MySQL Bugs: #70775: Docs advice on query cache might be misleading

Bug #70775	Docs advice on query cache might be misleading
Submitted:	30 Oct 2013 19:11	Modified:	29 Sep 2017 23:00
Reporter:	Morgan Tocker	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:		OS:	Any
Assigned to:	Paul DuBois	CPU Architecture:	Any

Description:
On the page: http://dev.mysql.com/doc/refman/5.6/en/optimizing-innodb-queries.html it mentions:
"If you often have recurring queries for tables that are not updated frequently, enable the query cache:"

I think that we should include some sort of warning, since the query cache is known to have negative performance even in this situation.  If the queries are recurring but well indexed, it is also less likely there will be a large improvement.

How to repeat:
Following these steps might get a user in trouble.

Suggested fix:
I suggest either removing this point, or changing the wording to include a caveat.

Hello Morgan,

Thank you for the valuable feedback.

Thanks,
Umesh

A few other pages that could potentially be updated:

* http://dev.mysql.com/doc/refman/5.6/en/upgrading-from-previous-series.html -> Some users with unoptimized queries may be caught with suddenly slower queries.  Here is an example: http://dba.stackexchange.com/questions/66774/why-query-cache-type-is-disabled-by-default-s...

* http://dev.mysql.com/doc/refman/5.6/en/query-cache.html -> Needs a warning.

Posted by developer:
 
Removed the text in question. Seems the best course of action,
particularly since the query cache is now deprecated in MySQL 5.7
and removed in 8.0.