# 42P07 — Duplicate table or relation definition

> PostgreSQL SQLSTATE 42P07: Duplicate table or relation definition (duplicate_table), source-backed diagnosis and recovery guidance.
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# 42P07 — Duplicate table or relation definition

## At a glance {#at-a-glance}

`42P07` (**duplicate_table**) covers relation-name collisions, conditional skips, and inheritance graph checks. Identify the operation before repairing it.

<!-- BEGIN SQLSTATE FACTS: generated by scripts/generate.py; do not edit -->

| Field | Value |
| --- | --- |
| SQLSTATE | `42P07` |
| Condition | `duplicate_table` |
| Status | `active` |
| Known present by | `7.4` |
| Locked snapshots | `9.0.23, 9.1.24, 9.2.24, 9.3.25, 9.4.26, 9.5.25, 9.6.24, 10.23, 11.22, 12.22, 13.23, 14.24, 15.19, 16.15, 17.11, 18.6, 19beta3` |
| Macros | `ERRCODE_DUPLICATE_TABLE` |
| Aliases | `—` |

<!-- source facts: data/errcodes/42P07.json -->
<!-- END SQLSTATE FACTS -->

## Meaning {#meaning}

Core 18.6 paths report `relation "%s" already exists` for table, sequence, index, and CREATE TABLE AS. These object kinds share the `pg_class` relation namespace, so a same-name object of another relation kind can be the collision. The index path with `IF NOT EXISTS` reports NOTICE `relation "%s" already exists, skipping` and returns without checking that the existing index has the requested definition. Inheritance reuses the code for repeated parents and for `circular inheritance not allowed` with DETAIL `"%s" is already a child of "%s".`

## Diagnosis {#diagnosis}

Capture message, severity, DETAIL, statement, schema, and relation kind. For a name collision, inspect `pg_class` joined to `pg_namespace` and include sequences, indexes, tables, views, and materialized views in the search. For an `IF NOT EXISTS` NOTICE, inspect the existing object's owner, persistence, columns, indexes, and options before treating the migration as satisfied; the source guard is name-based. For inheritance messages, inspect `pg_inherits`, resolve the complete parent list, and distinguish a duplicate parent from a cycle.

## Response {#response}

Use idempotent DDL only when the existing definition is acceptable; otherwise choose a deliberate name or an object-specific migration. A relation-name collision may require adopting the existing object or changing the intended name, while a repeated-parent error requires removing the duplicate parent entry. A cycle requires breaking the parent graph and then verifying `pg_inherits`; renaming alone cannot repair it. Recover an explicit-transaction `ERROR` with a savepoint rollback or transaction rollback before catalog checks; a NOTICE path does not require that recovery.

## Messages {#messages}

Representative variants are:

| Path | Severity | Primary | DETAIL |
| --- | --- | --- | --- |
| relation name collision | `ERROR` | `relation "%s" already exists` | none |
| index `IF NOT EXISTS` collision | `NOTICE` | `relation "%s" already exists, skipping` | none |
| repeated inheritance parent | `ERROR` | `relation "%s" would be inherited from more than once` | none |
| circular inheritance | `ERROR` | `circular inheritance not allowed` | `"%s" is already a child of "%s".` |

## Versions {#versions}

From 7.4 through 18.6 and 19beta3; that catalogue range is not a precise introduction claim. The selected 18.6 paths cover relation-name lookup, index `IF NOT EXISTS`, repeated inheritance parents, and circularity; runtime was not run.

## Related {#related}

- [`42P06`](../42p06/)
- [`42710`](../42710/)
- [`23505`](../23505/)
- [`42P04`](../42p04/)

## Sources {#sources}
- `src.errcodes.42P07.18.6` — `src/backend/utils/errcodes.txt` line 383, fixed at `724edf9bde9d356724ad384a2e196edc3c9f80f7`; SHA-256 `6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba` ([source](https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/utils/errcodes.txt#L383)).

- `src.call.42P07.694fcfd426e95ce13263fb9a` — `src/backend/catalog/heap.c` lines 1194-1196, fixed at `724edf9bde9d356724ad384a2e196edc3c9f80f7`; SHA-256 `e720ee58279590793edd0985b3c910970ef56e7361b8ef92e245370587e02a0e` ([source](https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/catalog/heap.c#L1194-L1196)).
- `src.call.42P07.38d8697cf62c00c05657a6d4` — `src/backend/catalog/index.c` lines 898-901, fixed at `724edf9bde9d356724ad384a2e196edc3c9f80f7`; SHA-256 `98a4156a5c21ae856a3b583b633cdeb578a5b69910386c9f166d69fcb04ba2d0` ([source](https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/catalog/index.c#L898-L901)).
- `src.call.42P07.30cb2a5359e1ec4bea60a466` — `src/backend/commands/tablecmds.c` lines 875-878, fixed at `724edf9bde9d356724ad384a2e196edc3c9f80f7`; SHA-256 `422dc8e833df4940755973c757e338295822ba3e4c7266c40669f49f96eb15a9` ([source](https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/commands/tablecmds.c#L875-L878)).
- `src.call.42P07.19ee2522385544dc7ceb62bb` — `src/backend/commands/tablecmds.c` lines 17376-17381, fixed at `724edf9bde9d356724ad384a2e196edc3c9f80f7`; SHA-256 `422dc8e833df4940755973c757e338295822ba3e4c7266c40669f49f96eb15a9` ([source](https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/commands/tablecmds.c#L17376-L17381)).
- `src.calls.REL_18_6.42P07` — resolved core call groups; SHA-256 `9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf`.
- [`authored evidence`](../data/evidence/42p07.json) — source claims, message roles, and runtime boundary.