----- Original Message ----
From: Robert DiFalco <rdifalco@stripped>
To: mysql@stripped
Sent: Thursday, March 9, 2006 9:32:44 AM
Subject: InnoDB Indices
I have some questions regarding InnoDB indices.
Say I have a table with millions of records. On of the fields is a type
field that has a possible value of 1,2,3, or 4. I sometimes query by the
type field and may at other times order on it.
Do queries benefit from an index with this low of a selectivity?
++ For the most part no. I come from Oracle where you can use histograms to help. So,
someone feel free to correct me if I'm wrong.
If through the query browser I find that they do, should I increase the
selectivity of the index by making it a compound index and adding my
Primary Key to the TYPE index?
++ If your primary key will be included in the where clause then definitely include it.
If I make it a compound index, does it have any positive impact on
INSERT, UPDATE, or maybe just DELETE?
++ I can't see it helping with insert, but depending on the where clause on your updates
and deletes it could.
Dave
R.
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