Fix Monocle/Alternative out of memory with KEEP_GYM_HISTORY

[j16sdiz]

When KEEP_GYM_HISTORY is on in Monocle/Alternative config, the fort_sighting and raid may contain multiple records of the same gym. Only the latest gym / fort status should be retrieved to avoid out of memory problem.

[CalamityJames]

I would recommend using a PHP function to get time() and pass that through as a parameter as extract(epoch from now()) is not supported on MySQL, and conversely UNIX_TIMESTAMP() is not supported in Postgres

[j16sdiz]

@CalamityJames fixed

[123FLO321]

Working fine for me with KEEP_GYM_HISTORY true

[Glennmen]

This PR should get merged asap, more people are running Monocle Alternative with KEEP_GYM_HISTORY.
The current queries are optimised for Monocle Alternative with KEEP_GYM_HISTORY = false, so we would want to keep those queries for performance improvement.

I was thinking about a config option to switch between KEEP_GYM_HISTORY true/false queries, unless you have a better suggestion.

[j16sdiz]

Actually, the r.time_end >= :time condition save time on both with history and no history case.
It's the condition on fs.last_modified that may harm no history performance.

[Glennmen]

@j16sdiz I think you are right about r.time_end >= :time
Do you think you can add the config option for the other part? (Default for KEEP_GYM_HISTORY = false)

[123FLO321]

last_modified and fort_id are indexed.
I don't think this would impact the ones who don't use KEEP_GYMHISTORY

Can someone with KEEP_GYMHISTORY = False run a performance test on:

SELECT *	
  FROM forts f
  LEFT JOIN fort_sightings fs ON (fs.fort_id = f.id AND fs.last_modified = (SELECT MAX(last_modified) FROM fort_sightings fs2 WHERE fs2.fort_id=f.id))
  WHERE f.id = 1;

vs

SELECT *	
  FROM forts f
  LEFT JOIN fort_sightings fs ON fs.fort_id = f.id
  WHERE f.id = 1;

I did a test with f.id = 1...20 (uncached) on this and got the following result
new avg: 0.071s
old avg: 0.066s

[j16sdiz]

@Glennmen fixed

[j16sdiz]

@123FLO321 There is a 6% to 8% perfomance degrade.
Personally I don't think this worth the extra code for a few milliseconds gain.
But I respect the project owner.

[123FLO321]

I don't like the 1=1 check.
Maybe include the AND inside :fort_condition and replace it with an empty string if $alternateKeepGymHistory is false?