Palle Girgensohn <girgen@pingpong.net> writes:
> Is it always bad to create index xx on yy (field1, field2, field3);
All generalisations are false...
Seriously, it's true that as the length of your index key gets longer the
harder and harder it is to justify it. That doesn't mean they're always wrong,
but you should consider whether a shorter key would perform just as well.
The other problem with long index keys is that they often show up in the same
place as having dozens of indexes on the same table. Usually in shops where
the indexes were created after the fact looking at specific queries.
--
greg