How to diagnose and fix the 55000 object_not_in_prerequisite_state error code in Postgres.

The 55000 object_not_in_prerequisite_state error in PostgreSQL indicates that an operation has been attempted on an object that is not in the appropriate state for the requested action. This error can occur in various scenarios, such as trying to modify an object that is currently being used by another session or attempting an action that is not allowed in the current transaction state. To diagnose and fix this error, consider the following possibilities and solutions:

  1. Modifying a View or Materialized View:
    Attempting to update, delete, or insert into a view or a materialized view will result in this error because these objects are not directly modifiable.
   -- Incorrect: Trying to insert into a view
   INSERT INTO my_view (column1) VALUES ('value1');

   -- Correct: Insert into the underlying table instead
   INSERT INTO my_table (column1) VALUES ('value1');

For materialized views, you can refresh them if needed:

   REFRESH MATERIALIZED VIEW my_materialized_view;
  1. Using a Sequence:
    Trying to execute a CURRVAL call on a sequence before a NEXTVAL call has been made in the current session will trigger this error because the sequence’s state has not been initialized with a NEXTVAL call.
   -- Incorrect: Calling CURRVAL before initializing the sequence with NEXTVAL
   SELECT CURRVAL('my_sequence');

   -- Correct: Initialize the sequence with NEXTVAL before calling CURRVAL
   SELECT NEXTVAL('my_sequence');
   SELECT CURRVAL('my_sequence');
  1. Concurrent Access to Advisory Locks:
    If you’re using advisory locks, trying to release a lock that hasn’t been acquired will result in this error.
   -- Incorrect: Trying to release a lock that wasn't acquired
   SELECT pg_advisory_unlock(12345);

   -- Correct: Acquire the lock before releasing it
   SELECT pg_advisory_lock(12345);
   SELECT pg_advisory_unlock(12345);
  1. Transaction State Issues:
    Performing certain operations when the transaction is in an incorrect state, such as trying to commit or rollback a transaction when there is no transaction block, can cause this error.
   -- Incorrect: Trying to commit when not in a transaction block

   -- Correct: Start a transaction block before committing
   -- Perform some operations
  1. Dropping or Modifying Database Objects:
    Attempting to drop or alter a database object that is currently in use by another session can also lead to this error. For example, trying to drop a table while another session is querying it.
   -- Incorrect: Dropping a table while it's being used by another session
   DROP TABLE my_table;

To fix this, you need to ensure that no other sessions are using the table before attempting to drop it. You can check for active connections to the table using the pg_stat_activity view and, if necessary, terminate the relevant connections.

  1. Refreshing Materialized Views Concurrently:
    Attempting to REFRESH MATERIALIZED VIEW CONCURRENTLY without a unique index can cause this error because PostgreSQL requires a unique index to perform a concurrent refresh.
   -- Incorrect: Trying to refresh concurrently without a unique index

   -- Correct: Create a unique index before refreshing concurrently
   CREATE UNIQUE INDEX my_materialized_view_idx ON my_materialized_view (id);

For more information on PostgreSQL error codes, including 55000, you can refer to the PostgreSQL documentation on error codes.

When faced with the 55000 object_not_in_prerequisite_state error, carefully review the context in which the error occurred and check your SQL code for any operations that might conflict with the state of the database objects involved. Adjust your operations accordingly to ensure that objects are in the correct state before you attempt to perform actions on them.

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