Full Table Repacks

To perform a full-table repack, pg_repack will:

1. create a log table to record changes made to the original table

2. add a trigger onto the original table, logging INSERTs, UPDATEs and DELETEs into our log table

3. create a new table containing all the rows in the old table

4. build indexes on this new table

5. apply all changes which have accrued in the log table to the new table

6. swap the tables, including indexes and toast tables, using the system catalogs

7. drop the original table

pg_repack will only hold an ACCESS EXCLUSIVE lock for a short period during

initial setup (steps 1 and 2 above) and during the final swap-and-drop phase

(steps 6 and 7). For the rest of its time, pg_repack only needs

to hold an ACCESS SHARE lock on the original table, meaning INSERTs, UPDATEs,

and DELETEs may proceed as usual.

Index Only Repacks

To perform an index-only repack, pg_repack will:

1. create new indexes on the table using CONCURRENTLY matching the definitions of the old indexes

2. swap out the old for the new indexes in the catalogs

3. drop the old indexes

Creating indexes concurrently comes with a few caveats, please see `the documentation`__ for details.

.. __: http://www.postgresql.org/docs/current/static/sql-createindex.html#SQL-CREATEINDEX-CONCURRENTLY