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How Do I Resynchronize a PostgreSQL Primary Key Sequence Out of Sync with Table Rows?

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Release: 2025-01-23 12:09:11
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How Do I Resynchronize a PostgreSQL Primary Key Sequence Out of Sync with Table Rows?

Resolving PostgreSQL Primary Key Sequence Conflicts

Data insertion failures due to duplicate key errors often indicate a primary key sequence out of sync with the table's rows. This typically occurs after database import or restore processes. Here's how to rectify this:

  1. Confirm Sequence Imbalance:

    First, determine the highest existing ID:

    SELECT MAX(id) FROM your_table;
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  2. Examine the Next Sequence Number:

    Next, check the sequence's next value:

    SELECT nextval('your_table_id_seq');
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    If the sequence value is less than the table's maximum ID, synchronization is required.

  3. Begin Transaction:

    Wrap the correction within a transaction for data integrity:

    BEGIN;
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  4. Exclusive Table Lock:

    To prevent concurrent modifications, exclusively lock the table:

    LOCK TABLE your_table IN EXCLUSIVE MODE;
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  5. Adjust Sequence Value:

    Use this command to update the sequence:

    SELECT setval('your_table_id_seq', GREATEST((SELECT MAX(your_id) FROM your_table), (SELECT nextval('your_table_id_seq') - 1)));
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    This sets the sequence to the larger of the table's maximum ID or the current sequence value minus one.

  6. Commit Transaction:

    Finalize the changes:

    COMMIT;
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  7. Release Table Lock:

    The table lock is automatically released after the transaction commits.

Following these steps ensures the primary key sequence aligns with the table data, eliminating future duplicate key errors during insertions.

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