42846 — Cannot coerce

At a glance

42846 is cannot_coerce: no applicable cast connects the source and target types. The selected expression asks for integer to date.

Meaning

The fixed primary is cannot cast type %s to %s. It is not 22P02 (a bad value for a valid cast) or 42804 (an expression type mismatch in a target context). Inspect pg_cast and the expression context; the selected autocommit connection remains IDLE after the impossible cast.

Diagnosis

Read both source and target types from the diagnostic and inspect pg_cast and the expression context. Confirm whether the application needs a typed literal or a documented conversion function.

Response

Construct a value in the target type or use a documented conversion function. The case uses DATE '2026-01-01'; it does not invent an integer-to-date business mapping or hide input errors with NULLIF. In an explicit transaction, the failed cast leaves INERROR; roll back or return to a suitable savepoint before retrying. The selected autocommit path returns to IDLE.

Observed diagnostics

The selected parse_expr.c group is explicit ERROR with primary cannot cast type %s to %s and no detail or hint.

Representative case

The registry evaluates SELECT 1::integer::date, then a date-typed literal and asserts the exact returned date.

SELECT 1::integer::date;
SELECT DATE '2026-01-01';

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

• 22P02
• 42804

Sources

• src.errcodes.REL_18_6 — fixed definition at 724edf9bde9d356724ad384a2e196edc3c9f80f7; SHA-256 6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba (source).
• src.cannot-coerce.18.6 — src/backend/parser/parse_expr.c lines 2782–2787 at 724edf9bde9d356724ad384a2e196edc3c9f80f7; blob SHA-256 63c37770872a08978f931c31f801666a08e3bc8e51c2c65ff60151a1d139d55b (source).
• src.cannot-coerce.10.23 — src/backend/parser/parse_expr.c lines 2739–2744 at 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; blob SHA-256 2700ba4a37d0715b66be76c900c7da7cf6a4d818eb71178e7b9a51e48e59e136 (source).
• src.calls.REL_18_6 / src.calls.REL_10_23 — fixed call scans, SHA-256 9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf / 00d16d3eb01b71ccf1b245c8f3102f9d0ec9f36fb02777b8dd1b99fcb263040c.
• manifest.42846 / snippet-registry.42846 — hashes are recorded in evidence/42846.json and each runtime record.