database - mysql suddenly ignoring table indices for a time -


on our mysql 5.1 server innodb table called central our web application. has around 150,000 rows , far many columns due bad implementation.

lately we've been running task updates table (insert or update) once every few seconds.

when task running, database periodically (every 1 - 3 hours) become slower process client read requests. during times slow_log points table culprit , request looks it's doing full table scan. eventually, within 5-20 minutes work out , go processing normally.

my assumption constant table updates throwing mysql's query optimizer statistics out of whack every once in while. don't know how prove or find solution it.

can following causes?

  1. too many secondary indices on table (there ~45, many unnecessary take time , care prune away)
  2. bad configuration parameters (query_cache on , innodb_buffer @ 5g)
  3. mysql 5.1 outdated , should upgraded
  4. the database server needs more ram/cpu handle load

i more happy provide additional information might request in comments.

can following causes?

too many secondary indices on table (there ~45, many unnecessary take time , care prune away)

yes, if running task witch lot of inserts/updates sure having lots of indexes in table overload sql engine. take in account every insert/update, sql has same insert each index. try keep indexes needed. , if amount of selects bigger insert statements.

bad configuration parameters (query_cache on , innodb_buffer @ 5g)

true, query_cache can or not, depends on ram amount dedicated (query_cache_size) , total ram amount server have. best assign small amount, check performance, increase amount, again check if goes better , on. other options key_buffer (important! if have many indexes) can decisive.

mysql 5.1 outdated , should upgraded

well, of course it's important upgrade , boosts performance wouldn't expect resolve problem.

the database server needs more ram/cpu handle load

we same here, priorize on db design , optimizing queries.


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