How to diagnose and fix the 2200H sequence_generator_limit_exceeded error code in Postgres.

The 2200H error code in PostgreSQL, which stands for sequence_generator_limit_exceeded, occurs when a sequence exceeds its maximum value. Sequences in PostgreSQL are used to generate unique identifiers, typically for a serial column in a table. When you try to increment a sequence beyond its set maximum value, PostgreSQL will raise this error.

To diagnose and fix this error, you need to:

  1. Identify the Sequence: Determine which sequence has reached its maximum value. This is usually indicated in the error message itself.
  2. Alter the Sequence: If the sequence’s maximum value is too low and you need higher values, you can alter the sequence to increase its MAXVALUE.
  3. Restart the Sequence: If the sequence should not exceed its current maximum value but you need to reuse numbers (e.g., after deleting rows), you can restart the sequence with a new START value.

Here are some examples and sample code to help you fix the 2200H error:

Example 1: Increasing the Sequence’s Max Value

If your sequence has reached its maximum value and you want to increase the maximum, you can alter the sequence:

ALTER SEQUENCE your_sequence_name MAXVALUE 9223372036854775807;

Replace your_sequence_name with the actual name of your sequence, and 9223372036854775807 with the desired maximum value (which should not exceed the maximum value for a bigint).

Example 2: Restarting the Sequence

If you’ve deleted rows and want to restart the sequence from a specific number, you can reset the sequence:

ALTER SEQUENCE your_sequence_name RESTART WITH 1;

Replace 1 with the value you want the sequence to start from.

Example 3: Setting NO MAXVALUE

If you don’t want your sequence to have a maximum value, you can alter it to have no max value:

ALTER SEQUENCE your_sequence_name NO MAXVALUE;

This will allow the sequence to continue incrementing until it reaches the maximum value allowed by the data type (bigint, by default).

Remember to choose a strategy that fits your application’s needs. If you’re using sequences for primary keys, it’s generally best to increase the maximum value to avoid running out of unique identifiers.

For more information on the 2200H error code and sequences in PostgreSQL, you can refer to the official PostgreSQL documentation or other resources that explain how to fix sequence-related issues.

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