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Questions...
>>>
With the introduction of back_hdb in OpenLDAP 2.2.4, the speed of
adding/deleting directory entries is expected to
be increased. But how about the speed of modify indexed attributes? Is it
still the same as OpenLDAP 2.0..?
<<<
The high write concurrency in back-hdb has been largely defeated by the
syncrepl entryCSN update code, which serializes all modifications in both
back-bdb and back-hdb.
Modifying indexed attributes is slightly improved in OpenLDAP 2.1/2.2 vs
OpenLDAP 2.0 but not to any great extent.
>>>
It seems that back_hdb uses a indexing mechanism directed based on Berkely
DB. How deos this indexing method
compared with the original indexing used in back_bdb, in terms of performance
(or computational complexity)?
<<<
back-hdb is 95% identical to back-bdb. Both use the same indexing mechanism.
>>>
What is the function of bdb_modify_internal?
<<<
Its purpose is already fully described in the comments above it. It
consolidates the attribute value modifications that are needed by both
LDAPModify and LDAPModRdn processing.
>>>
The 'ndn' in bdb_cache_find_ndn means what? Normalized DN?
<<<
Yes.
>>>
In bdb_dn2id_add, the key is set to dn and data is set to id when put into
the database, while
in hdb_dn2id_add, the order is reversed. I do not understand this. Could you
give some hint?
<<<
The back-hdb DN2ID structure uses RDNs, not full DNs. The layout was chosen
to efficiently support hierarchical descent from the root, as well as ascent
from a leaf node. Again, the comments in the code already describe the
content and the purpose of each field. A simplified illustration is available
here http://www.openldap.org/conf/odd-sfo-2003/howard-dev.html although the
actual implementation has evolved from when that paper was written.
-- Howard Chu
Chief Architect, Symas Corp. Director, Highland Sun
http://www.symas.com http://highlandsun.com/hyc
Symas: Premier OpenSource Development and Support