I'm a little bit confused about what EXPLAIN is saying about a query
I'm doing with an ORDER BY clause. I've read and re-read the parts of
the manual about how ORDER BY is optimized, but it won't sink in to my
thick skull for some reason.
I've got an index on a column called price, which is an INT:
mysql> show columns from homes like 'price' \G
*************************** 1. row ***************************
Field: price
Type: int(11)
Null: YES
Key: MUL
Default: NULL
Extra:
1 row in set (0.00 sec)
which I frequently sort by. EXPLAIN says that a filesort is necessary
to do this:
mysql> explain select * from homes order by price \G
*************************** 1. row ***************************
table: homes
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 3628
Extra: Using filesort
1 row in set (0.00 sec)
even when I do an "ALTER TABLE homes ORDER BY price".
Why is a filesort required to sort these rows? Is this something I
should worry about as this system goes from 1500 queries/day to 15000
queries/day to 150000 queries/day? Is there something I can do that
is faster?
Sorry if this is a stupid question; this is the first database I've
designed where I've had to put much thought into performance.
Thanks for any info or pointers to documentation,
-----ScottG.
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