Specifies a server-side component that is used by the indexing system to index documents that have the file format that is associated with the IFilter.
Real World Example
A commonly used business application that has a file format that can be saved into Microsoft Office SharePoint Server 2007 does not have built-in support for indexing the file content, and is in a proprietary binary format. An IFilter is installed that allows the system to index, and users to search for, content in these documents.
An IFilter is commonly a DLL that is registered in the indexing service and is called whenever a document is found that matches the assigned document type settings. Several IFilters are already built into Office SharePoint Server 2007 and Windows SharePoint Services 3.0 to index such files as Office system documents.
Any IFilter that is installed in the environment must be installed on every server running indexing services (for example, Windows SharePoint Search, or Office SharePoint Server Search). Additionally, the search properties for the indexed document type must also be updated. Give special attention to any IFilter installation request for the following reasons:
A poorly performing IFilter can have a negative impact on the indexing crawl time in a large environment.
A poorly implemented IFilter can cause a memory leak.
An IFilter cancall a client that allocates memory but does not free it in a timely fashion.
A common request that accompanies the installation of a new IFilter is to also add new document icons.
IFilters, because they are commonly unmanaged code, might not be available in 64-bit versions, which can lead to issues for server farms based on 64-bit Windows Server operating systems.