MySQL Forums
Forum List  »  Newbie

Innodb PK in secondary index
Posted by: Robert Waters
Date: June 10, 2010 07:02PM

MySQL@Facebook recently posted an article on speeding up queries with LIMIT clauses ("LIMIT a, b is O(N*N)":

The user indicates that creating a compound index (containing both the indexed field and the pk field) and then using a specially-formed query will speed up certain queries:
"Indexing all columns from the PRIMARY index is not as horrible as you might think when using InnoDB because all secondary index entries contain the PRIMARY key columns as the row pointer."

I thought that all InnoDB secondary indexes contained the PK (per, and so I am not really sure what this user is trying to say.

Also, I do not really understand the select query at the end of the article (what are "$last_j" and "$last_i", are they the same as "$offset"?).

I'd reply to the post, but it is a few months old and I am not sure I'd get an answer.


Options: ReplyQuote

Written By
Innodb PK in secondary index
June 10, 2010 07:02PM

Sorry, you can't reply to this topic. It has been closed.

Content reproduced on this site is the property of the respective copyright holders. It is not reviewed in advance by Oracle and does not necessarily represent the opinion of Oracle or any other party.