[Vince]

This is used to check that the player who initiated the original query is still connected so the retrieved data doesn't get assigned to another player that just connected with the same playerid. But the chance of that occurring for standard queries* is abysmally small so usually it's not needed and it will only complicate things.

* Certain complex queries which involve large tables and multiple joins can take a few seconds, so in that case it can be useful.

http://en.wikipedia.org/wiki/Race_condition