SearchFilter Class

Filters a search to allow only selected documents from an index to be returned.

dtSearch.Engine.SearchFilter

public class SearchFilter : DisposableObject;

Remarks

The SearchFilter object provides a way to designate which documents can be returned by a search. It is useful in situations where a text search using must be combined with another search such as a search of a database. The database search is done first, and then the results of the database search are used to limit the dtSearch search.

For more information on how SearchFilters can be used to improve search efficiency, see:

Limiting searches with SearchFilters

Document Ids

Search filters do not use names to identify documents because a filter may specify thousands, or hundreds of thousands, of documents, and a table of filenames would take too much memory and would take too long to check. Instead, each document is identified by (a) the index it belongs to, and (b) the document's DocId, a unique integer that is assigned to each document in an index.

A DocId that is selected may be returned in search results. A document that is not selected will not be returned in search results, even if it otherwise satisfies the search request.

If the criteria for the SearchFilter can be expressed as one or more search requests, you can use SelectItemsBySearch to select documents in the SearchFilter.

Indexes and Index identifiers

A search filter can cover any number of indexes. To add an index to a search filter, call addIndex() with the full path to the index. The path must be expressed exactly as it will be expressed in the search job. The AddIndex() method returns an integer that is used to identify that index when selecting and de-selecting documents for the filter. (This makes the selection and de-selection functions, which may be called thousands of times, more effiicent.)

Implementation

A search filter is implemented in the dtSearch Engine using a table of bit vectors, one for each index in the filter. Each bit vector has one bit for each document in its index. For example, a search filter for a single index with 1,000,000 documents would have 1,000,000 bits, or 125 kilobytes of data.

IDisposable

SearchFilter requires the IDisposable Pattern.

Topics

Topic	Description
SearchFilter Members	The following tables list the members exposed by SearchFilter.
SearchFilter Methods	The methods of the SearchFilter class are listed here.
SearchFilter Properties	The properties of the SearchFilter class are listed here.

SearchFilter Methods

SearchFilter Methods	Description
AddIndex	Add an index to the filter, returning an integer that can be used to identify the index in the selection functions.
And	Combine this filter with another filter in a logical "AND" operation.
AndNot	Combine this filter with another filter in a logical "AND NOT" operation.
Equals	Compare two SearchFilters for equality.
GetItems	Returns an array of integers containing the document ids of the documents selected in the filter.
Or	Combine this filter with another filter in a logical "OR" operation.
Read	Read the search filter from a disk file.
SelectAll	Select all of the documents in the index.
SelectItems	Set the selection state of a range of document ids, from firstItem to lastItem, to the selection state indicated by fSelected.
SelectItems	Set the selection state of an array of document ids to the selection state indicated by fSelected.
SelectNone	Select no documents in the index.
Write	Save the search filter to a disk file.

SearchFilter Properties

SearchFilter Properties	Description
IndexCount	Returns the number of indexes in the SearchFilter.