EC
42883
PostgreSQLERRORCommonUndefined FunctionHIGH confidence

function does not exist

What this means

The query parser/planner could not find a function (or operator) with the given name and argument type signature in the current search_path. Postgres performs function resolution at parse time using the name and the types of all arguments.

Why it happens
  1. 1Misspelled function name
  2. 2Function exists in a different schema not in search_path
  3. 3Calling a function with incorrect argument types (Postgres overloads by signature)
  4. 4Required extension not installed (e.g., calling uuid_generate_v4() without uuid-ossp)
  5. 5Function was dropped or never created in this database
How to reproduce

A function is called with a wrong name or from a schema not in search_path.

trigger — this will error
trigger — this will error
SELECT uuid_generate_v4(); -- requires uuid-ossp extension

expected output

ERROR:  function uuid_generate_v4() does not exist
LINE 1: SELECT uuid_generate_v4();
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

Fix 1

Install the required extension

WHEN When the function is provided by an extension that is not yet installed.

Install the required extension
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
SELECT uuid_generate_v4();

-- Or use the built-in alternative (Postgres 13+):
SELECT gen_random_uuid();

Why this works

Extensions package functions, types, and operators. CREATE EXTENSION copies the extension's SQL objects into the current database's catalog. After installation, the functions are discoverable in the search_path and the planner can resolve them.

Fix 2

Check function signature and add explicit casts

WHEN When the function exists but is being called with the wrong argument types.

Check function signature and add explicit casts
-- Find matching overloads:
SELECT proname, pg_get_function_arguments(oid)
FROM pg_proc
WHERE proname = 'my_function';

-- Call with explicit cast if needed:
SELECT my_function(42::BIGINT);

Why this works

Postgres function overloading is resolved by matching argument types exactly (after implicit cast consideration). pg_proc stores all function signatures; querying it reveals which overloads exist and what argument types they expect.

What not to do

✕ Add the function's schema to search_path permanently at the database level without review

Expanding search_path can cause name conflicts and unintended function shadowing from attacker-controlled schemas.

Version notes
Postgres 13+

gen_random_uuid() is built-in; no extension needed for UUID generation.

Sources
Official documentation ↗

src/backend/parser/parse_func.c — ParseFuncOrColumn()

Function Type Resolution ↗

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