[postgis] Gut feeling question about performance

Petri J. Riipinen petri.riipinen at nic.fi
Wed Oct 24 11:36:52 PDT 2001

Hi folks,

I'm putting a big road network (about 3 million records, each representing 
a single ARC-shape) into PostgreSQL + PostGIS. This covers roughly 600x1500 
km area in real world. I'm planning on making a GiST index for this table. 
The data is originally in ESRI Shapefile-format and I have converted it to 
SQL with the shp2pgsql-program.

My main access need is to get any 1x1 (or 2x2) km block from the whole 
area. That is the window size that is shown to the user in my application 
that will act as a client to the PostgreSQL via libpq. That viewarea 
contains less than 500 shapes, i.e. records returned from the query.

The computer running the app will be a PC with 300MHz CPU and 128M of RAM. 
The main road network table (+ GiST index) will be only built once in my 
development PC (fortunately a 1.7G P4 w 512M RAM) and I will only read the 
table at runtime, never modify it in anyway.

Now, what is your gut feeling people, how fast query responses can I 
expect? Will I get a response under one second? The application should have 
a reasonable response time when user changes the window location, so 1 sec 
is pretty much the top that I can stand.

Any tips that I should know when optimising the query performance...?

- Petri

PS. I have a possibility (though undesirable) of increasing the CPU speed, 
but not really the RAM.
PPS. Note that I only need very optimized query speed, the insertion of 
data in beginning can take as much time as needed, I'll only do it once anyway.
   Petri J. Riipinen
petri.riipinen at nic.fi

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