> I think the real solution to this problem is to avoid use of > GetTransactionSnapshot(), and instead use GetLatestSnapshot(). As far > as I can see, that should completely close the hole. This requires > patching IndexBuildHeapRangeScan() to allow for that.
Actually I think there's another problem: if a transaction starts and inserts a tuple into the page range, then goes to sleep, and then another session does the summarization of the page range, session 1 is seen as "in progress" by session 2 (so the scan does not see the new tuple), but the placeholder tuple was not modified either because it was inserted later than the snapshot. So the update is lost. I think the only way to close this hole is to have summarize_range() sleep until all open snapshots are gone after inserting the placeholder tuple and before acquiring the snapshot, similarly to how CREATE INDEX CONCURRENTLY does it. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
