[postgis-users] On UpdateGeometrySRID() performance

Darafei "Komяpa" Praliaskouski me at komzpa.net
Thu Nov 1 09:51:34 PDT 2018


Please feed in your WKT polygons in EWKT format:


Since every update in Postgres is essentially Delete+Insert, time of
rewriting each and every row being equal to initial Insert time is expected

You can also update SRID in two columns in one go:

update tablename set geom1 = ST_SetSRID(geom1, 4326), geom2 =
ST_SetSRID(geom2, 4326);

Out of curiosity, where did you learn about UpdateGeometrySRID before
learning about ST_SetSRID?

ср, 31 окт. 2018 г. в 21:57, jerry73204 <jerry73204 at gmail.com>:

> Hi all,
> I'm stuck in the low performance of UpdateGeometrySRID().
> I get started with a 50GB polygon dataset in CSV in EPSG:4326
> coordinates. Since I find no way to `\copy` the csv while preserving the
> SRID, the data is imported with null SRID and then `SELECT
> UpdateGeometrySRID('table', 'column', 4326)`.
> The `UpdateGeometrySRID()` takes as long time as that of `\copy`, which
> turns out to be approx two hours. The dataset has two geometry columns
> and thus I have to take triple time to finish this data.
> I profiled the postgresql daemon. The avg disk writing speed is 30MB/s,
> while occasionally peaks to 100MB/s. The SSD, F2FS formatted disk is
> capable of up to 150MB/s. The daemon does not utilize the 4-core
> i5-7600k CPU. It seems to be a single process task with avg CPU load
> 20%, while other workers are idle. I wonder if there's a room for
> improving the performance. Also, I'm looking for if it's possible to
> preserve SRID with `\copy`.
> Jerry Lin
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Darafei Praliaskouski
Support me: http://patreon.com/komzpa
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