Re: MDB_INTEGERDUP in back-mdb's indexer for attr-tables.

Леонид Юрьев wrote: > > Thanks, Howard. > > It would be nice if some clarification, like these, will be in the lmdb.h. MDB_INTEGERDUP is already clearly documented. > > Leonid. > > 2015-05-01 4:42 GMT+03:00 Howard Chu <hyc(a)symas.com&gt;: >> >> 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 >>> tool. >>> 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 >>> 'entryCSN'. >>> >>> 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 >>> test". >>> - all test are passed without MDB_INTEGERDUP. >>> - but you told MDB_INTEGERDUP is necessary >>> >>> So, >>> - how and when MDB_INTEGERDUP will have an impact? >>> - in which cases keys in the table definitely should be sizeof(int) or >>> sizeof(long)? >> >> >> >> 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/ > > -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/