42725

At a glance

42725 is ambiguous_function: lookup found multiple viable candidates but no best one. The case defines uuid and jsonb overloads and passes an unknown string literal.

Meaning

Overload resolution considers literal type, casts, schema visibility, and signatures. With an unknown literal both candidates remain viable, so the parser reports function %s is not unique; this differs from 42723 (definition collision) and 42883 (no candidate). Inspect visible pg_proc rows and argument types.

Diagnosis

List visible candidates in pg_proc, including their identity arguments and input types, and inspect the inferred type of each literal. Schema qualification narrows visibility but does not choose between overloads.

Response

Cast to the type that matches the business meaning or remove an unintended overload. ::uuid selects the UUID overload here. Do not add casts merely to silence an error: they can change validation and overload behavior. In an explicit transaction, the ambiguity leaves INERROR; roll back or return to a suitable savepoint before retrying. The selected autocommit session remains IDLE.

Observed diagnostics

The fixed parser group is explicit ERROR: function %s is not unique, with the hint Could not choose a best candidate function. You might need to add explicit type casts.

Representative case

The registry creates both overloads, triggers with the unknown literal, then repeats the call with an explicit UUID cast and asserts the result.

CREATE FUNCTION syntax_schema.ambiguous_function(uuid) RETURNS text LANGUAGE SQL AS 'SELECT ''uuid''';
CREATE FUNCTION syntax_schema.ambiguous_function(jsonb) RETURNS text LANGUAGE SQL AS 'SELECT ''jsonb''';
SELECT syntax_schema.ambiguous_function('123e4567-e89b-12d3-a456-426614174000');
SELECT syntax_schema.ambiguous_function('123e4567-e89b-12d3-a456-426614174000'::uuid);

The selected 18.6 and 10.21 runs passed SQLSTATE, severity, state/recovery, repair, cleanup, and isolated-target stop assertions. See case JSON and authored evidence; private manifest and registry hashes are recorded there.

Versions

The locked catalogue contains this condition from the 7.4 presence bound through the listed snapshots. The selected natural case passed on PostgreSQL 18.6 and 10.21; that bounded result does not infer every intermediate release or every source branch.

Related

• 42723
• 42883

Sources

• src.errcodes.REL_18_6 — fixed definition at 724edf9bde9d356724ad384a2e196edc3c9f80f7; SHA-256 6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba (source).
• src.ambiguous-function.18.6 — src/backend/parser/parse_func.c lines 570–577 at 724edf9bde9d356724ad384a2e196edc3c9f80f7; blob SHA-256 48314eab022297478ac4e49786afaff2621ab7b1d7b50e156668cf477961384f (source).
• src.ambiguous-function.10.23 — src/backend/parser/parse_func.c lines 499–506 at 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; blob SHA-256 f1b4af88565ca01dbad2b244cd26b42f34764b3f1343b22a9231e271fb0742f2 (source).
• src.calls.REL_18_6 / src.calls.REL_10_23 — fixed call scans, SHA-256 9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf / 00d16d3eb01b71ccf1b245c8f3102f9d0ec9f36fb02777b8dd1b99fcb263040c.
• manifest.42725 / snippet-registry.42725 — hashes are recorded in evidence/42725.json and each runtime record.

Source evidence

Evidence belongs to the frozen source and runtime versions listed here. It is not a runtime verification of the selected manual version.

• src/backend/utils/errcodes.txt · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• raw/calls/REL_18_6.jsonl · ·
• raw/calls/REL_10_23.jsonl · ·
• src/backend/parser/parse_func.c · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_func.c · REL_10_23 ·
  02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4
• verify/cases/42725/cases.json · ·
• verify/cases/42725/snippets.json · ·

Message templates

function %s is not unique

Could not choose a best candidate function. You might need to add explicit type casts.

Reproduction & repair cases

Recorded runtime evidence

{
  "diagnostic": {
    "text": "function c42725_ambiguous_function_call.ambiguous_function(unknown) is not unique\nLINE 1: SELECT \"c42725_ambiguous_function_call\".ambiguous_function('...\n               ^\nHINT:  Could not choose a best candidate function. You might need to add explicit type casts.",
    "context": null,
    "severity": "ERROR",
    "sqlstate": "42725",
    "table_name": null,
    "column_name": null,
    "schema_name": null,
    "source_file": "parse_func.c",
    "source_line": "577",
    "message_hint": "Could not choose a best candidate function. You might need to add explicit type casts.",
    "datatype_name": null,
    "exception_type": "AmbiguousFunction",
    "internal_query": null,
    "message_detail": null,
    "constraint_name": null,
    "message_primary": "function c42725_ambiguous_function_call.ambiguous_function(unknown) is not unique",
    "source_function": "ParseFuncOrColumn",
    "internal_position": null,
    "statement_position": "8",
    "severity_nonlocalized": "ERROR"
  },
  "repair_value": "uuid",
  "failed_status": "IDLE",
  "repair_status": "IDLE",
  "connection_autocommit": true
}

{
  "diagnostic": {
    "text": "function c42725_ambiguous_function_call.ambiguous_function(unknown) is not unique\nLINE 1: SELECT \"c42725_ambiguous_function_call\".ambiguous_function('...\n               ^\nHINT:  Could not choose a best candidate function. You might need to add explicit type casts.",
    "context": null,
    "severity": "ERROR",
    "sqlstate": "42725",
    "table_name": null,
    "column_name": null,
    "schema_name": null,
    "source_file": "parse_func.c",
    "source_line": "506",
    "message_hint": "Could not choose a best candidate function. You might need to add explicit type casts.",
    "datatype_name": null,
    "exception_type": "AmbiguousFunction",
    "internal_query": null,
    "message_detail": null,
    "constraint_name": null,
    "message_primary": "function c42725_ambiguous_function_call.ambiguous_function(unknown) is not unique",
    "source_function": "ParseFuncOrColumn",
    "internal_position": null,
    "statement_position": "8",
    "severity_nonlocalized": "ERROR"
  },
  "repair_value": "uuid",
  "failed_status": "IDLE",
  "repair_status": "IDLE",
  "connection_autocommit": true
}