Contains information about fields returned by the server
If the field can be identified as a column of a specific table, the attribute number of the column; otherwise zero.
The type modifier (see pg_attribute.atttypmod). The meaning of the modifier is type-specific.
The field name.
The object ID of the field's data type.
If the field can be identified as a column of a specific table, the object ID of the table; otherwise zero.
The data type size (see pg_type.typlen). Note that negative values denote variable-width types.