David,
my guess without studying the code is that this does not make a
difference in performance.
I think a Mapserver EXPRESSION will make it into the SQL that OGR passes
to MySQL in the end. I don't believe Mapserver does the filtering itself
on the whole dataset.
Best regards,
Bart
Fawcett, David schreef:
Bart,
I am assuming that this method would be faster than requesting the whole
table from MySQL and then using variable substitution to set an
expression for a class that displays only the record of interest.
I know that it would be faster to only pass the data that is needed, I
am more curious about whether the OGR/MySQL query mechanism is better or
worse than 'filtering' with a mapfile expression.
David.
-----Original Message-----
From: UMN MapServer Users List [mailto:[EMAIL PROTECTED] On
Behalf Of Bart van den Eijnden (OSGIS)
Sent: Tuesday, September 19, 2006 2:31 AM
To: [email protected]
Subject: Re: [UMN_MAPSERVER-USERS] How can Create OVF file (for OGR
MYSQL connection) interactively
See:
http://mapserver.gis.umn.edu/cgi-bin/wiki.pl?VirtualSpatialData
Section: Dynamic Control of Virtual Sources
Best regards,
Bart
Dear friends;
Finally I have solved to read point data form mysql database than
draw map by using those data.
I have created Peak Ground Acceleration (PGA) map for the specified
earthquake which data are
stored in MySql. But I would like to display map for all earthquake
which
are
described in the Mysql table as eq-id column.I mean PGA data are
stored
in mysql database.table for several earthquakes
and one of the column is called EQ_ID which use for the seperate PGA
data
from other earthquake like
EQ_ID Lon Lat PGA
200006060242 30.40 32.45 2.5
200006060242 30.41 32.46 2.6
200006060242 30.42 32.47 2.7
...
200606071708 38.45 40.98 5.6
200606071708 38.46 40.99 5.7
200606071708 38.47 41.00 5.7
200606071708 38.48 41.01 5.8
.
.
.
I have querid mysql database by using ovf file as following
<OGRVRTDataSource>
<OGRVRTLayer name="acceleration">
<SrcDataSource>MYSQL:database,user=user,password=pass_wd,host=100.00.00.
21,port=3306,tables=d_pgadata1</SrcDataSource>
<SrcSQL>SELECT eq_id,latitude,longitude,acceleration from d_pgadata1
where eq_id like '%200006060242%' </SrcSQL>
<GeometryType>wkbPoint</GeometryType>
<GeometryField encoding="PointFromColumns" x="longitude"
y="latitude"/>
</OGRVRTLayer>
</OGRVRTDataSource>
As you see when I create map by layer OGR this will just the eq_id
like '%200006060242%'. But I would like to change this eq_id by
interactively for example who will
like to see 200606071708 earthquake PGA map he/she can change sql
statement in
ovf file by using php or html commands from web...
Do you have any idea is it possible or not.
Please I wellcome any kind of information about it..
Thank you
Murat
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Bart van den Eijnden
OSGIS, Open Source GIS
http://www.osgis.nl
