[mapserver-users] Highly inefficient MakeValid statement in Mapserver-generated spatial queries

Mon Sep 9 06:05:13 PDT 2019

Hi,

Fortunately not the entire MS4W community is affected, just those who work with MS SQL server.

When makevalid will be turned off MapServer admin will have another option to deal with invalid geometries: select data in  mapfile with IsValid=true. Then the faulty geometries will not show on the map but the whole layer will not fail.

-Jukka Rahkonen-

Lähettäjä: mapserver-users <mapserver-users-bounces at lists.osgeo.org> Puolesta ikeszei at yahoo.com
Lähetetty: maanantai 9. syyskuuta 2019 15.20
Vastaanottaja: 'Seth G' <sethg at geographika.co.uk>; 'Tamas Szekeres' <szekerest at gmail.com>
Kopio: 'MapserverList OSGEO' <mapserver-users at lists.osgeo.org>
Aihe: Re: [mapserver-users] Highly inefficient MakeValid statement in Mapserver-generated spatial queries

Is there any chance that an “unstable” version could be released sooner so that we don’t have to wait another 3-6 months for the next release?
This performance issue affects the entire MS4W user community for all WMS requests. It would be great if an interim version could be released sooner.
Much appreciated,
Istvan

From: Seth G <sethg at geographika.co.uk<mailto:sethg at geographika.co.uk>>
Sent: Sunday, September 8, 2019 11:06 PM
To: Istvan Keszei <ikeszei at yahoo.com<mailto:ikeszei at yahoo.com>>; Tamas Szekeres <szekerest at gmail.com<mailto:szekerest at gmail.com>>
Cc: MapserverList OSGEO <mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>>
Subject: Re: [mapserver-users] Highly inefficient MakeValid statement in Mapserver-generated spatial queries

Hi Istvan,

Unfortunately you won't be able to turn it off without recompiling the MSSQL driver.
I've added a pull request removing these at https://github.com/mapserver/mapserver/pull/5856
This will be merged into master assuming there are no objections.
I assume you are using ms4w as you mention a 4.0.1 release? You'll need to see when a new release of that may be available with the update.
Thanks for reporting this issue,

Seth

--
web:http://geographika.co.uk
twitter: @geographika

On Sun, Sep 8, 2019, at 12:30 AM, Istvan Keszei wrote:

We have real large geospatial tables.  Not having an option to turn MakeValid off will kill our applications’ performance as indexes are essential.

For a simple query, the disk reads are 100x more for a query including the MakeValid. Hence, the cpu resources required are multifold too.

Yes, please turn it off or make it optional. Can this be done manually somehow? We have waited long months for 4.0.1 to come out (with the opacity fix) and now this issue prevents the upgrade.

I see the invalid geometries more of a data maintenance responsibility rather than a query-side-responsibility. I understand for some people this is convenient, so that is why I suggest to make this optional.

Any help is appreciated!

Thank you,
Istvan

On 2019. Sep 7., at 23:55, Tamas Szekeres <szekerest at gmail.com<mailto:szekerest at gmail.com>> wrote:
I think we can remove MakeValid from the queries entirely.
The problem is that if the table contains invalid geometries, the entire query will fail.

Best regards,

Tamas

Seth G <sethg at geographika.co.uk<mailto:sethg at geographika.co.uk>> ezt írta (időpont: 2019. szept. 7., Szo, 21:35):

Hi,

Good question. This is a fairly new change as part of https://github.com/mapserver/mapserver/issues/5781 from April this year.
In SQL Profiler I seem to get GEOM.STIntersects for WFS requests and GEOM.MakeVaid().STIntersects for WMS.
MakeValid does appear to stop the index being used. Do you have a link which says this definitively?

Seth

--
web:http://geographika.co.uk
twitter: @geographika

On Sat, Sep 7, 2019, at 12:02 PM, ikeszei at yahoo.com<mailto:ikeszei at yahoo.com> wrote:

Hello,

I noticed that when MapServer issues the query to MS SQL Server, it appends a .MakeValid() tag to the geometry field, which makes data access highly inefficient as no spatial indexes can be used when the MakeValid() is used. Here is the query that is being produced:

SELECT

convert(nvarchar(max), [label]),

[ogr_geometry],

convert(varchar(36), [ogr_fid])

FROM

section

WHERE

ogr_geometry.MakeValid().STIntersects(geometry::STGeomFromText('POLYGON((-10973271.1167343 5605636.0681215,-10963019.0003155 5605636.0681215,-10963019.0003155 5614459.76757417,-10973271.1167343 5614459.76757417,-10973271.1167343 5605636.0681215))',3857)) = 1

Here is the data access string from the map file:

DATA "ogr_geometry from section USING UNIQUE ogr_fid USING SRID=3857"

Earlier I was using a specific HINT for index usage:

DATA "ogr_geometry from section WITH (INDEX(section_ogr_geometry_idx)) USING UNIQUE ogr_fid USING SRID=3857"

But since MapServer adds the MakeValid automatically, I am getting the following error:

Msg 8635, Level 16, State 9, Line 1

The query processor could not produce a query plan for a query with a spatial index hint.  Reason: Could not find required binary spatial method in a condition.  Try removing the index hints or removing SET FORCEPLAN.

How do I configure mapserver to NOT ADD the MakeValid to every single one of its queries ?

Any response is much appreciated !

Thanks,

Istvan

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