I used to think that performance issue in relational database was always a matter of
:
* missing indexes
* non-used indexes due to query order (where A, B instead of B, A)
But we had the case recently where we optimized a query in postgresql which was taking 100% of cpu during 1s (enough to trigger our alerting) by simply splitting a OR in two separate query.
So if you are looking for optimisation it may be good to know about "OR is bad".
The two queries run in some ms both.
I used to think that performance issue in relational database was always a matter of :
* missing indexes * non-used indexes due to query order (where A, B instead of B, A)
But we had the case recently where we optimized a query in postgresql which was taking 100% of cpu during 1s (enough to trigger our alerting) by simply splitting a OR in two separate query.
So if you are looking for optimisation it may be good to know about "OR is bad". The two queries run in some ms both.