Hi Douglas,

> But when I try a near-neighbor count in that small section I get:
>
> mysql> SELECT COUNT(*) FROM Object o1, Object o2
>       -> WHERE qserv_areaspec_box(1,2,3,4)
>       -> AND qserv_angSep(o1.ra_PS, o1.decl_PS,o2.ra_PS, o2.decl_PS) < 0.1;
> ERROR 4120 (Proxy): Error during execution: 'read failed for chunk(s):
> 14880 14641 14640 14881'
>
> So, not sure what is happening there?
May I ask that whenever you get "read failed", you check the worker log 
to see what the actual error was?

It is a weakness in the worker protocol that the result must be a dump 
file. Unfortunately, we don't provide a header (which could indicate a 
rich error) or other bundling of the dump. So... "read failed" means the 
worker couldn't execute the query (though it tried).
This could be:
* syntax error (and over-long column expressions in select)
* mysql read permissions error
* mysql write permissions error
* dump file write error
* dump file read error
* worker memory corruption

We can work on the result error handling, but that's not going to get 
done in a short time scale. Could probably hack something together in a 
couple days, that would then undergo the same shakedown process as any 
other feature, and that's probably too slow for you.

I'll add the note to the troubleshooting page.

-Daniel

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