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.
