[UMN_MAPSERVER-USERS] performance with different data formats

[Mark Adams]

Hi All,   I’m looking for ideas and explanations regarding performance when publishing maps from ArcSDE and Oracle Spatial, and also with displaying attribute data from these data source. We have been working for a while now with from these formats through MapServer and PHP mapscript, and have found the performance has been disappointing. Specifically, we are trying to use Oracle Spatial (9i) as well as ArcSDE against both Oracle and SQL Server (we gave up entirely on MS Access personal geodatabase through OGR). Generally speaking we’ve found that map draw operations are substantially slower with these data sources than if we use Shapefiles; and that the performance hit is even greater with drawquery operations, especially as the size of the selected feature sets increases.   We did some informal testing, both within our MapServer environment to compare the performance with different data formats, and also between MapServer and ESRI ArcIMS environments. Here are some of the results we came up with:   1. We compared MapServer performance with SQL Server ArcSDE and Shapefiles (with spatial indexes defined for the Shapefiles), with a large polygon layer representing property parcels (329870 records). To draw the whole layer at full extents, it took 10 seconds with Shapefiles, 26 with SDE. To zoom in to a small area, 0.3 seconds with Shapefiles, 2.2 seconds with SDE. These times are just the draw times reported from the debugging. 2. We compared MapServer performance with Oracle Spatial 9i Standard Edition and Shapefiles, using a polygon layer that has about 6000 records. To draw the whole layer at full extents, it took 0.29 seconds with Shapefiles, 0.98 with Spatial. To zoom in to a small area, 0.28 seconds with Shapefiles, 0.6 seconds with Spatial. We also tested selected and highlighting features: select 75 records (querybyrect), 0.5 seconds with Shape, 2.7 with Spatial; select 3000 records, 0.5 seconds with Shape, 9.4 with Spatial. 3. We compared MapServer performance with ArcIMS performance using the same data sources (the property parcel layer with 329870 records). This is an even more informal test as we didn’t have access to the same debugging info on the ArcIMS side, so I will just say that comparing with Shapefiles only, the 2 platforms were roughly comparable; but ArcIMS speeds up a little with SDE, while MapServer slows dramatically with this format. 4. We have even more problems when we want to use the results from the selection in test 2 to show the attribute data to the user on a separate HTML form. On the ArcIMS side we can process attribute data quick quickly as the server sends back an XML file with the attribute data in it. On the MapServer side the only way we know to publish the attributes is to loop through each field of each returned record to create the HTML table. Extracting the data in this fashion is again, for some reason, way faster with Shapefiles as the selection sets get bigger – for example with the 3000 record test it took 3.2 seconds for Shapefiles, and 9.4 seconds with Oracle Spatial. When you add those times to the draw times the Oracle Spatial approach becomes unworkable; likewise with ArcSDE.   So, there are some questions in all this that I’m hoping the experts on the list can answer: are we doing something wrong, or are these numbers to be expected, and if the latter, why are these other, supposedly enterprise type data sources so slow? Is there a better way to get the attributes onto a form than looping through each record, each field? Are there steps we can take to optimize the performance of Spatial or SDE with MapServer?   I know there are lots of other users out there using Spatial and SDE – I’d really appreciate hearing what has worked for you.   Finally, anticipating questions on the testing technique, I do want to stress the use of the term “informal” to describe these tests – this was not a formal benchmarking exercise. But the results bear out the experiences we’ve been having over months of working with these datasets, so while the precise times are not to be taken too seriously I think the general results are representative.   Thanks in advance.     ------------------------------ Mark Adams General Manager, Ottawa Office DPRA Canada 440 Laurier Ave W Suite 200 Ottawa, ON K1R 7X6 Phone: 613.782.2326 Fax: 613.782.2228 Email: [EMAIL PROTECTED]