFromText('POINT(-77.0364 38.89524)', 4326),llpoint))::numeric,2) as _distance FROM storelocator WHERE st_expand(ST_GeomFromText('POINT(-77.0364 38.89524)', 4326), miles_to_degree(50,38.89524)) && llpoint AND st_distance_sphere(ST_GeomFromText('POINT(-77.0364 38.89524)', 4326), llpoint) <= miles_to_meters(50) ORDER BY _distance LIMIT 10;



thanks for any suggestions / ideas.



Filip


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