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SQLServer Full-Text Search


Full-Text Search

Full-Text Engin

“Full-text search allows fast and flexible indexing for keyword-based query of text data stored in a SQL Server database. Unlike the LIKE predicate, which only works on character patterns, full-text queries perform a linguistic search against this data, operating on words and phrases based on rules of a particular language.” [3]

Architecture

“Unlike other SQL operations, Full Text Searching is not managed by the MSSQL Server service. Instead, a new service, Microsoft Search, must be installed and started.”

SQLserver 2000 and 2005

usage of the microsoft search

SQLserver 2008

(from MSDN) “The Full-Text Engine is responsible for reading from and writing to full-text indexes, which are now stored in SQL Server. The Full-Text Engine supports the following:

Indexing
The Full-Text Engine performs a variety of indexing tasks, among them gathering data from the base table and sending the data to the filter daemon host for processing. The filter daemon host filters and tokenizes data provided by the full-text gatherer. After the data has been filtered and the words have been broken, the SQL Server process receives the results and indexes them as an inverted index structure that is stored in database as an internal table. 

Querying
The Full-Text Engine processes full-text search queries and determines which entries (rows or documents) in the base table meet the full-text selection criteria. For each entry that meets the selection criteria, it returns the identity of each row along with an optional ranking value. This information is used to construct the query-result set.” 

Full Text Search Architecture (from Msdn)

Step 1: Gather Indexes : Crawler theads in the (sqlservr.exe)

Step2: Filer deamon host (fdhost.exe) word breaker and indexer

Step 3: Query procesor (sqlservr.exe)

reference:

[1] http://msdn.microsoft.com/en-us/library/ms142587.aspx

[2] http://msdn.microsoft.com/en-us/library/ms142541.aspx

[3] http://msdn.microsoft.com/en-us/library/ms345119(v=sql.90).aspx

[4] http://ditch.developpez.com/sqlserver/fulltext/

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