luhuayi
177cd61a57
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com> Co-authored-by: luhuayi <luhuayi@huawei.com> Co-committed-by: luhuayi <luhuayi@huawei.com>
6.9 KiB
Comment Checking Functions
col_description(table_oid, column_number)
Description: Gets comment for a table column.
Return type: text
Note: col_description returns the comment for a table column, which is specified by the OID of its table and its column number.
Example: Query the pg_class system catalog to obtain the table OID, and query the INFORMATION_SCHEMA.COLUMNS system view to obtain column_number.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | SELECT COLUMN_NAME,ORDINAL_POSITION FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 't' AND COLUMN_NAME = 'a'; column_name | ordinal_position -------------+------------------ a | 1 (1 row) SELECT oid FROM pg_class WHERE relname='t'; oid ------- 44020 (1 row) SELECT col_description(44020,1); col_description ----------------------- This is a test table. (1 row) |
obj_description(object_oid, catalog_name)
Description: Gets comment for a database object.
Return type: text
Note: The two-parameter form of obj_description returns the comment for a database object specified by its OID and the name of the containing system catalog. For example, obj_description(123456,'pg_class') would retrieve the comment for the table with OID 123456. The one-parameter form of obj_description requires only the object OID.
obj_description cannot be used for table columns since columns do not have OIDs of their own.
obj_description(object_oid)
Description: Gets comment for a database object.
Return type: text
shobj_description(object_oid, catalog_name)
Description: Gets comment for a shared database object.
Return type: text
Note: The functions of shobj_description and obj_description are similar. The only difference is that shobj_description is used for shared objects. Some system catalogs are global to all databases within each cluster, and the comments for objects in them are stored globally as well.