Arun Kumar PG wrote:
Guys,
I know this is a stupid thing but I wanted to know if we have an index
on a
column "X" and if i have a query having 10000 OR conditions on the
field e.g.
where X=10 OR x=12 OR x=13 OR x=15...... so on then will it give any
benefits in terms of speed?
Yes the index still works. I construct queries that have a decent number
of OR conditions ( I default mine to limit to 100 conditions, all on the
primary key ), and I get very good performance ( not only from MySQL, by
the way, this seems to work on a number of different DB servers ). Keep
in mind the max_packet_size for MySQL ( I think this is the one to watch
anyway ). If your query exceeds this size, you're in trouble.
Just for interest, I tried pushing my default to 10,000, then 20,000,
and I still get amazingly good performance. Cool :) The reason I default
to 100 is so I get decent performance across slow network connections (
eg DSL ).
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