[postgis-users] [postgis] Optimal tile size for Raster

[Heng Zhi Feng (zheng@hsr.ch)]

Hello,

I am having to import Raster (.tiff) into Postgres using the raster2pgsql tool. The raster used is 12MB in size and the Postgres version is 9.1 on Ubuntu 13.10.

The virtual machine has the following hardware specs.

-          17408 Memory

-          4 Processors

-          16GB HDD
The command used to import (with the parameters) is: raster2pgsql -s 4326 -I -C -M -R -d -l 4 U:\Desktop\ilatlon_float.tif -F -t 8x8 ilatlon8x8|psql -d Raster
And the tile size varies from 8x8 all the way up till 2048 (power of 2s).

My results from the query ran showed that with larger tile size, the query has a faster returned timing.
This trend is however opposite to some of the similar tests conducted by others (from the internet), where their conclusion was smaller tile size will have better performance.

This is my one of the query I ran:
EXPLAIN (ANALYZE,BUFFERS)
SELECT DISTINCT ST_Intersection(r.rast::geometry,q.rast::geometry)
FROM ilatlon32x32 as r, boundedilatlon32x32 as q;

Is someone able to give advice on this, if this result that I obtained was legit? Or suggest where could the problem be that gave this result?

Regards,
Zhi Feng
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