36.24. element_types
  The view
  
   element_types
  
  contains the data type
   descriptors of the elements of arrays.  When a table column, composite-type attribute,
   domain, function parameter, or function return value is defined to
   be of an array type, the respective information schema view only
   contains
  
   ARRAY
  
  in the column
  
   data_type
  
  .  To obtain information on the element
   type of the array, you can join the respective view with this view.
   For example, to show the columns of a table with data types and
   array element types, if applicable, you could do:
 
SELECT c.column_name, c.data_type, e.data_type AS element_type
FROM information_schema.columns c LEFT JOIN information_schema.element_types e
     ON ((c.table_catalog, c.table_schema, c.table_name, 'TABLE', c.dtd_identifier)
       = (e.object_catalog, e.object_schema, e.object_name, e.object_type, e.collection_type_identifier))
WHERE c.table_schema = '...' AND c.table_name = '...'
ORDER BY c.ordinal_position;
 This view only includes objects that the current user has access to, by way of being the owner or having some privilege.
   
    Table 36.22. 
    
     element_types
    
    Columns
   
  
| Name | Data Type | Description | 
|---|---|---|
| 
        object_catalog
        | 
        sql_identifier
        | Name of the database that contains the object that uses the array being described (always the current database) | 
| 
        object_schema
        | 
        sql_identifier
        | Name of the schema that contains the object that uses the array being described | 
| 
        object_name
        | 
        sql_identifier
        | Name of the object that uses the array being described | 
| 
        object_type
        | 
        character_data
        | The type of the object that uses the array being described: one
       of 
        TABLE
       (the array is used by a column of
       that table),
        USER-DEFINED TYPE
       (the array is
       used by an attribute of that composite type),
        DOMAIN
       (the array is used by that domain),
        ROUTINE
       (the array is used by a parameter or
       the return data type of that function). | 
| 
        collection_type_identifier
        | 
        sql_identifier
        | The identifier of the data type descriptor of the array being
       described.  Use this to join with the 
        dtd_identifier
       columns of other information
       schema views. | 
| 
        data_type
        | 
        character_data
        | Data type of the array elements, if it is a built-in type, else 
        USER-DEFINED
       (in that case, the type is
       identified in
        udt_name
       and associated
       columns). | 
| 
        character_maximum_length
        | 
        cardinal_number
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        character_octet_length
        | 
        cardinal_number
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        character_set_catalog
        | 
        sql_identifier
        | Applies to a feature not available in PostgreSQL | 
| 
        character_set_schema
        | 
        sql_identifier
        | Applies to a feature not available in PostgreSQL | 
| 
        character_set_name
        | 
        sql_identifier
        | Applies to a feature not available in PostgreSQL | 
| 
        collation_catalog
        | 
        sql_identifier
        | Name of the database containing the collation of the element type (always the current database), null if default or the data type of the element is not collatable | 
| 
        collation_schema
        | 
        sql_identifier
        | Name of the schema containing the collation of the element type, null if default or the data type of the element is not collatable | 
| 
        collation_name
        | 
        sql_identifier
        | Name of the collation of the element type, null if default or the data type of the element is not collatable | 
| 
        numeric_precision
        | 
        cardinal_number
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        numeric_precision_radix
        | 
        cardinal_number
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        numeric_scale
        | 
        cardinal_number
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        datetime_precision
        | 
        cardinal_number
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        interval_type
        | 
        character_data
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        interval_precision
        | 
        cardinal_number
        | Always null, since this information is not applied to array element data types in PostgreSQL | 
| 
        domain_default
        | 
        character_data
        | Not yet implemented | 
| 
        udt_catalog
        | 
        sql_identifier
        | Name of the database that the data type of the elements is defined in (always the current database) | 
| 
        udt_schema
        | 
        sql_identifier
        | Name of the schema that the data type of the elements is defined in | 
| 
        udt_name
        | 
        sql_identifier
        | Name of the data type of the elements | 
| 
        scope_catalog
        | 
        sql_identifier
        | Applies to a feature not available in PostgreSQL | 
| 
        scope_schema
        | 
        sql_identifier
        | Applies to a feature not available in PostgreSQL | 
| 
        scope_name
        | 
        sql_identifier
        | Applies to a feature not available in PostgreSQL | 
| 
        maximum_cardinality
        | 
        cardinal_number
        | Always null, because arrays always have unlimited maximum cardinality in PostgreSQL | 
| 
        dtd_identifier
        | 
        sql_identifier
        | An identifier of the data type descriptor of the element. This is currently not useful. |