Although Postgres Pro AXE has its own snapshots, Postgres Pro snapshots are still used even for analytical queries that read only the OLAP data from Parquet files holding the transaction horizon. As a result, VACUUM cannot delete dead tuples from heap tables, which over time leads to table bloat and performance degradation.

To avoid holding the transaction horizon, Postgres Pro AXE provides the axe.use_postgres_snapshot configuration parameter. By default, the parameter is set to true, and a Postgres Pro snapshot is used for each query. When the parameter is set to false, any query that works with heap tables fails with an error. This ensures that only queries that do not work with heap tables succeed, and Postgres Pro snapshots are not used.

You can set the axe.use_postgres_snapshot configuration parameter for the current session or globally:

  -- For the current session:
  SET axe.use_postgres_snapshot TO false;

  -- Globally:
  ALTER SYSTEM SET axe.use_postgres_snapshot TO false;