sql查询计数两个“未知”列的总和

Question

I need to query for the COUNT of rows that fulfill multiple filter criteria. However, I do not know which filters will be combined, so I cannot create appropriate indexes.

SELECT COUNT(id) FROM tbl WHERE filterA > 1000 AND filterD < 500

This is very slow since it has to do a full table scan. Is there any way to have a perfomant query in my situation?

 id, filterA, filterB, filterC, filterD, filterE
    1, 2394, 23240, 8543, 3241, 234, 23

Answer 1

The issue here is that there are certain limitations in how you can index data on multiple criteria. These are standard, fundamental issues and to the extent that ElasticSearch is able to get away from the problems it is just brute force parallelism and indexes on everything you may want to filter by.

Usually some filters will be more commonly used and more selective, so usually one would start by looking at actual examples of queries and build indexes around the queries which have performed slowly in the past.

This means you start with slow query logging and then focus on the most important queries first until you get everything where it is tolerable.