element_typesThe 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
|
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. |
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