Re: Need an idea to operate massive delete operation on big size table.

Youness,

Your cut-and-paste ChatGPT contributions to this list reveal a degree of cretinism.

-- Alex

> On Jan 15, 2025, at 10:27 am, youness bellasri  wrote:
> 
> You're absolutely right—PostgreSQL doesn't have a DISABLE clause for indexes or constraints like some other databases (e.g., SQL Server). However, there are still ways to work around this limitation and optimize large delete operations in PostgreSQL. Here are some PostgreSQL-specific strategies:
> 
> 1. **Batch Deletion**: Delete in small chunks using `LIMIT` or `CTE`.
>    ```sql
>    DELETE FROM your_table WHERE  LIMIT 10000;
>    ```
> 
> 2. **Drop and Recreate Indexes**: Drop indexes before deletion, then recreate them.
>    ```sql
>    DROP INDEX idx_name;
>    DELETE FROM your_table WHERE ;
>    CREATE INDEX idx_name ON your_table(column_name);
>    ```
> 
> 3. **Partitioning**: Use table partitioning to drop entire partitions instead of deleting rows.
>    ```sql
>    DROP TABLE your_table_partition_name;
>    ```
> 
> 4. **Archive and Truncate**: Copy rows to keep into a temp table, truncate the original, then reinsert.
>    ```sql
>    CREATE TABLE temp_table AS SELECT * FROM your_table WHERE ;
>    TRUNCATE TABLE your_table;
>    INSERT INTO your_table SELECT * FROM temp_table;
>    DROP TABLE temp_table;
>    ```
> 
> 5. **Disable Triggers**: Temporarily disable triggers during deletion.
>    ```sql
>    ALTER TABLE your_table DISABLE TRIGGER ALL;
>    DELETE FROM your_table WHERE ;
>    ALTER TABLE your_table ENABLE TRIGGER ALL;
>    ```
> 
> 6. **Optimize Settings**: Increase `work_mem` and `maintenance_work_mem` for the session.
>    ```sql
>    SET work_mem = '1GB';
>    SET maintenance_work_mem = '2GB';
>    ```
> 
> 7. **Vacuum and Analyze**: Clean up after deletion.
>    ```sql
>    VACUUM ANALYZE your_table;
>    ```
> 
> 8. **Soft Deletes**: Use an `is_deleted` flag to mark rows for later cleanup.
> 
> By batching, partitioning, and optimizing settings, you can make large deletes faster and less disruptive.
> 
> Le mer. 15 janv. 2025 à 16:22, Ron Johnson  a écrit :
> Sadly, Postgresql does not have (super-handy) "DISABLE" clauses.
> 
> On Wed, Jan 15, 2025 at 10:12 AM youness bellasri  wrote:
> 1. Batch Deletion
> Instead of deleting all records at once, break the operation into smaller batches. This reduces locking, transaction log growth, and the risk of timeouts.
> 2. Use Indexes
> Ensure that the columns used in the WHERE clause of the delete queries are indexed. This speeds up the identification of rows to delete.
> 3. Disable Indexes and Constraints Temporarily
> If the table has many indexes or constraints, disabling them during the delete operation can speed up the process. Re-enable them afterward.
> 
> Le mer. 15 janv. 2025 à 16:08, Ron Johnson  a écrit :
> On Wed, Jan 15, 2025 at 9:54 AM Gambhir Singh  wrote:
> Hi,
> 
> I received a request from a client to delete duplicate records from a table which is very large in size. 
> 
> Delete queries (~2 Billion) are provided via file, and we have to execute that file in DB. Last time it lasted for two days. I feel there must be another way to delete records in an efficient manner
> 
> Maybe the delete "queries" are poorly written.  Maybe there's no supporting index.
> 
> 
> -- 
> Death to , and butter sauce.
> Don't boil me, I'm still alive.
>  lobster!

-- 
Alex Balashov
Principal Consultant
Evariste Systems LLC
Web: https://evaristesys.com
Tel: +1-706-510-6800