37.24. 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 37.22. element_types Columns
Column Type Description |
|---|
Name of the database that contains the object that uses the array being described (always the current database) |
Name of the schema that contains the object that uses the array being described |
Name of the object that uses the array being described |
The type of the object that uses the array being described: one of |
The identifier of the data type descriptor of the array being described. Use this to join with the |
Data type of the array elements, if it is a built-in type, else |
Always null, since this information is not applied to array element data types in PostgreSQL |
Always null, since this information is not applied to array element data types in PostgreSQL |
Applies to a feature not available in PostgreSQL |
Applies to a feature not available in PostgreSQL |
Applies to a feature not available in PostgreSQL |
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 |
Name of the schema containing the collation of the element type, null if default or the data type of the element is not collatable |
Name of the collation of the element type, null if default or the data type of the element is not collatable |
Always null, since this information is not applied to array element data types in PostgreSQL |
Always null, since this information is not applied to array element data types in PostgreSQL |
Always null, since this information is not applied to array element data types in PostgreSQL |
Always null, since this information is not applied to array element data types in PostgreSQL |
Always null, since this information is not applied to array element data types in PostgreSQL |
Always null, since this information is not applied to array element data types in PostgreSQL |
Not yet implemented |
Name of the database that the data type of the elements is defined in (always the current database) |
Name of the schema that the data type of the elements is defined in |
Name of the data type of the elements |
Applies to a feature not available in PostgreSQL |
Applies to a feature not available in PostgreSQL |
Applies to a feature not available in PostgreSQL |
Always null, because arrays always have unlimited maximum cardinality in PostgreSQL |
An identifier of the data type descriptor of the element. This is currently not useful. |