System Function Checking Function

Updated on 2024-12-18 GMT+08:00

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pv_builtin_functions()

Description: Queries information about system functions.

Return type: record

pg_get_functiondef(func_oid)

Description: Gets definition of a function.

Return type: text

func_oid is the OID of the function, which can be queried in the PG_PROC system catalog.

Example: Query the OID and definition of the justify_days function.

    
     
       
       SELECT oid FROM pg_proc WHERE proname ='justify_days';
 oid
------
 1295
(1 row)

SELECT * FROM pg_get_functiondef(1295);
 headerlines |                          definition
-------------+--------------------------------------------------------------
           4 | CREATE OR REPLACE FUNCTION pg_catalog.justify_days(interval)+
             |  RETURNS interval                                           +
             |  LANGUAGE internal                                          +
             |  IMMUTABLE STRICT NOT FENCED NOT SHIPPABLE                  +
             | AS $function$interval_justify_days$function$                +
             |
(1 row)

      

    
   

Note: The query result returned by pg_get_functiondef is in the original text format of the stored procedure. The escape character (\) is used to facilitate subsequent parsing.

pg_get_function_arguments(func_oid)

Description: Gets argument list of function's definition (with default values).

Return type: text

Note: pg_get_function_arguments returns the argument list of a function, in the form it would need to appear in within CREATE FUNCTION.

pg_get_function_identity_arguments(func_oid)

Description: Gets argument list to identify a function (without default values).

Return type: text

Note: pg_get_function_identity_arguments returns the argument list necessary to identify a function, in the form it would need to appear in within ALTER FUNCTION. This form omits default values.