At Tue, 26 Jul 2022 12:41:07 +0000, "James Pang (chaolpan)" <chaol...@cisco.com> wrote in > How to make it fast ? These are our steps about copy large data from Oracle > to Postgres > > 1. Create table in Postgres 2. Extract data from Oracle to CSV 3. Alter > table set xxx unlogged, 4. Run copy command into Postgres db 5. Alter > table set xxx logged 6. Create index … > Step 5 took long time ,especially for large tables.
As others pointed, the step5 inevitably requires WAL emittion. On the other hand, there is a proposed patch [1]. It lets ALTER TABLE SET LOGGED/UNLOGGED evade duping the whole target table and could reduce the amount of WAL to be emitted (caused by the difference of tuple-based WAL and per-page WAL) (in major cases). Could you try it and see if it works for you in any extent? regards. [1] https://commitfest.postgresql.org/38/3461/ -- Kyotaro Horiguchi NTT Open Source Software Center
