Re: Multiple-Table-Spanning Joins with ORs in WHERE Clause - Mailing list pgsql-performance

Well, I don't recall seeing this issue on this list before (or a few other forums I read) while I see several other issues over and over again.  So that is why I think it is a niche issue.  Perhaps I've have seen it before and just forgotten, or have not recognized it as being the same issue each time.

Understood.

 

This multitude of solution also shows that applications developers might be overwhelmed by choosing the most appropriate AND most long-lasting one. Because what I take from the discussion is that a UNION might be appropriate right now but that could change in the future even for the very same use-case at hand.

I'm not sure what would cause it to change.  Do you mean if you suddenly start selecting a much larger portion of the table?  I don't know that the union would be particularly bad in that case, either.

Not suddenly but gradually. Data can change and we don't know for sure how people will use our systems in the future. Hence, another plan would be more optimal or even a seq scan on big_table would be faster.

In the case at hand, I doubt it but you never know.

I'm not saying it wouldn't be nice to fix it.  I just don't think it is particularly likely to happen soon.  I could be wrong (especially if you can write the code to make it happen).

I have been thinking about this. It would be an interesting exercise as I haven't written much of C in the last decade but sometimes one needs to get out of the comfort zone to get things going.


Sven