Re: RFC: replace pg_stat_activity.waiting with something more descriptive

Hello.

I did some refactoring to previous patch. Improvements:

1) Wait is determined by class and event without affecting to atomic usage of it. 

They are still stored in one variable. This improvement gives an opportunity to make  

more detailed views later (waits can be grouped by class).

2) Only active wait of each backend is visible. pg_report_wait_end() function called
on the end of wait and clears it.
3) Wait name determination was optimized (last version used cycles for each of them, 

and was very heavy). I added lazy `group` field to LWLock, which used as index in
lwlock names array.

4) New wait can be added by more simpler way. For example an individual lwlock

requires only specifying its name in LWLock names arrayb

5) Added new types of waits: Storage, Network, Latch

This patch is more informative and it'll be easier to extend.

Sample:

b1=# select pid, wait_event from pg_stat_activity;

pid  |          wait_event          

-------+------------------------------

17099 | LWLocks: BufferCleanupLock

17100 | Locks: Transaction

17101 | LWLocks: BufferPartitionLock

17102 | 

17103 | Network: READ

17086 | 

(6 rows)

-- 
Ildus Kurbangaliev
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company