A SQL query searching for rows that satisfy Column1 <= X <= Column2 is very slow

Question

I am using a MySQL DB, and have the following table:

CREATE TABLE SomeTable (
  PrimaryKeyCol BIGINT(20) NOT NULL,
  A BIGINT(20) NOT NULL,
  FirstX INT(11) N         


        

Answer 1

To optimize this query:

SELECT P, Y, Z FROM SomeTable WHERE FirstX <= ? AND LastX >= ? LIMIT 10;

Here's 2 resources you can use:

• descending indexes
• spatial indexes

Descending indexes:

One option is to use an index that is descending on FirstX and ascending on LastX.

https://dev.mysql.com/doc/refman/8.0/en/descending-indexes.html

something like:

CREATE INDEX SomeIndex on SomeTable (FirstX DESC, LastX);

Conversely, you could create instead the index (LastX, FirstX DESC).

Spatial indexes:

Another option is to use a SPATIAL INDEX with (FirstX, LastX). If you think of FirstX and LastX as 2D spatial coordinates, then your search what it does is select the points in a contiguous geographic area delimited by the lines FirstX<=LastX, FirstX>=0, LastX>=X.

Here's a link on spatial indexes (not specific to MySQL, but with drawings):

https://docs.microsoft.com/en-us/sql/relational-databases/spatial/spatial-indexes-overview