Re: [GENERAL] Multicolumn Index on OR conditions

On 2017-09-19 10:08, Job wrote:
> Hi,
> 
> within a query with two or more conditions with "OR", example:
> 
> "where a = 2 or b < 3"
> 
> could be useful to speed up the query a multi-column index (a,b) even
> though the two conditions are in "OR" and not in "AND"?
> 
> Thank you!
> F

Having any kind of index usually better than none because it may prevent 
a seqscan,
but an OR probably works faster if you have a separate index on B.

But, EXPLAIN can show you what the database actually does, and give some 
indication
of why it thinks it should do it that way.

regards, Vincent.


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