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Showing posts from 2014

update issue in mysql

update table temp set `a`=`a`+1 , `b`= `a`+ 1;

this query sometimes doesn't yield the result we are actually looking for..
so the problem is `a` is getting updated first.

So, the actual query should be :
update table temp set `b`= `a`+ 1, `a`=`a`+1 ;

How to do mass insert in redis

A basic and fairly easy way to do mass insert in redis:

Command to use: echo -e "$(cat redis_mass_insert.txt)" | redis-cli --pipe
Content of file "redis_mass_insert.txt": *3\r\n$5\r\nlpush\r\n$5\r\nu:m:1\r\n$5\r\nvalu1\r\n*3\r\n$5\r\nlpush\r\n$5\r\nu:m:1\r\n$7\r\nmyvalue\r\n

Result: All data transferred. Waiting for the last reply...
ERR unknown command ' *2'
ERR unknown command '$4'
ERR wrong number of arguments for 'echo' command
ERR unknown command '$20'
ERR unknown command ' A�j d�Q;yT��าก �h>'

NOTE: command line will show error but in actual the data is transferred and you can check it by entering in redis.

Here's the snapshot of the whole procedure:

To check how the command is responding: use hexdump -C
Command: echo -n $'$3\r\nset\r\n$3\r\nkey\r\n$5\r\nvalue\r\n ' | hexdump -C
whose output will be something like
00000000 24 33 0d 0a 73 65 74 0d 0a 24 33 0d 0a 6b 65 79 |$3..set..$3..key|
00000010 0d 0a…