Maybe that a simple check of the asof_timestamp value like:
asof_timestamp >= now() - time_travel_period
AND
asof_timestamp >= latest_table_ddl
would permit to raise a warning or an error message saying that query result
can not be garanteed with this asof_timestamp value.
latest_table_ddl being found with
SELECT greatest( max(pg_xact_commit_timestamp( rel.xmin )),
max(pg_xact_commit_timestamp( att.xmin ))) as latest_table_ddl
FROM pg_catalog.pg_attribute att
INNER JOIN pg_catalog.pg_class rel
ON att.attrelid = rel.oid WHERE rel.relname = '<asof_tablename>' and
rel.relowner= ...
(tested with add/alter/drop column and drop/create/truncate table)
Regards
PAscal
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