PostgreSQL Object Not in Prerequisite State (SQLSTATE 55000)

When PostgreSQL raises ERROR: <message> with SQLSTATE 55000, the condition name is object_not_in_prerequisite_state. This error means the server refused to execute an operation because the target object — a table, index, sequence, replication slot, or similar — is not in the state the operation requires before it can proceed.

What This Error Means

SQLSTATE class 55 is PostgreSQL's "Object Not In Prerequisite State" class, a group of errors that signal an object exists but is not ready for the requested operation. The generic 55000 code is the catch-all condition within that class; more specific sibling codes include 55006 (object in use) and 55P02 (can't change runtime parameter).

PostgreSQL raises 55000 when internal state checks on the target object fail before the operation even starts. The error is raised before any data modification occurs, so the operation is simply not performed — there is no partial work to roll back. The connection and any surrounding transaction remain valid; you do not need to reconnect or abort the transaction unless your application logic requires it.

Common scenarios where PostgreSQL emits a bare 55000 message include running VACUUM or ANALYZE on a table that is currently being processed by autovacuum, operating on a replication slot that is not in the correct state, or interacting with an index or materialized view that has not finished being built.

Common Causes

1. VACUUM or ANALYZE conflicts with autovacuum. If autovacuum already holds a lock on the table and the operation is incompatible, PostgreSQL can surface a 55000-class error rather than simply waiting.

2. Replication slot state mismatch. Attempting to advance, drop, or read from a logical or physical replication slot that is already being consumed by another walsender process, or a slot that has not been fully initialized, triggers this error.

3. Operating on an index that is not yet valid. An index created with CREATE INDEX CONCURRENTLY that did not finish (e.g., was interrupted) remains in an invalid state. Certain operations that depend on a valid, ready index will fail with this error.

4. Materialized view not yet populated. A REFRESH MATERIALIZED VIEW CONCURRENTLY requires the view to have at least one unique index and to have been populated at least once. Attempting the concurrent refresh before the view has any data raises this error.

5. Sequence operations on an uninitialized sequence. Calling setval() or nextval() on a sequence that was created in the same transaction but not yet committed can occasionally produce prerequisite-state failures in edge cases involving temporary sequences or cross-session visibility.

How to Fix object_not_in_prerequisite_state

1. Wait and retry for autovacuum conflicts. Autovacuum sessions are short-lived. If you receive this error while manually running VACUUM, wait a moment and try again, or check pg_stat_activity for active autovacuum workers on the table:

   SELECT pid, query, state, wait_event_type, wait_event
   FROM pg_stat_activity
   WHERE query ILIKE '%autovacuum%';
   

2. Check and clean up replication slots. List all replication slots and their state before operating on them:

   SELECT slot_name, slot_type, active, restart_lsn, confirmed_flush_lsn
   FROM pg_replication_slots;
   

   If a slot is inactive but blocking operations, drop it if it is no longer needed:

   SELECT pg_drop_replication_slot('slot_name');
   

3. Drop and recreate invalid indexes. Find invalid indexes and remove them before recreating:

   SELECT indexrelid::regclass AS index_name, indisvalid
   FROM pg_index
   WHERE NOT indisvalid;
   

   DROP INDEX CONCURRENTLY invalid_index_name;
   CREATE INDEX CONCURRENTLY new_index_name ON table_name (column_name);
   

4. Populate a materialized view before using CONCURRENTLY. Run an initial non-concurrent refresh to populate the view, then switch to concurrent refreshes:

   -- First time: populate the view
   REFRESH MATERIALIZED VIEW my_view;
   
   -- Subsequent refreshes can be concurrent
   REFRESH MATERIALIZED VIEW CONCURRENTLY my_view;
   

   Also ensure the materialized view has a unique index, which is required for CONCURRENTLY:

   CREATE UNIQUE INDEX ON my_view (id);
   

5. Check object state in catalog tables. When the cause is not immediately obvious, inspect system catalog tables for the affected object:

   -- For tables: check relstate (available in some extensions/versions)
   SELECT relname, relkind, relpersistence
   FROM pg_class
   WHERE relname = 'your_table_name';
   

Additional Information

• SQLSTATE class 55 errors are part of PostgreSQL's extended error code scheme. The full class is documented in Appendix A of the PostgreSQL manual.
• Related codes in the same class: 55006 (object_in_use) and 55P02 (cant_change_runtime_param) and 55P03 (lock_not_available).
• This error has been part of PostgreSQL for many major versions. The specific scenarios that trigger it have expanded over time as features like logical replication, concurrent index builds, and concurrent materialized view refreshes were added (PostgreSQL 9.3, 9.4, 9.6, and later).
• Most PostgreSQL drivers (libpq, psycopg2, asyncpg, JDBC) surface this as a DatabaseError or OperationalError with SQLSTATE 55000 in the error metadata. Check the exception's pgcode attribute (Python drivers) or getSQLState() (JDBC) to detect it programmatically.
• 55000 is not a transient network error — a simple reconnect will not resolve it. The underlying object state must be corrected first.

Frequently Asked Questions

Why does VACUUM sometimes raise a 55000 error instead of just waiting? Manual VACUUM and autovacuum can conflict when both target the same table at the same time. In certain situations PostgreSQL will refuse the manual request rather than queue it indefinitely. This is by design: autovacuum will complete its pass quickly, so retrying shortly after is the correct approach.

Can I ignore this error and retry the transaction? The error itself does not leave any partial state, so retrying is safe once the prerequisite condition is met. However, a blind retry loop without first resolving the underlying state issue will continue to fail. Identify why the object is not in the required state and fix that before retrying.

How do I find which object is causing the error? The error message accompanying SQLSTATE 55000 almost always names the object (e.g., ERROR: index "foo_idx" is not yet valid). Capture the full error message from your logs or driver. If the message is not descriptive enough, enable log_error_verbosity = verbose in postgresql.conf to include the CONTEXT and DETAIL fields.

Is SQLSTATE 55000 the same as a lock timeout? No. Lock timeouts produce SQLSTATE 55P03 (lock_not_available). SQLSTATE 55000 means the object's internal state is wrong for the operation, not that another session is holding a conflicting lock. The distinction matters when writing retry logic in application code.