Specify an operator class

An operator class identifies the functions that a secondary access method needs to build, scan, and maintain the entries in an index.

You can associate an access method with multiple operator classes, particularly if the indexes that use the access method involve multiple data types. For example, the following indexes might require multiple operator classes:

CREATE TABLE sheet_music (col1 beat, col2 timbre, col3 chord)
CREATE INDEX tone ON music(timbre, chord) USING music_am
CREATE INDEX rhythm ON music(beat) USING music_am

Use a different function to compare values of data type chord from that which you use to compare values of data type timbre.