How to troubleshoot MISMATCHED_SCHEMA Errors in YugabyteDB (Including Hidden DDLs like ALTER ROLE)

Environment

YugabyteDB: All

Applications encounter the following error, often without any explicit DDL (CREATE, ALTER, DROP) operations:

Caused by: com.yugabyte.util.PSQLException: ERROR: The catalog snapshot used for this transaction has been invalidated: expected: <version>, got: <version>: MISMATCHED_SCHEMA

Restarting application pods may not resolve the issue. In some cases, a database restart (pause/unpause) is required.

• Expected case: A DDL operation updates the database catalog version while transactions are in progress, causing version mismatch.
• Less obvious case: Some commands not typically considered DDL (like ALTER ROLE) also modify system catalogs, incrementing the master catalog version.

If application connection pools retain connections with an outdated catalog version, any new query on those connections will fail with MISMATCHED_SCHEMA. This can occur even if auditing is not enabled to log the query.

• Commands such as ALTER ROLE update the database's system catalog.
• The master catalog version increases, invalidating snapshots held by existing connections.
• Connections using the old snapshot will encounter MISMATCHED_SCHEMA errors until they are recycled.

Check t-server logs for catalog version changes, even when auditing is disabled. On the YugabyteDB nodes, run:

grep "incrementing master catalog version" /path/to/tserver.log

Look for entries similar to:

I0524 17:43:28.378070 3531793 pg_client.cc:167] Session id 53692: Session id acquired. Postgres backend pid: 3531793
otho8AutLOG:  YbIncrementMasterDBCatalogVersionTableEntryImpl: incrementing master catalog version (breaking)
otho8AutDETAIL:  Local version: 463, node tag: ALTER ROLE.

• The node tag identifies the operation that triggered the catalog version change.

• Restart Application or Pooler: The primary solution is to ensure all old database connections are dropped and new ones established.
  • If your application manages its own connection pool, restarting the application will typically achieve this.
  • If you are using an external connection pooler (such as PgBouncer or Pgpool-II), you may need to restart the pooler or force it to close all existing backend connections to resolve the error. Restarting only the application pods will not help if the connection pool is external.
• Database Restart (Last Resort): If application/pooler restarts do not help, restart the entire YugabyteDB universe (pause/unpause in YBA). This forcibly drops all connections, but is generally unnecessary if client connection handling is robust.

• Schedule Catalog Changes Carefully: Run operations like ALTER ROLE during maintenance windows or periods of low activity.
• Improve Connection Handling: Ensure applications recycle connections gracefully on errors, especially on MISMATCHED_SCHEMA (SQLSTATE 40001). These errors are safe to retry; see YugabyteDB docs.

• Schema/catalog version mismatches are expected with concurrent DDL and DML.
• The error code is retriable (SQLSTATE 40001).
• Reference for more: YugabyteDB Docs and YugabyteDB Forum.

Reference: SUPPORT-644