Re: Poor performance when using a large Limit offset

[Craig Matthews]

Hi James/Xuefer,

I have a huge table (1 million rows now) which is working quite alright with about five composite indexes on selected rows.

It's mostly a SELECT table though so I'm thinking of a "covering index". Where can I read about the pros and cons of this type of index? Couldnt find it in the manual:

http://dev.mysql.com/doc/mysql/search.php?q=covering+index&from=%2Fdoc%2Fmysql%2Fen%2Findex.html&lang=en

MY QUESTION:

Would having a covering index *apart from the existing composite indexes* be a problem, because several of the columns would of course be repeated? This may also make the size of the index larger than the actual data set in our case, is that unacceptable in any way?

Thanks for any thoughts!