transforms contains information about the transforms defined in the current database. More precisely, it contains a row for each function contained in a transform (the “from SQL” or “to SQL” function).
Name of the database that contains the type the transform is for (always the current database)
Name of the schema that contains the type the transform is for
Name of the type the transform is for
Name of the database containing the function (always the current database)
Name of the schema containing the function
The “specific name” of the function. See Section 36.41 for more information.
The SQL standard allows defining transforms in “groups”, and selecting a group at run time. PostgreSQL does not support this. Instead, transforms are specific to a language. As a compromise, this field contains the language the transform is for.