[Issue 9735] New: [PATCH] try hard to find free space if database cannot grow

https://bugs.openldap.org/show_bug.cgi?id=9735

Issue ID: 9735 Summary: [PATCH] try hard to find free space if database cannot grow Product: LMDB Version: 0.9.24 Hardware: All OS: Linux Status: UNCONFIRMED Keywords: needs_review Severity: normal Priority: --- Component: liblmdb Assignee: bugs@openldap.org Reporter: libor.peltan@nic.cz Target Milestone: ---

Created attachment 851 --> https://bugs.openldap.org/attachment.cgi?id=851&action=edit Patch fixing the issue "try hard to find free space if database cannot grow"

Note: - the issue is the same in version 0.9.70 (git)

Situation: - the database had already grown to its limit (mapsize) in the past - overflow pages are used heavily as stored values are usually several pages long - free space got fragmented

Problem: - attempt to insert new value results in MDB_MAP_FULL despite there is free space available

Cause: there is a heursitic in mdb_page_alloc() that gives up searching for free space chunk if this would take too much time. This is useful when the database can still grow, as it balances performance with space usage. However, if the database can no longer grow, it prevents inserting new values.

Solution: detect early on in mdb_page_alloc() if the database can grow, and if not, let it try hard to search for free space.

Patch: attached