It would be nice if some clarification, like these, will be in the lmdb.h.
2015-05-01 4:42 GMT+03:00 Howard Chu <hyc(a)symas.com>:
Леонид Юрьев wrote:
> Hi, Howard.
> I would like to refine my question.
> Currently I develop a mdb_chk tool for deep check LMDB-files, like a fsck
> It is needed for us, but let this stay aside for now.
> On some step I plan to check the size of each key in each DBI with
> MDB_INTEGERKEY and/or MDB_INTEGERDUP flags.
> Initially I assumed - if one of these flags is set, the the length of
> all keys must be sizeof(int) or sizeof(long). As will be used the
> corresponding comparison functions (mdb_cmp_int, mdb_cmp_long) , which
> can handle only keys of such sizes.
> But this approach has failed. A dbi-tables created for attr by
> mdb_attr_dbs_open() have MDB_DUPSORT|MDB_DUPFIXED|MDB_INTEGERDUP flags
> and may contain records with a 5-byte keys. For instance as the
> Later you have written that MDB_INTEGERDUP is required.
> Now I do not understand how it all works:
> - MDB_INTEGERDUP is set for attr tables.
> - indexer could create a 5-byte keys.
> - mdb-backend set custom comparison function only for MDB_DN2ID table.
> - under debugger I see that md_dcmp is pointed to the default.
> - assert for key-size in default comparators was not failed while "make
> - all test are passed without MDB_INTEGERDUP.
> - but you told MDB_INTEGERDUP is necessary
> - how and when MDB_INTEGERDUP will have an impact?
> - in which cases keys in the table definitely should be sizeof(int) or
MDB_INTGERKEY means the *keys* must be int/long.
MDB_INTEGERDUP means the *values* must be int/long.
When either flag is set, all of the corresponding (keys|values) in the DB
must be the same size.
The indexer only uses MDB_INTEGERDUP - it doesn't care what size the keys
are, but the values must be (longs in this case).
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/