1282311 - deleting history V.....E.....R.....Y..... S..........L..........O..........W.......... (very slow)

Status: RESOLVED DUPLICATE of bug 734643

(Firefox :: Untriaged, defect)

Description

[u123541]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:50.0) Gecko/20100101 Firefox/50.0
Build ID: 20160616163918

Steps to reproduce:

Tried to delete history older than 6 months (80,200+) -- IIRC, about 80,253


Actual results:

100% CPU.
Close button ignored.
Killed process after 3+ HOURS.
Restarted Nightly.
Still have 77,953 items.

Now trying to delete in chunks...  ~20 at a time is very quick.
5000 at a time seems to be done in chunks of 300 at a time.
Deleted 6300 in 1:25 minute -- so 80K should take about 18 minutes.

Apparently, there must be a number, above which performance takes a SERIOUS hit...

Trying 20,000 -- not moving by 300...  killed since this is too slow.
         10,000 -- about 20 seconds per 300; but MUCH faster at the end. (4:56)
           5,000 -- (0:48)
Grand total is now down to 48640.  Will now delete 5000 at a time to see if the total size matters...
           5,000 -- (0:46)
           5,000 -- (0:46)
           5,000 -- (0:42)
           5,000 -- (0:42)
28,640 remaining...
           3,000 -- (0:19) -- definitely non-linear 
           3,000 -- (0:17) 
           3,000 -- (0:17) 
           3,000 -- (0:17) 
           3,000 -- (0:15) 
           3,000 -- (0:15) 
           6,000 -- (1:01)
             rest -- (0:31)

The last sets of deletions seemed to  occur in steps of 600...  Clearly the time to delete grows dramatically as the number of deletions selected grows; not so much affected by the total entries.  If this too becomes a WONTFIX; I'd suggest at least [suggesting] limiting the deletions to some number that is a multiple of 300|600 and where the time grows very fast...  3000 seems reasonable.

Heck, wouldn't repeatedly calling the bulk delete in chunks of say 3000 be much faster than choking it with the initial 80K+?

Based on the initial delete attempt, ~3500 deletions took over 3 hours v. ~20-30 seconds it would have taken if only those had been selected.