BRIN: Prevent the heapblk overflow during index summarization on very large tables resulting in an infinite loop - Mailing list pgsql-hackers

Previously, heapBlk was defined as an unsigned 32-bit integer. When incremented

by pagesPerRange on very large tables, it could wrap around, causing the condition

heapBlk < nblocks to remain true indefinitely — resulting in an infinite loop.

This could cause the PostgreSQL backend to hang, consuming 100% CPU indefinitely

and preventing operations from completing on large tables.

The solution is straightforward — the data type of `heapBlk` has been changed

from a 32-bit integer to a 64-bit `BlockNumber` (int64), ensuring it can safely

handle extremely large tables without risk of overflow.

This was explained very nicely by Tomas Vondra[1] and below two solutions were

suggested.

     i)  Change to int64

     ii) Tracking the prevHeapBlk

 Among these two I feel using solution #1 would be more feasible(similar to previously used solution 4bc6fb57f774ea18187fd8565aad9994160bfc17[2]), though

 other solution also works.

I’ve attached a patch with the changes for solution #1.
Kindly review it and share your feedback or suggestions — your input would be greatly appreciated.

 Reference:

    [1] https://www.postgresql.org/message-id/b8a4e04c-c091-056c-a379-11d35c7b2d8d%40enterprisedb.com

    [2] https://github.com/postgres/postgres/commit/4bc6fb57f774ea18187fd8565aad9994160bfc17