[postgis-users] Rv: Postgis for Postgres 64 bits

[Darrel Maddy]

"First thing 1000x1000 blocks is too big.  If you are going to be doing a lot of ST_Value calls, you probably want to chunk your tiles to 100x100 or below.

ST_Value currently requires doing a memcopy for each call so the bigger your tiles the more memcopying it will have to do.

On top of that the bigger your tiles, the less useful ST_Intersects is.  Its kind of the same issue with big geometries -- like if you stuffed all of africa in one record, and then were searching for a city in Africa, the ST_Intersects will not be that useful."

Thanks for this. I did do a few tests. This is what I got:

Tile Size	Time
2000		350873ms
1000		235415
500		288298
300		234895	
200		231374

I guess I was concerned that at 200x200 the images were split across 3344 rows as opposed to the 176 of the 1000x1000.  I am learning here, so I will give 100x100 a go (tomorrow) - I just worry about when I need to put the images back together (images will be uploaded as tiles and then the originals - model outputs - will be deleted). The geometry is composed of 100 points (this is for testing only - final configuration has yet to be determined) -  I figured it would be faster if they were all on the same tile, but may be not?

Thanks

Darrel