PG_RANGE records information about range types.

This is in addition to the types' entries in PG_TYPE.

**Table 1** PG_RANGE columns
Name	Type	Reference	Description
rngtypid	oid	PG_TYPE.oid	OID of the range type
rngsubtype	oid	PG_TYPE.oid	OID of the element type (subtype) of this range type
rngcollation	oid	PG_COLLATION.oid	OID of the collation used for range comparisons, or 0 if none
rngsubopc	oid	PG_OPCLASS.oid	OID of the subtype's operator class used for range comparisons
rngcanonical	regproc	PG_PROC.oid	OID of the function to convert a range value into canonical form, or 0 if none
rngsubdiff	regproc	PG_PROC.oid	OID of the function to return the difference between two element values as double precision, or 0 if none

rngsubopc (plus rngcollation, if the element type is collatable) determines the sort ordering used by the range type. rngcanonical is used when the element type is discrete.