- Software and digital services
- Databases
42P01
PostgreSQL 42P01 undefined_table: relation name not resolved
Evidence linked to this decision
View source: PostgreSQL 18 Appendix A: Error CodesRisk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
PostgreSQL returns SQLSTATE 42P01 (undefined_table) when a statement names a table, view, or relation that cannot be found in the target schema or current search_path. Check current_database() and SHOW search_path before running any DDL.
Safety first
Stop and check this first
- Never create an empty dummy table in production just to silence 42P01, and never add a schema writable by untrusted users to search_path, because a malicious user able to create objects in your search path can take control and execute arbitrary SQL functions.
- Note that information_schema.tables only lists tables and views that the current user owns or has some privilege on, so verify existence with the owning role or DBA before assuming a table was dropped.
Safe checks you can perform
- Verify the connected database and effective search_path in the failing session
- Search information_schema.tables and to_regclass across all schemas in the database
- Check whether the missing relation is a session-bound temporary table
Leave these tasks to a qualified professional
- Do not attempt this professional task: Qualify the relation with schema.table or configure role search_path safely
- Do not attempt this professional task: Roll back any failed transaction block and execute the reviewed migration
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Qualify the relation with schema.table or configure role search_path safely
What they doHave the developer or DBA reference the object as schema.table in SQL queries, or configure the role search_path to include only trusted schemas where untrusted users do not hold CREATE privilege.
They must show youthe output of to_regclass and pg_table_is_visible confirming the relation resolves in the session.
In writingthe exact schema.table qualification or ALTER ROLE search_path setting applied and verified.
Roll back any failed transaction block and execute the reviewed migration
What they doWhen the table or view is genuinely absent from the target database, have the DBA issue ROLLBACK on any aborted transaction, verify a recent backup, and run the reviewed migration script to create the relation in the proper schema.
They must show youthe newly created row in information_schema.tables and its non-null OID from to_regclass.
In writingthe migration identifier executed, the target current_database() and table_schema, and the backup timestamp.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Verify the connected database and effective search_path in the failing session
- Who:
- You, your developer, or your DBA running a read-only check with the application's connection parameters.
- How:
- Execute SELECT current_database(), current_schema, current_schemas(true) and SHOW search_path using the same role and connection string (with password redacted).
- Result that matters:
- The exact database name and the ordered array of searchable schemas active in that session.
- If current_database() is not the database where the application schema lives, that confirms a connection routing or environment configuration mistake.
- If current_database() is correct but the application's schema is missing from current_schemas(true), that confirms why unqualified table references fail with 42P01.
- Evidence to keep:
- Save the output of SELECT current_database(), current_schema, current_schemas(true) and SHOW search_path.
Never expose passwords or secrets from the connection string when recording session diagnostics.
Evidence: PostgreSQL 18 system information functions · PostgreSQL 18 schemas
Search information_schema.tables and to_regclass across all schemas in the database
- Who:
- Your developer or DBA checking whether the relation exists under another schema or letter case.
- How:
- Run SELECT table_schema, table_name, table_type FROM information_schema.tables WHERE lower(table_name) = lower('<target_table>') and test SELECT to_regclass('schema_name.table_name').
- Result that matters:
- Every schema containing a table or view with that name, its exact upper/lower case spelling, and its table_type (BASE TABLE, VIEW, FOREIGN, or LOCAL TEMPORARY).
- If the table appears in information_schema.tables under a different table_schema or with mixed-case letters, that confirms the relation exists and needs schema qualification or exact double-quoting.
- If no row appears for an owner or privileged role and to_regclass returns NULL, that confirms the relation has not been created in this database.
- Evidence to keep:
- Record the rows returned from information_schema.tables and the OID result from to_regclass.
Evidence: PostgreSQL 18 lexical structure · PostgreSQL 18 system information functions · PostgreSQL 18 information_schema tables view
Check whether the missing relation is a session-bound temporary table
- Who:
- Your developer reviewing the application transaction flow and connection pool behavior.
- How:
- Check SELECT pg_my_temp_schema() in the session and inspect whether the application creates a temporary table on one pooled connection and queries it on another connection.
- Result that matters:
- Whether pg_my_temp_schema() returns zero (no temporary tables created in this session) while the query expects a temporary table.
- If pg_my_temp_schema() returns zero when the query runs, that confirms the current session never created the temporary table or a connection pool switched backend sessions.
- If the query targets a persistent BASE TABLE or VIEW rather than a temporary relation, that rules out session-temp scoping and points to migration state or schema qualification.
- Evidence to keep:
- Keep the application log sequence showing where CREATE TEMP TABLE and the failing query ran, along with the pg_my_temp_schema() value.
Evidence: PostgreSQL 18 system information functions · PostgreSQL 18 information_schema tables view
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Virtual technician
Does 42P01 still appear after these checks?
This guided flow uses the exact code and your answers to choose a test, an expected result and the next branch.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Software and digital services
- Brand
- PostgreSQL
- Product type
- Databases
Known code variants
- PostgreSQL 42P01
- SQLSTATE 42P01
- undefined_table
What it means
Appendix A assigns 42P01 to undefined_table in Class 42, Syntax Error or Access Rule Violation. A client connection can only access objects in the single database specified when connecting, and unqualified relation names are resolved by searching the schemas in search_path in priority order. If no match is found in search_path, PostgreSQL reports 42P01 even when a table with that name exists in another schema of the database. Because unquoted names fold to lower case while quoted names preserve case, this code alone does not prove the table was dropped; wrong database targets, search_path settings, case quoting, or session-local temporary tables cause the same error.
Warnings and stop conditions
- Highsource verified
Never create an empty dummy table in production just to silence 42P01, and never add a schema writable by untrusted users to search_path, because a malicious user able to create objects in your search path can take control and execute arbitrary SQL functions.
Evidence: PostgreSQL 18 schemas
- Lowsource verified
Note that information_schema.tables only lists tables and views that the current user owns or has some privilege on, so verify existence with the owning role or DBA before assuming a table was dropped.
Evidence: PostgreSQL 18 information_schema tables view
Symptoms and causes
Probable causes · in order
- Unqualified relation resides in a schema not listed in the session search_pathCommon
When a query omits the schema prefix, PostgreSQL searches only the existing schemas in search_path and raises an error if no match is found there, even when the table exists in another schema of the database.
Evidence: PostgreSQL 18 schemas
- Connection points to the wrong database or the schema migration has not runCommon
A client connection can only access data in the single database specified in the connection request, so connecting to a different database or running code before its migration creates the table triggers 42P01.
Evidence: PostgreSQL 18 schemas · PostgreSQL 18 information_schema tables view
- Quoted mixed-case table identifier referenced without matching double quotesPossible
PostgreSQL folds unquoted identifiers to lower case, so a table created as "Orders" is stored with an uppercase O and will not match an unquoted SELECT FROM Orders query.
Evidence: PostgreSQL 18 lexical structure
- Query references a LOCAL TEMPORARY table created in a different sessionPossible
Temporary tables live in a session-specific temporary schema (checked via pg_my_temp_schema and pg_is_other_temp_schema), so another connection from a pool cannot resolve that temporary relation.
Evidence: PostgreSQL 18 system information functions · PostgreSQL 18 information_schema tables view
Sources and technical references
- 1
PostgreSQL 18 Appendix A: Error Codes
PostgreSQL Global Development Group · 2026 · official_doc
- 2
PostgreSQL error and notice fields
PostgreSQL Global Development Group · 2026 · official_doc
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