thanks for this explanation Regards, Nicolas Prochazka 2016-03-11 13:10 GMT+01:00 Howard Chu <[email protected]>:
> nicolas prochazka wrote: > >> Hello, >> we are using lmbd in our product as database backend to save big key >> value ( >> 16K ) . >> First at all, lmbd is the best database in performance comparaison ( read >> / >> write) that we have tested. >> >> My question : >> # Databases >> data_dir:/data/cache/data >> lmdb version:LMDB 0.9.16: (August 14, 2015) >> db page size:4096 >> b-tree depath:4 >> branch pages:527 >> leaf pages:29287 >> overflow oages:6659875 >> data items:1331990 >> >> We have a lot of leaf pages, this is due to our big value size. >> When the database is empty, write and read are very fast, >> but when we delete all keys or a big part of keys, write and read (new >> keys) >> becomes very poor in performance ( / 100 ) . >> Is it a normal due to our big values ? >> The only solution we have found is to destroy database file rather than >> deleting keys >> > > Yeah, the page reclaiming algorithm is somewhat simpleminded and large > records can aggravate a fragmentation problem in the DB. Try upgrading to > 0.9.18 first, it may help a bit. > > We'll be experimenting with better reclaiming for LMDB 1.0. > > -- > -- Howard Chu > CTO, Symas Corp. http://www.symas.com > Director, Highland Sun http://highlandsun.com/hyc/ > Chief Architect, OpenLDAP http://www.openldap.org/project/ >
