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addpartial Overlay README
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This package contains an OpenLDAP overlay called "addpartial" that
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intercepts add requests, determines if the entry exists, determines what
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attributes, if any, have changed, and modifies those attributes. If the
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entry does not exist, the add request falls through and proceeds normally.
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If the entry exists but no changes have been detected, the client receives
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LDAP_SUCCESS (I suppose it is debatable what to do in this case, but this is
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the most clean for my use. The LDAP_SUCCESS lets me know that the entry I
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sent slapd == the entry already in my slapd DB. Perhaps this behavior
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should be configurable in the future).
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When a change is found, the addpartial overlay will replace all values for
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the attribute (if an attribute does not exist in the new entry but exists
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in the entry in the slapd DB, a replace will be done with an empty list of
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Once a modify takes place, the syncprov overlay will properly process the
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change, provided that addpartial is the first overlay to run. Please see
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the CAVEATS for more specifics about this.
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The addpartial overlay makes it easy to replicate full entries to a slapd
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instance without worrying about the differences between entries or even if
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the entry exists. Using ldapadd to add entries, the addpartial overlay can
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compare about 500 records per second. The intent of the addpartial overlay
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is to make it easy to replicate records from a source that is not an LDAP
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instance, such as a database. The overlay is also useful in places where it
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is easier to create full entries rather than comparing an entry with an
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entry that must be retrieved (with ldapsearch or similar) from an existing
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slapd DB to find changes.
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The addpartial overlay has been used in production since August 2004 and has
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processed millions of records without incident.
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A Makefile is included, please set your OPENLDAP_SRC directory properly.
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After compiling the addpartial overlay, add the following to your
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moduleload /path/to/addpartial-overlay.so
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# after database directive...
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# this overlay should be the last overlay in the config file to ensure that
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# it properly intercepts the add request
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- In order to ensure that addpartial does what it needs to do, it should be
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the last overlay configured so it will run before the other overlays.
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This is especially important if you are using syncrepl, as the modify that
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addpartial does will muck with the locking that takes place in the