pg_range
   The catalog pg_range stores information about
   range types.  This is in addition to the types' entries in
   pg_type.
  
Table 52.42. pg_range Columns
| Name | Type | References | Description | 
|---|---|---|---|
| rngtypid | oid |  | OID of the range type | 
| rngsubtype | oid |  | OID of the element type (subtype) of this range type | 
| rngcollation | oid |  | OID of the collation used for range comparisons, or 0 if none | 
| rngsubopc | oid |  | OID of the subtype's operator class used for range comparisons | 
| rngcanonical | regproc |  | OID of the function to convert a range value into canonical form, or 0 if none | 
| rngsubdiff | regproc |  | 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.  rngsubdiff is optional but should be supplied to
   improve performance of GiST indexes on the range type.