| PostgreSQL 9.2.4 Documentation | ||||
|---|---|---|---|---|
| Prev | Up | Chapter 34. The Information Schema | Next | |
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 34-21. 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. |
Please use this form to add your own comments regarding your experience with particular features of PostgreSQL, clarifications of the documentation, or hints for other users. Please note, this is not a support forum, and your IP address will be logged. If you have a question or need help, please see the faq, try a mailing list, or join us on IRC. Note that submissions containing URLs or other keywords commonly found in 'spam' comments may be silently discarded. Please contact the webmaster if you think this is happening to you in error.
Proceed to the comment form.