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Re: bdb corruption
How did you find your hash buckets and over pages for the objectClass index?
My system returns:
#db_stat -d /usr/local/var/openldap-data/objectClass.bdb
53162 Btree magic number.
9 Btree version number.
2 Minimum keys per-page.
4096 Underlying database page size.
0 Number of levels in the tree.
0 Number of unique keys in the tree.
0 Number of data items in the tree.
0 Number of tree internal pages.
0 Number of bytes free in tree internal pages (0% ff).
0 Number of tree leaf pages.
0 Number of bytes free in tree leaf pages (0% ff).
0 Number of tree duplicate pages.
0 Number of bytes free in tree duplicate pages (0% ff).
0 Number of tree overflow pages.
0 Number of bytes free in tree overflow pages (0% ff).
0 Number of pages on the free list.
Does this mean that my system isn't using the index? I have
index objectClass eq
in my slapd.conf.
Howard Chu wrote:
This 2.5MB number also doesn't take indexing into account. Each indexed
attribute uses another database file of its own, using a Hash structure.
Unlike the B-trees, where you only need to touch one data page to find an
entry of interest, doing an index lookup generally touches multiple keys, and
the point of a hash structure is that the keys are evenly distributed across
the data space. That means there's no convenient compact subset of the
database that you can keep in the cache to insure quick operation, you can
pretty much expect references to be scattered across the whole thing. My
strategy here would be to provide enough cache for at least 50% of all of the
hash data. (Number of hash buckets + number of overflow pages + number of
duplicate pages) * page size / 2.
The objectClass index for my example database is 5.9MB and uses 3 hash
buckets and 656 duplicate pages. So ( 3 + 656 ) * 4KB / 2 =~ 1.3MB.