How to diagnose and fix the 3B000 savepoint_exception error code in Postgres.

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The 3B000 error code in PostgreSQL stands for savepoint_exception. This error typically occurs when there is an issue with the use of savepoints in a transaction. Savepoints allow you to set markers within a transaction and roll back to these points without aborting the entire transaction.

To diagnose and fix a 3B000 error, you need to:

  1. Review Transaction Code: Examine the code within your transaction where savepoints are being used. Look for any anomalies in the naming, creation, or release of savepoints.
  2. Check Savepoint Names: Ensure that each savepoint has a unique name within the transaction and that the name follows the identifier naming rules in PostgreSQL.
  3. Verify Savepoint Usage: Make sure that you are not trying to release or rollback to a savepoint that does not exist or has already been released.

Here are some examples and sample code to illustrate common issues and how to fix them:

Example 1: Reusing Savepoint Names

BEGIN;
SAVEPOINT my_savepoint;
-- Some SQL operations
SAVEPOINT my_savepoint; -- This is incorrect as the savepoint name is reused
ROLLBACK TO SAVEPOINT my_savepoint;
COMMIT;

In this example, the second SAVEPOINT my_savepoint; statement will cause a 3B000 error because the savepoint name is being reused. To fix this, ensure that each savepoint has a unique name:

BEGIN;
SAVEPOINT my_savepoint;
-- Some SQL operations
SAVEPOINT my_savepoint2; -- Corrected by using a unique name
ROLLBACK TO SAVEPOINT my_savepoint;
COMMIT;

Example 2: Rolling Back to a Non-Existent Savepoint

BEGIN;
SAVEPOINT my_savepoint;
-- Some SQL operations
RELEASE SAVEPOINT my_savepoint; -- Savepoint is released here
ROLLBACK TO SAVEPOINT my_savepoint; -- This will cause a 3B000 error
COMMIT;

In this case, trying to roll back to a savepoint after it has been released will result in a 3B000 error. To resolve this, remove the rollback or do not release the savepoint before rolling back:

BEGIN;
SAVEPOINT my_savepoint;
-- Some SQL operations
-- RELEASE SAVEPOINT my_savepoint; -- Removed release statement
ROLLBACK TO SAVEPOINT my_savepoint;
COMMIT;

Example 3: Incorrect Savepoint Specification

BEGIN;
SAVEPOINT; -- This is incorrect as it does not specify a savepoint name
-- Some SQL operations
ROLLBACK TO SAVEPOINT my_savepoint;
COMMIT;

This will result in a 3B000 error because the SAVEPOINT command is missing a name. To fix this, provide a valid name for the savepoint:

BEGIN;
SAVEPOINT my_savepoint; -- Corrected by adding a name
-- Some SQL operations
ROLLBACK TO SAVEPOINT my_savepoint;
COMMIT;

When dealing with 3B000 errors, it’s crucial to ensure that savepoints are correctly named and managed within the transaction. For more information on savepoint usage and error codes, you can refer to the official PostgreSQL Documentation on Savepoints and PostgreSQL Error Codes.

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