DROP FUNCTION without knowing the number/type of parameters? - sql

Question

I keep all my functions in a text file with 'CREATE OR REPLACE FUNCTION somefunction'.
So if I add or change some function I just feed the file to psql.
Now if I add or remove parameters to an existing function, it creates an overload with the same name and to delete the original I need type in all the parameter types in the exact order which is kind of tedious.
Is there some kind of wildcard I can use to DROP all functions with a given name so I can just add DROP FUNCTION lines to the top of my file?

Answer 1

Basic query
This query creates all necessary DDL statements:
SELECT 'DROP FUNCTION ' || oid::regprocedure
FROM pg_proc
WHERE proname = 'my_function_name' -- name without schema-qualification
AND pg_function_is_visible(oid); -- restrict to current search_path
Output:
DROP FUNCTION my_function_name(string text, form text, maxlen integer);
DROP FUNCTION my_function_name(string text, form text);
DROP FUNCTION my_function_name(string text);
Execute the commands after checking plausibility.
Pass the function name case-sensitive and with no added double-quotes to match against pg_proc.proname.
The cast to the object identifier type regprocedure (oid::regprocedure), and then to text implicitly, produces function names with argument types, automatically double-quoted and schema-qualified according to the current search_path where needed. No SQL injection possible.
pg_function_is_visible(oid) restricts the selection to functions in the current search_path ("visible"). You may or may not want this.
If you have multiple functions of the same name in multiple schemas, or overloaded functions with various function arguments, all of those will be listed separately. You may want to restrict to specific schema(s) or specific function parameter(s).
Related:
When / how are default value expression functions bound with regard to search_path?
Function
You can build a plpgsql function around this to execute the statements immediately with EXECUTE. For Postgres 9.1 or later:
Careful! It drops your functions!
CREATE OR REPLACE FUNCTION f_delfunc(_name text, OUT functions_dropped int)
LANGUAGE plpgsql AS
$func$
-- drop all functions with given _name in the current search_path, regardless of function parameters
DECLARE
_sql text;
BEGIN
SELECT count(*)::int
, 'DROP FUNCTION ' || string_agg(oid::regprocedure::text, '; DROP FUNCTION ')
FROM pg_catalog.pg_proc
WHERE proname = _name
AND pg_function_is_visible(oid) -- restrict to current search_path
INTO functions_dropped, _sql; -- count only returned if subsequent DROPs succeed
IF functions_dropped > 0 THEN -- only if function(s) found
EXECUTE _sql;
END IF;
END
$func$;
Call:
SELECT f_delfunc('my_function_name');
The function returns the number of functions found and dropped if no exceptions are raised. 0 if none were found.
Further reading:
How does the search_path influence identifier resolution and the "current schema"
Truncating all tables in a Postgres database
PostgreSQL parameterized Order By / Limit in table function
For Postgres versions older than 9.1 or older variants of the function using regproc and pg_get_function_identity_arguments(oid) check the edit history of this answer.

Answer 2

You would need to write a function that took the function name, and looked up each overload with its parameter types from information_schema, then built and executed a DROP for each one.
EDIT: This turned out to be a lot harder than I thought. It looks like information_schema doesn't keep the necessary parameter information in its routines catalog. So you need to use PostgreSQL's supplementary tables pg_proc and pg_type:
CREATE OR REPLACE FUNCTION udf_dropfunction(functionname text)
RETURNS text AS
$BODY$
DECLARE
funcrow RECORD;
numfunctions smallint := 0;
numparameters int;
i int;
paramtext text;
BEGIN
FOR funcrow IN SELECT proargtypes FROM pg_proc WHERE proname = functionname LOOP
--for some reason array_upper is off by one for the oidvector type, hence the +1
numparameters = array_upper(funcrow.proargtypes, 1) + 1;
i = 0;
paramtext = '';
LOOP
IF i < numparameters THEN
IF i > 0 THEN
paramtext = paramtext || ', ';
END IF;
paramtext = paramtext || (SELECT typname FROM pg_type WHERE oid = funcrow.proargtypes[i]);
i = i + 1;
ELSE
EXIT;
END IF;
END LOOP;
EXECUTE 'DROP FUNCTION ' || functionname || '(' || paramtext || ');';
numfunctions = numfunctions + 1;
END LOOP;
RETURN 'Dropped ' || numfunctions || ' functions';
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
I successfully tested this on an overloaded function. It was thrown together pretty fast, but works fine as a utility function. I would recommend testing more before using it in practice, in case I overlooked something.

Answer 3

Improving original answer in order to take schema into account, ie. schema.my_function_name,
select
format('DROP FUNCTION %s(%s);',
p.oid::regproc, pg_get_function_identity_arguments(p.oid))
FROM pg_catalog.pg_proc p
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = p.pronamespace
WHERE
p.oid::regproc::text = 'schema.my_function_name';

Answer 4

Slightly enhanced version of Erwin's answer. Additionally supports following
'like' instead of exact function name match
can run in 'dry-mode' and 'trace' the SQL for removing of the functions
Code for copy/paste:
/**
* Removes all functions matching given function name mask
*
* #param p_name_mask Mask in SQL 'like' syntax
* #param p_opts Combination of comma|space separated options:
* trace - output SQL to be executed as 'NOTICE'
* dryrun - do not execute generated SQL
* #returns Generated SQL 'drop functions' string
*/
CREATE OR REPLACE FUNCTION mypg_drop_functions(IN p_name_mask text,
IN p_opts text = '')
RETURNS text LANGUAGE plpgsql AS $$
DECLARE
v_trace boolean;
v_dryrun boolean;
v_opts text[];
v_sql text;
BEGIN
if p_opts is null then
v_trace = false;
v_dryrun = false;
else
v_opts = regexp_split_to_array(p_opts, E'(\\s*,\\s*)|(\\s+)');
v_trace = ('trace' = any(v_opts));
v_dryrun = ('dry' = any(v_opts)) or ('dryrun' = any(v_opts));
end if;
select string_agg(format('DROP FUNCTION %s(%s);',
oid::regproc, pg_get_function_identity_arguments(oid)), E'\n')
from pg_proc
where proname like p_name_mask
into v_sql;
if v_sql is not null then
if v_trace then
raise notice E'\n%', v_sql;
end if;
if not v_dryrun then
execute v_sql;
end if;
end if;
return v_sql;
END $$;
select mypg_drop_functions('fn_dosomething_%', 'trace dryrun');

Answer 5

Here is the query I built on top of #Сухой27 solution that generates sql statements for dropping all the stored functions in a schema:
WITH f AS (SELECT specific_schema || '.' || ROUTINE_NAME AS func_name
FROM information_schema.routines
WHERE routine_type='FUNCTION' AND specific_schema='a3i')
SELECT
format('DROP FUNCTION %s(%s);',
p.oid::regproc, pg_get_function_identity_arguments(p.oid))
FROM pg_catalog.pg_proc p
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = p.pronamespace
WHERE
p.oid::regproc::text IN (SELECT func_name FROM f);

Answer 6

As of Postgres 10 you can drop functions by name only, as long as the names are unique to their schema. Just place the following declaration at the top of your function file:
drop function if exists my_func;
Documentation here.

Answer 7

pgsql generates an error if there exists more than one procedure with the same name but different arguments when the procedure is deleted according to its name. Thus if you want to delete a single procedure without affecting others then simply use the following query.
SELECT 'DROP FUNCTION ' || oid::regprocedure
FROM pg_proc
WHERE oid = {$proc_oid}