Tuesday, 13 March 2012

Full Text Search Service

SQL Server Abounding Argument Chase account is a specialized indexing and querying account for baggy argument stored in SQL Server databases. The abounding argument chase basis can be created on any cavalcade with appearance based argument data. It allows for words to be searched for in the argument columns. While it can be performed with the SQL LIKE operator, application SQL Server Abounding Argument Chase account can be added efficient. Abounding allows for inexact analogous of the antecedent string, adumbrated by a Rank amount which can ambit from 0 to 1000 - a college rank agency a added authentic match. It additionally allows linguistic analogous ("inflectional search"), i.e., linguistic variants of a chat (such as a verb in a altered tense) will additionally be a bout for a accustomed chat (but with a lower rank than an exact match). Proximity searches are additionally supported, i.e., if the words searched for do not action in the arrangement they are defined in the concern but are abreast anniversary other, they are additionally advised a match. T-SQL exposes appropriate operators that can be acclimated to admission the FTS capabilities.6465

The Abounding Argument Chase agent is disconnected into two processes - the Filter Daemon action (msftefd.exe) and the Chase action (msftesql.exe). These processes collaborate with the SQL Server. The Chase action includes the indexer (that creates the abounding argument indexes) and the abounding argument concern processor. The indexer scans through argument columns in the database. It can additionally basis through bifold columns, and use iFilters to abstract allusive argument from the bifold balloon (for example, back a Microsoft Chat certificate is stored as an baggy bifold book in a database). The iFilters are hosted by the Filter Daemon process. Once the argument is extracted, the Filter Daemon action break it up into a arrangement of words and easily it over to the indexer. The indexer filters out babble words, i.e., words like A, And etc., which action frequently and are not advantageous for search. With the actual words, an astern basis is created, advertence anniversary chat with the columns they were begin in. SQL Server itself includes a Gatherer basic that monitors changes to tables and invokes the indexer in case of updates.66

When a abounding argument concern is accustomed by the SQL Server concern processor, it is handed over to the FTS concern processor in the Chase process. The FTS concern processor break up the concern into the basic words, filters out the babble words, and uses an built-in album to acquisition out the linguistic variants for anniversary word. The words are again queried adjoin the astern basis and a rank of their accurateness is computed. The after-effects are alternate to the applicant via the SQL Server process.66

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