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Re: Find free appointments faster
Posted by: Øystein Grøvlen
Date: November 14, 2017 09:31AM

Hi,

It may be that the condition on date reduces the number of candidate rows so much that the additional savings from using the index to restrict on time_start/time_end is smaller than the overhead of more subqueries. So it might not be more to save here.

If you need to add/substract a second, you should do it to the operand that is constant not to the column since the latter prevents the use of index. However, I think you can achieve what you want without adding seconds. If you have to intervals (a,b) and (c,d), could you not say that these overlap only if
c < b <= d OR a < d <= b
I.e., intervals do not overlap when start time of one interval equals end time of the other.

Øystein Grøvlen,
Senior Principal Software Engineer,
MySQL Group, Oracle,
Trondheim, Norway

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