Hi Team,
We are currently planning a data archival initiative for our production PostgreSQL databases and would appreciate suggestions or insights from the community regarding best practices and proven approaches.
**Scenario:**
- We have a few large tables (several hundred million rows) where we want to archive historical data (e.g., older than 1 year).
- The archived data should be moved to a separate PostgreSQL database (on a same or different server).
- Our goals are: efficient data movement, minimal downtime, and safe deletion from the source after successful archival.
- PostgreSQL version: 15.12
- Both source and target databases are PostgreSQL.
We explored using `COPY TO` and `COPY FROM` with CSV files, uploaded to a SharePoint or similar storage system. However, our infrastructure team raised concerns around the computational load of large CSV processing and potential security implications with file transfers.
We’d like to understand:
- What approaches have worked well for you in practice?
This is how I migrated 6TB of data from an Oracle database to Postgresql, and then implemented quarterly archiving of the PG database:
- COPY FROM (SELECT * FROM live_table WHERE date_fld in some_manageable_date_range) TO STDOUT.
- Compress
- scp
- COPY TO archive_table.
- Index
- DELETE FROM live_table WHERE date_fld in some_manageable_date_range (This I only did in the PG archive process
(Naturally, the Oracle migration used Oracle-specific commands.)
- Are there specific tools or strategies you’d recommend for ongoing archival?
I write generic bash loops to which you pass an array that contains the table name, PK, date column and date range.
Given a list of tables, it did the COPY FROM, lz4 and scp. Once that finished successfully, another script dropped archive indices on the current table, COPY TO and CREATE INDEX statements. A third script did the deletes.
This works even when the live database tables are all connected via FK. You just need to carefully order the tables in your script.
- Any performance or consistency issues we should watch out for?
My rules for scripting are "bite-sized pieces" and "check those return codes!".
Your insights or any relevant documentation/pointers would be immensely helpful.
Index support uber alles. When deleting from a table which relies on a foreign key link to a table which _does_ have a date field, don't hesitate to join on that table.
And DELETE of bite-sized chunks is faster than people give it credit for.
