Why am I Observing Poor Geospatial Query Performance?

Question

Our HANA Rev. 72 Amazon instance is performing very poorly when selecting geospatial polygons from tables.  I'm hoping someone out there knows why.
Here's one example.  The table below has just 51 records; one for each state (includingPuerto Rico). The table has a GEOMETRY column that contains a polygon outline of the state.
The query below uses ST_Covers() to find the state at a given latitude, longitude. It takes more than 9 seconds to execute!
SELECT  STATE_NAME, STATE_FIPS as STATE_ID, SHAPE.ST_AsGeoJSON() as STATE_POLYGON
from GEO_SHAPES.US_STATES where SHAPE.ST_Covers(new ST_Point('POINT(-105.123 39.456)')) = 1
Statement 'SELECT STATE_NAME, STATE_FIPS as STATE_ID, SHAPE.ST_AsGeoJSON() as STATE_POLYGON from ...'  successfully executed in 9.326 seconds  (server processing time: 8.629 seconds)
Essentially all the time goes into the SHAPE.ST_Covers() function.  The same query without this function runs in 6 ms.
Does anybody have any idea why?

Answer 1

JeffKasper wrote:
So I have been running activity monitor and what I am seeing is 40 MB of "Free" RAM with 630 MB "Wired", 2.5 GB "Inactive" and about 5 GB of "Active".
Both "Free" and "Inactive" are (supposed to be) available for use by any process that wants it.
When you first start up, most memory is, of course, "Free." As apps or system processes need memory, that's where OSX gets it. When they release it, however, it does not go back to Free, but to "Inactive" and is identified with the last process that used it. This is done to speed up assigning it back to the previous process if it requests it (which of course is quite common).
So as time passes, you'll see less and less Free memory and more and more Inactive memory; this means your Mac is working properly. In fact, after running for a long time, if there's much Free memory left, it is, in a sense, wasted!
The thing to watch for is Paging. If the "Page outs" figure is high, or changing rapidly, then OSX is having to page stuff out because it's out of both Free and Inactive memory.
A better way to monitor page-outs is via a Terminal command. (The Terminal app is in your Applications/Utilities folder.) Enter the following, exactly as shown, at the prompt:
sar -g 60 10
Leave the terminal window open, then try to re-create the unresponsive problem.
This should tell you if you are doing pageouts. You'll see a line in the Terminal window every 60 seconds for 10 minutes (or until you quit Terminal), showing the number of pageouts per second. A few pageouts is normal. If you have large numbers of pageouts, then you have a memory problem.