ahiguti/HandlerSocket-Plugin-for-MySQL — Issue #70: Handlersocket off by one error in IN() requests
Author: Azhrarn
Created: 2012-01-13 19:35:51+00:00
State: open

(Originally mistakenly posted at https://bugs.launchpad.net/percona-server/+bug/906978 )

Using Percona server 5.5.13-rel20.4-138.lenny with the included Handlersocket plugin and the following config:

handlersocket_verbose = 10
handlersocket_address = '192.168.0.1'
handlersocket_port = 2678
handlersocket_threads = 16 # 2xcpu... 3 x spins wildly out of control
handlersocket_threads_wr = 1
handlersocket_timeout = 30
handlersocket_backlog = 32768
# defaults, 262144 is 256k
handlersocket_sndbuf = 0
handlersocket_rcvbuf = 0
# Set to non 0 if connection pooling/persistent connections are used
handlersocket_accept_balance = 0
handlersocket_wrlock_timeout = 6

There seems to be an odd off by one error when using the IN() syntax (which otherwise seems to work):
"2 > 1 0 5 0 @ 0 4 10 20 30 40"

[Index Id 2 / PRIMARY(id) > 0 / limit 0,5 / id IN(10,20,30,40)]

As an example, the result set here would be user id and user name:

11 / usera, 21 / userb, 31 / userc, 41 / userd

So, it's actually returning the next ID for each in the set (the usernames are correct for the returned 11/21/31/41 ids) rather then the requested IDs. I've been manually fixing this by iterating over my request and decrementing each ID in the IN() section by one.

The second part of this is when using a FILTER argument. The off by one error also seems to show up in the other direction (so I iterate over and increment instead of decrement each element)

If you need any further info or debugging, please let me know. Thanks!