.mysql_history not being saved automatically - mysql

Question

I've been unable to get mysql command-line history working for my user, even though it works fine for other users on the same machine (mysql 5.5 on Debian "wheezy" distro.) I'm at wit's end, and am hoping someone here can help me...
Whenever I start mysql, I have no history to scroll back to (it just gives a visual bell alert when I try up-arrow for example).
However, as I'm using it, history works fine (within a single session). I.e., I can go back to earlier commands since I started mysql. But, the second I quit mysql, I lose all my history and have to start over again the next time.
Needless to say, this is extremely frustrating!
To troubleshoot, I did three things, none of which made any difference at all:
(1) I explicitly set the environment variable (using bash):
% MYSQL_HISTFILE=~/.mysql_history
% echo $MYSQL_HISTFILE
/var/home/userx/.mysql_history
... and I double-checked that the permissions were set correctly (both on the file and on the directory -- note, I created an empty file just to be sure it wasn't having trouble creating it itself):
drwxr-xr-x 53 userx userx 4096 Jan 24 15:26 /var/home/userx
-rw------- 1 userx userx 0 Jan 31 04:14 /var/home/userx/.mysql_history
I confirm it is "-rw-------" and the file is owned by the user in question (me), identically to all the other users on the same machine for whom it works fine. Though, the mysql client documentation doesn't say you need to set this environment variable unless you want to change it (so I've of course tried it without setting that variable as well).
(2) I tried setting/tweaking various logging-related configs in /etc/mysql/my.cnf (from looking at the documentation; however, all of the settings seem to truly be about logging, not about command-line history).
None of the settings in /etc/mysql/*.cnf seems to have anything to do with the command-line logging (only with server-level logging, e.g. to /var/log/mysql...).
To be sure, I reverted everything back to how it was in the standard installation (via debian wheezy apt-get install mysql) so any of my mucking around couldn't actually have been the reason. (Note: it works fine for other users on the same exact machine!)
(3) I tried examining/tweaking various variables within mysql itself (based on various things I've seen posted). But these are hard to find good information on, and since it works for other users on the same machine, I'm skeptical whether this will matter. Anyway, here's what I did here:
First, to get a list of all currently-set variables, I did:
% echo "show variables" | mysql > /tmp/vars
Looking through them, I didn't see anything that seemed to be relevant. But here're some examples (it's too long to dump all of them here; let me know if there's one variable or one search I can do that may yield the answer, though):
% grep -i hist /tmp/vars
performance_schema_events_waits_history_long_size 10000
performance_schema_events_waits_history_size 10
profiling_history_size 15
... as well as ...
% grep -i log /tmp/vars (note: irrelevant binlog stuff excerpted)
back_log 50
expire_logs_days 10
general_log OFF
general_log_file /var/lib/mysql/xxx.log
innodb_log_group_home_dir ./
innodb_mirrored_log_groups 1
log OFF
log_error
log_output FILE
log_queries_not_using_indexes OFF
log_slave_updates OFF
log_slow_queries OFF
log_warnings 1
slow_query_log OFF
slow_query_log_file /var/lib/mysql/rimu3-slow.log
None of these seems relevant, nor did anything I did based on various web search relating to changing variables solve my problem -- and, remember: none of the other users on the same machine has this problem. So unless the variables or other server state I haven't found actually specifically refers to my user, or there is some access policy somewhere I haven't discovered that specifically refers to my user (for example), this is just not explainable.
The only documentation I can find anywhere about the mysql_history file is here. But it doesn't tell you how to enable mysql_history! (It only says how to disable it, or to change where it goes, which also doesn't change anything for me.)
To wrap up, I have confirmed that, in the end, my troubleshooting didn't end up leaving anything set incorrectly: I'm back to the standard environment variables, server configs, variables, etc.
I'm really completely stumped here. Any help would be immensely appreciated!
Steve

Answer 1

I found the problem.
There are actually two files used for mysql history: ~/.mysql_history and ~/.mysql_history.TMP. I only discovered the second file using ptrace:
open("/var/home/userx/.mysql_history.TMP", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0600) = -1 EACCES (Permission denied)
Knowing that there are two files, the issue becomes much clearer:
% ls ~/.mysql_history*
-rw------- 1 userx userx 0 Jan 31 04:14 /var/home/userx/.mysql_history
-rw------- 1 root root 279506 May 11 2014 /var/home/userx/.mysql_history.TMP
(And yes, this problem has gone back to May 2014, so that makes it all make so much sense now.)
In my case, I had root access via sudo, so I could easily fix it:
% sudo chown userx:userx /home/userx/.mysql_history.TMP
And the subsequent use of mysql worked perfectly (though all my history in between was still lost forever). :-(
The root problems are:
(a) mysql documentation makes no mention of this file (and in fact, shouldn't really need it), and
(b) mysql client doesn't give any error message to the end user letting them know this file is unmodifiable either at start-up or at exit.
--
So, there you have it, in a nutshell:
(1) The mysql documentation fails to mention anywhere that it uses .mysql_history.TMP that needs the same permissions.
(2) Using a wrapper like rlwrap worked around this (see my comment above) because it apparently doesn't use that .TMP version of the file.
Steve