Re: How long is my piece of string?

[Mike Wexler]

Sure. Indices increase the time it takes to add or update a record.
They also take up disk space.
Also when scanning a database, its quicker ot just read the data records directly than to use an index if most of the data records need to be read anyway. For example, if you had a table with 10,000 records and 9,999 records had fielda="a". Then
SELECT * FROM myTable WHERE fieldA="A"
would be quicker without using an index on fieldA than it would be with an index of fieldA.


Mark wrote:

----- Original Message -----
From: "wcb" <[EMAIL PROTECTED]>
To: "MySQL" <[EMAIL PROTECTED]>
Sent: Sunday, December 22, 2002 2:23 AM
Subject: Re: How long is my piece of string?

Hi!

I was interested in the answer to this person's question, too!

The following response:

You need indexes as soon as (or rather just before) they provide
a performance difference.

Alan

seems to lack detail in answering the question, which might be phrased
"when might indices start making a performance difference?".

I would rather reverse the question: is there ever a good reason NOT to use
an index?

- Mark

mysql,query


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