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Understanding and Using Persistent Search

Novell Cool Solutions: Feature
By Jim Sermersheim, Vithalprasad Gaitonde

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Posted: 3 Mar 2003

Here's an excellent article that explains, "in English", what all the fuss is about this new RFC submitted to ITEF that's titled, "Persistent Search: An LDAP Change Notification Mechanism".

Even though this technology is still in proposal form, you can use it today in eDirectory. Novell Senior Software Engineer, Jim Sermersheim and Novell Software Consultant Vithalprasad Gaitonde explain this technology and show how to put it to work in this AppNote.

Here's how to get to the full article:

If you're not convinced yet, here's a taste of what's being served:

Here's the relevant data that you can specify when performing a Persistent Search:

  • changeTypes. This lets you specify the types of changes you're interested in. For example, you may want to know whenever an entry is added or deleted, but you don't care if any of its attributes get changed. The changeTypes field is a logical OR of one or more of the following values: add (1), delete (2), modify (4) and modDN (8).

  • changeOnly. This is a Boolean field that tells the server whether or not you're interested in the initial result set. If ChangesOnly is True, the server will not return the result entries until modifications occur. If it's False, you get all the entries (as you normally do with a search operation), then entries repeatedly trickle in as they are updated. It's helpful to understand that there are really two phases to a Persistent Search operation: (1) the normal search phase, and (2) the "events" phase. The latter phase is where the server is done sending the initial result set, and is waiting for updates to happen in order to send them back to the client.

  • returnECs. ECs refers to "Entry Change Notifications" (explained below). If this is set to True, the server will send an Entry Change Notification control with each SearchResultEntry returned as a result of the changes.

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