在MySQL查询中使用OR时，有没有办法使用索引来避免文件排序？

Question

I have the following query and the following 2 indexes, but I am still getting a filesort. Is there a way to optimize this further so that I avoid the filesort, or do I just need to live with it?

Query:

SELECT * FROM table WHERE row1 > '0' OR row2 = '1' ORDER BY id DESC

Indexes:

row1

row2,id

EXPLAIN output:

Using sort_union(row1,row2_id); Using where; Using filesort

Answer 1

ORDER BY ROW2，ID或在ID上添加索引。

Answer 2

Yes, you can. Just add index like (id, row1, row2).

This index will work, because rows in it will be pre-sorted and mySQL will only need to select the satisfying lines.

Moreover, sort_union() index merging is not THAT good optimization for mySQL anyway.

Answer 3

It's a little bit late for answering but i want to say that, using "or" probably causing that problem. You can try using union with two different queries.