18th October 2018: PostgreSQL 11 Released!
Supported Versions: Current (11) / 10 / 9.6 / 9.5 / 9.4 / 9.3
Development Versions: devel
Unsupported versions: 9.2 / 9.1 / 9.0 / 8.4 / 8.3 / 8.2 / 8.1 / 8.0 / 7.4 / 7.3

3.8. pg_cast

pg_cast stores data type conversion paths, both built-in paths and those defined with CREATE CAST.

Table 3-8. pg_cast Columns

Name Type References Description
castsource oid pg_type.oid OID of the source data type
casttarget oid pg_type.oid OID of the target data type
castfunc oid pg_proc.oid The OID of the function to use to perform this cast. Zero is stored if the data types are binary coercible (that is, no run-time operation is needed to perform the cast).
castcontext char   Indicates what contexts the cast may be invoked in. e means only as an explicit cast (using CAST, ::, or function-call syntax). a means implicitly in assignment to a target column, as well as explicitly. i means implicitly in expressions, as well as the other cases.