Thanks René-Luc and Kimaidou,
This sounds like a useful fix. I will test and report if I run into issues.
Do you have any numbers/observations how much this will speed up
services that use Postgis as storage? I mean very rough numbers only.
Anyway - I will test.
Andreas
On 16.09.2015 10:19, kimaidou wrote:
Hi all
René-Luc has found why this appeared, essentially with Lizmap. Lizmap
send GetMap request to QGIS Server with a non empty STYLES parameter
(ex: STYLES=default). This is to let the user choose the style.
In this case, QGIS Server did not use the maplayer cache, so it had to
get all information from the provider to build the maplayer objet for
each GETMAP request ! This is why in this case, a new opening was made
on the file.
The following commit fixes it :
https://github.com/qgis/QGIS/commit/a5450a78ffcbba9a75afa8be43460ad741fea050
It has been backported in branches release-2_8 and release-2_10
A very good side effect is with PostGIS layers :
* before, QGIS Server sent many many queries to build the whole
maplayer for each GetMAP, such as : [1] if metadata were available,
and worse like [2] if metadata were not (for example for PostGIS views
or if the user had disabled "use metadata" )
* now only the main "get data" queries are sent for each GetMap, like [3]
In [2], you can see some performance kiling queries (on big datasets),
such as
SELECT count(distinct ""nb"")=count(""nb"") FROM (SELECT row_number()
OVER() AS nb, * FROM ""2013"".v_geo_parcelle
) AS ""subQuery_0"""
SELECT st_extent(""geom"") FROM (SELECT row_number() OVER() AS nb, *
FROM ""2013"".v_geo_parcelle
) AS ""subQuery_0""
[1] https://paste.sh/yguqyRWL#EPcHHVH3uuijGgEtzH0pAlHb
[2] https://paste.sh/frCglZ9A#A1nQ6BXtdBeEiZWQmTJP8v9l
[3] https://paste.sh/Rkvqf757#K1MCRitovIxMblBVils1VF7r
Thanks a lot to René-Luc for fixing this !
Cheers
Michaël
2015-09-14 8:39 GMT+02:00 Luca Manganelli <[email protected]
<mailto:[email protected]>>:
On Fri, Sep 11, 2015 at 5:09 PM, kimaidou <[email protected]
<mailto:[email protected]>> wrote:
> I tested a quick and dirty patch, by replacing all occurences of
OGROpen byt
> OGROpenShared in QGIS source, then rebuild and test server side
--> No locks
> anymore ! QGIS Server works like a charm here, without
increasing the number
> ...
This is a great fix! It's important to optimize resources, expecially
with qgis server.
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