How to Read in a Plain Text File Into R for Text Mining

Introduction

In most cases, we will use clustered and non-clustered indexes to help a query go faster, but these kinds of indexes have their ain limitations and cannot be used for fast text lookup. For instance, a LIKE operator will lead SQL Server to scan the whole table in social club to pick up values that meet the expression adjacent to this operator. This means it won't be fast in every example, fifty-fifty if an alphabetize is created for considered column.

Microsoft SQL Server comes upwards with an answer to role of this consequence with a Full-Text Search feature. This feature lets users and application run graphic symbol-based lookups efficiently by creating a particular type of index referred to every bit a Full-Text Index. This alphabetize tin can exist congenital on the top of one or more columns for a particular tabular array. These columns tin be of post-obit information types:

• char,
• varchar,
• nchar,
• nvarchar,
• text,
• ntext,
• image,
• xml,
• varbinary(max)
• FILESTREAM

The building and usage of Full-Text indexes is always performed in a specific language context like English language or French.

In the following sections, we will first take some fourth dimension to empathize overview how a Full-Text Search characteristic works. In this office, nosotros will ascertain some concepts and utilise them to understand how a Full-Text Index is built and maintained. We'll fifty-fifty go through an illustrative example. Once we are done with theoretical aspects, nosotros'll and so focus on some practical aspects in society to use and maintain this feature: we will see how to create a Full-Text indexed tabular array, how to list out which tables take a Full-Text index and on which columns and much more

Concepts

Definitions

Now that we know what the purpose of Full-Text Search characteristic is, let's invest some fourth dimension in the understanding of how it works. This will assistance the states manage this feature.

Notice that, already at SQL Server installation, nosotros can tell that this feature is special equally the installer defines a daemon service chosen "fdhost.exe". This procedure will be referred in following every bit the "filter daemon host".

It is started by a service launcher called MSSQLFDLauncher for security concerns. It will exchange data with SQL Server service (sqlservr.exe) via shared memory or a named pipe. Fdhost.exe process will access, filter and tokenize user data in lodge to actually build Full-Text indexes. Information technology's likewise called to clarify Full-Text queries, including word breaking and stemming (come across beneath for more info).

This ways that the unabridged Full-Text Search characteristic is spread across these 2 processes: fdhost.exe and sqlserv.exe and that some components of this characteristic interact with each other's. Let's review these components:

• User tables – (sqlserv.exe) – tables for which a full-text alphabetize exists.
• Full-Text gatherer – in sqlserv.exe – a thread responsible for scheduling and driving index population so equally for monitoring.
• Thesaurus files – (sqlserv.exe)– files that incorporate synonyms of search terms.
• StopLists – in sqlserv.exe – objects that contain list of mutual words that can be ignored as they are non significant for a lookup (eastward.g. « and », « or », « but »)
• Query Processor thread – (sqlserv.exe)– thread that compiles and executes T-SQL queries and send Full-Text search to the Full-Text Engine twice: once at compilation and one time during query execution. The query results is matched against the full-text index.
• Full-Text Engine – (sqlserv.exe)– can be seen as office of the Query Processor. It compiles and runs full-text queries and takes stoplists and thesaurus files into account earlier sending back results sets for these queries.
• Full-Text Indexer – (sqlserv.exe)– This thread builds the structure used to store alphabetize tokens.
• Filter Daemon Manager – (sqlserv.exe)– this thread monitors the status of the fdhost.exe daemon service.
• Protocol Handler Thread – (fdhost.exe) – this thread pulls data from memory for farther processing and accesses data from a user table.
• Filters – (fdhost.exe) – they are specific by document blazon and allow the extraction of text data from diverse data types like varbinary, image or xml. They volition be used, for example, in order to remove any embedded formatting on the text of a MS Word certificate. You tin can run following query in guild to get an overview of the filters defined past default:

  EXEC sp_help_fulltext_system _components 'filter' ;

• Discussion breakers and stemmers (fdhost.exe) – Each language has its set of word breakers. These components help to observe the boundaries of each give-and-take in a sentence based on lexical rules of its associated language. So they help tokenizing sentences. Moreover, each word billow is used in pair with a stemmer component. This component helps to discover the root of a verb (its inflectional course) and conjugates verb, also based on language-specific rules. For instance, it will consider all these forms equally being the same: "writing", "wrote", "writer" are all forms of the word "write". Words identified by either of these components are inserted as keywords into a full-text index.

Architecture of a Full-Text Alphabetize

First of all, we have to know that any full-text alphabetize is stored into what Microsoft calls a " full-text itemize". It'south like a container for Full-Text indexes. Why did Microsoft define a logical container for Full-Text indexes? Merely because these indexes are usually split across multiple internal tables that are chosen full-text index fragments. These fragments are created as we insert or update records.

Nosotros can get back data almost a Full-Text Index using dynamic management views and functions. One of these is the sys.dm_fts_index_keywords_by_document function. It returns a data set with the following columns:

• A hexadecimal representation of the keyword
• A human-readable representation of the keyword
• The identifier of the column discipline to a Full-Text Index
• The identifier of the document or the row from which the current keyword has been indexed
• The number of times this keyword has been establish in that document or row indicated by previous column

Here is a sample results set:

In that results set, we can see that for document with identifier "14536", there are 3 occurrences of "%)" keyword.

This allows us to tell that a Full-Text index is an "inverted index" as it'due south generated from a given data source and maps the results of this generation back to its data source. We can too detect that it computes statistics on the fly virtually the occurrence count. If we cheque Full-Text DMVs documentation, we'll discover that these statistics can be obtained:

• by certificate,
• by property,
• past keywords.

This means that a Full-Text alphabetize is not really comparable to a normal alphabetize. But information technology's not the only deviation:

• We can define merely ane Full-Text index per table while we tin ascertain multiple ones for normal indexes.
• Adding information to a Total-Text index is referred to as population. In contrast to normal indexes, these populations are not part of a transaction. This means that even though the information has been inserted in a Full-Text indexed table, which happens in one case the transaction that inserts these data is committed, this does not necessarily mean that the Full-Text index has been updated. Total-Text index population is asynchronous.
• In that location is no grouping of normal indexes into an index catalog.

How a Total-Text Index is populated

As index population is asynchronous, what tells SQL Server it'due south time to actually kickoff a population? There is actually an option that is chosen "Change Tracking", which can be configured by Full-Text Alphabetize and has several possible values:

• Motorcar: asks SQL Server to track data changes for a table and automatically requestsindex population
• MANUAL: asks SQL Server to track data changes for a tabular array only permit user himself request for index population. This means that there could exist hours or days before the Full-Text is updated
• OFF: means that SQL Server won't track data changes and maintenance of this alphabetize is performed totally manually. On systems using this feature extensively, this mode could somewhen require large maintenance windows as population would have to check read all the table.

You will find beneath a diagram that summarizes the fashion a Full-Text Index has to exist populated (for the first time or based on user activity) with only one new or updated record.

There is one important thing to notice: index population is initiated by sqlserv.exe and the population is actually performed past fdhost.exe. As discussed above, this population won't happen every time a user created or changed a tape in a Full-Text indexed tabular array. Instead, when change tracking is in AUTO mode, information technology's the Full-Text Gatherer thread (inside sqlserv.exe) that will tell fdhost.exe to showtime alphabetize population. This is part of the explanation why index population procedure is not synchronous with data modifications.

Total-Text Index population by example

Let's say we accept a table called MyDocs with two columns, 1 called DocId that uniquely identifies a record and ane chosen Comments that contains a comment on the document in plain text, so information technology's a VARCHAR column.

Let's at present assume this table has three records in as follows:

DocId	Comments
1	All-time volume ever on Full-Text Alphabetize
ii	Absurd resources on indexes and tables
3	Cool workshop on Full-Text

At present, let's say that nosotros already created a Full-Text Index on that tabular array and SQL Server decided that it'south time to populate information technology.

Information technology will first take intendance of the row with one equally value for DocId column. It volition tokenize the contents of Comments cavalcade and start to build an index fragment that maps the each token to this tape similar this:

Keyword	DocId
all-time	1
book	1
always	ane
on	1
full-text	1
index	1

It will then cut "full-text" into "full" and "text" and remove the "on" keyword as information technology's a stop word we'll have following keywords list:

Keyword	DocId
best	1
book	1
ever	1
Full	1
full-text	1
index	1
Text	1

Note: Detect that the alphabetize is build using alphabetical ordering

It will do the same with the 2nd document so that the keywords list will be composed of: "cool" , "indexes", "resources" and "tables". It will then analyze the Comments column for the third document and build following keywords listing: "cool", "Total-Text", "Total", "Text" and "workshop".

The results of the analysis for each document could lead to the cosmos of an alphabetize fragment. If we put them together, we have following list of keywords:

Keyword	DocId	#Occurrences
all-time	ane	1
book	i	ane
Cool	two,3	two
ever	1	1
Full	1,3	2
full-text	1,iii	2
index	one	i
Indexes	2	ane
Resource	2	1
Tables	two	1
Text	1,3	2
Workshop	3	1

The list in a higher place would exist the actual data stored in our Total-Text index as the table was empty. You can bank check that this is actually what you get by running the code in the Appendix A of this article. Merely, information technology'south recommended to read all this article before going straight to this appendix!

How to create a table with Full-Text enabled

Allow's say we have a table called [dbo].[DM_OBJECT_FILE] already created using following statement.

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CREATE TABLE [ dbo ] . [ DM_OBJECT_FILE ] ( [ FILE_ID ] [ int ] Non NULL , [ FILE_FIN ] [ int ] NOT Cypher , [ FILE_TITLE ] [ Varchar ] ( 255 ) , [ OBJ_ID ] [ int ] NOT Cipher , [ FILE_ATT ] [ smallint ] NOT Goose egg , [ FILE_PATH ] [ Varchar ] ( 500 ) Cypher , [ FILE_EXT ] [ Varchar ] ( 50 ) NULL , [ FILE_TXT ] [ varbinary ] ( max ) NULL , [ FILE_KEYWORDS ] [ Varchar ] ( m ) NULL , [ FILE_STATUS ] [ smallint ] NULL , [ FILE_TXT_SIZE ] [ Int ] default 0 , [ OBJ_FILE_IDX_DOCTYPE ] [ Varchar ] ( iii ) Aught , CONSTRAINT [ PK_DM_OBJECT_FILE ] PRIMARY Fundamental Clustered ( [ FILE_ID ] ) )

Each file imported into that table is uniquely identified past FILE_ID column, FILE_TXT cavalcade refers to the contents of this file and OBJ_FILE_IDX_DOCTYPE refers to the kind of document that is stored in the FILE_TXT cavalcade.

Now, we are willing to create a Total-Text Index on this table. This means that Full-Text feature should already be installed on our instance. To check whether it'southward the case or not, we can utilise the post-obit query:

SELECT Case FULLTEXTSERVICEPROPERTY ( 'IsFullTextInstalled' ) WHEN i THEN 'Full-Text installed.' ELSE 'Full-Text is Not installed.' END ;

If it appears that Full-Text is not installed, you should consider to install it get-go.

As presently as you are certain that Full-Text feature is installed, we should bank check that FullText search is enabled for the database where our tabular array is stored. We can check information technology with the following statement:

SELECT is_fulltext_enabled FROM sys . databases WHERE database_id = DB_ID ( )

We should go following output:

If we don't, we should run following T-SQL statement:

exec sp_fulltext _database 'enable' ;

But this is not the end! We also want to cheque if there is already a total-text catalog, which is a virtual database object that does non vest to whatever filegroup and refers to a group of Full-Text indexes. To do so, we will run the post-obit query:

select * FROM sys . fulltext _catalogs

If this query did non return any row, then we have to create one or more fulltext catalogs and set one of them as default. To perform this action, nosotros will utilize a argument based on CREATE FULLTEXT CATALOG equally follows:

CREATE FULLTEXT CATALOG FullTextCatalog Every bit DEFAULT ;

At present, we are ready to create the Total-Text alphabetize on [dbo].[DM_OBJECT_FILE] table. To create such an index we have to have some information:

• What is the key index to be used in order to uniquely place records?
• What columns should be part of the alphabetize? (Hither: FILE_TXT column will be used)
• What blazon of document does the column stand for and in which column this data is stored? (Hither: OBJ_FILE_IDX_DOCTYPE cavalcade will be used)
• Which language is used in this column or is it preferable to be totally neutral regarding language estimation?
• Do we enable change tracking and permit the index update past itself or do nosotros manage this part ourselves?

Y'all will find below the create statement for a Total-Text Index on FILE_TXT column from tabular array dbo.DM_OBJECT_FILE, with neutral language interpretation, automatic update and no terminate list.

CREATE FULLTEXT Alphabetize ON dbo . DM_OBJECT_FILE ( FILE_TXT Type COLUMN OBJ_FILE_IDX_DOCTYPE LANGUAGE 0 ) KEY Alphabetize PK_DM_OBJECT_FILE WITH CHANGE_TRACKING = Machine , STOPLIST = OFF ;

How to change the configuration of a Total-Text Index

In that location is a T-SQL command called Modify FULLTEXT INDEX that allows us to perform some operations on a Total-Text Index like:

• Enable or disable the index
• Enable or disable change tracking for Full-Text Alphabetize population. If it stays enabled, nosotros can tell SQL Server whether to automatically schedule an alphabetize population based on user activity or to let us do it manually.
• Add, alter or edit the list of columns that should be office of the Full-Text Index.
• Command index population (only useful when nosotros did not enabled change tracking in automated manner)

For further details, please refer to Microsoft's documentation page.

How to use a Full-Text Alphabetize in queries

Once everything is in identify, our Full-Text Index is created on our table and we can showtime using it with built-in functions. Post-obit functions are predicate functions. This ways that it returns a Boolean value that tin be used in a WHERE clause.

Role Name	Explanation
CONTAINS	Searches for precise or fuzzy (less precise) matches to single words and phrases, words within a sure distance of one another, or weighted matches in SQL Server. Appropriate types of lookups: Give-and-take or phrase Prefix A discussion near another Synonyms Etc. Example usage: SELECT * FROM dbo . DM_OBJECT_FILE WHERE CONTAINS ( FILE_TXT , 'blabla' );
FREETEXT	Searches for values that match the pregnant and not just the verbal wording of the words in the search condition. This function will: tokenize its lookup text in the same way a Full-Text alphabetize is populated (using discussion breaking and stemming, removing cease words). Each token is assigned a weight. then it will generate a list of expansions and replacement keywords based on the thesaurus. Finally, it will compare the list of keywords in the Total-Text index and those that it listed in social club to generate a Boolean value that volition exist returned. Example usage: select * FROM dbo . DM_OBJECT_FILE WHERE FREETEXT ( FILE_TXT , 'zzz' )
CONTAINSTABLE	Same lookup as CONTAINS function except that information technology returns a table of rows with following columns: Central : the values for matching key columns in a Full-Text indexed table RANK : the RANK column is a value (from 0 through 1000) for each row indicating how well a row matched the pick criteria. Simple case usage: await for "blabla" or "huh" select * FROM CONTAINSTABLE ( dbo . DM_OBJECT_FILE , FILE_TXT , 'blabla OR huh' ) Club Past RANK desc
FREETEXTTABLE	Returns a table of zip, 1, or more rows for those columns containing character-based data types for values that lucifer the meaning, simply not the verbal wording, of the text in the specified column. Simple case usage: await for "blabla" or "huh" select * FROM FREETEXTTABLE ( dbo . DM_OBJECT_FILE , FILE_TXT , 'blabla OR huh' ) Gild Past RANK desc

Here is a comparing in terms of the number of results between CONTAINSTABLE and FREETEXTTABLE predicates using the example usage above.

Firstly, the results of CONTAINSTABLE:

Secondly, the results of FREETEXTTABLE:

As we can see, for the get-go one, we get back but 13 rows and ranking value is non that high while the second returns 17 rows more than and ranking values are higher. Furthermore, we can cheque that the ordering of keys is different: The key 16575 is at the fourth position in the commencement screen capture while it'south at the second position in the second one.

These predicate functions tin exist used extensively and are not limited to stock-still lookups. Instead, there is extensive grammer functionality associated to its lookup parameter. On each documentation page for these functions, we will notice the definition of a <contains_search_condition> in the part's grammatical definition. If we look closely at this grammer, we can come across that it'southward very rich and we take to learn this in guild to become the nearly power out of Full-Text Search feature!

1 two 3 4 v 6 seven 8 9 10 11 12 thirteen fourteen xv 16 17 eighteen xix 20 21 22 23 24 25 26 27 28 29 xxx 31 32 33 34 35 36 37 38 39 twoscore 41 42 43 44 45 46 47 48 49 l

< contains_search_condition > :: = { < simple_term > | < prefix_term > | < generation_term > | < generic_proximity_term > | < custom_proximity_term > | < weighted_term > } | { ( < contains_search_condition > ) { { AND | & } | { AND Non | & ! } | { OR | | } } < contains_search_condition > [ . . . n ] } < simple_term > :: = { word | "phrase" } < prefix term > :: = { "discussion*" | "phrase*" } < generation_term > :: = FORMSOF ( { INFLECTIONAL | THESAURUS } , < simple_term > [ , . . . n ] ) < generic_proximity_term > :: = { < simple_term > | < prefix_term > } { { { About | ~ } { < simple_term > | < prefix_term > } } [ . . . n ] } < custom_proximity_term > :: = NEAR ( { { < simple_term > | < prefix_term > } [ ,…n ] | ( { < simple_term > | < prefix_term > } [ ,…n ] ) [ , < maximum_distance > [ , < match_order > ] ] } ) < maximum_distance > :: = { integer | MAX } < match_order > :: = { TRUE | FALSE } < weighted_term > :: = ISABOUT ( { { < simple_term > | < prefix_term > | < generation_term > | < proximity_term > } [ WEIGHT ( weight _value ) ] } [ , . . . n ] )

Moreover, other functions returning a table have been added starting SQL Server 2012. These are:

• semantickeyphrasetable
• semanticsimilaritydetailstable
• semanticsimilaritytable

Looking for information related to the Full-Text feature

How to get the list of supported languages

Nosotros can run post-obit query in social club to get back the listing of supported languages and their linguistic communication identifier:

SELECT * FROM sys . fulltext_languages Lodge Past lcid

Here is a sample of the results ready:

How to get the listing of Full-Text indexes in a item database

Permit's say we want to listing out which tables and columns are used with the Full-Text feature. To do so, nosotros tin run the following query:

1 2 3 iv 5 six 7 8 9 10 11 12 13 xiv 15 16 17 18 19 twenty 21 22 23 24 25 26 27 28 29 xxx 31 32

SELECT SCHEMA_NAME ( tbl . schema_id ) as SchemaName , tbl . name Every bit TableName , FT_ctlg . name AS FullTextCatalogName , i . proper name As UniqueIndexName , scols . proper name Every bit IndexedColumnName FROM sys . tables tbl INNER Join sys . fulltext_indexes FT_idx ON tbl . [ object_id ] = FT_idx . [ object_id ] INNER JOIN sys . fulltext_index_columns FT_idx_cols ON FT_idx_cols . [ object_id ] = tbl . [ object_id ] INNER Bring together sys . columns scols ON FT_idx_cols . column_id = scols . column_id AND FT_idx_cols . [ object_id ] = scols . [ object_id ] INNER JOIN sys . fulltext_catalogs FT_ctlg ON FT_idx . fulltext_catalog_id = FT_ctlg . fulltext_catalog_id INNER JOIN sys . indexes i ON FT_idx . unique_index_id = i . index_id AND FT_idx . [ object_id ] = i . [ object_id ] ;

Here is a sample results:

How to bank check the results of a Full-Text parsing

There are 2 ways to check how Total-Text characteristic parses a given text depending on the source of the text.

Source of the text is a String

If you want to cheque fast what keywords you would get for a detail cord, you might want to utilize sys.dm_fts_parser built-in office.

Here is an example of call to that office.

• The first parameter is the cord that has to be parsed.
• The 2d parameter is the linguistic communication identifier. Hither, it'southward set to 0, which means it's neutral.
• The hhird parameter is the identifier of the stoplist. Here no stoplist is used.
• The final parameter tells this office whether to exist sensitive or not to accents. Here, we asked for insensitivity.

In other words, this part will take the information you would provide when creating a Full-Text Alphabetize.

select * from sys . dm_fts_parser ( '" dsolkjfdskljfsd dfsd-MMM-236.127 dojfdslfkjds"' , 0 , NULL , 0 ) ;

Here are corresponding results. Nosotros can see that from this simple line, we become multiple keywords generated:

Source of the text is a Full-Text Index

If a table is already created with a Full-Text alphabetize, we would use some other dynamic management function (DMF) called sys.dm_fts_index_keywords which takes as a parameter:

• The database identifier in which it should look at
• The object identifier in that database

It returns a dataset with a hexadecimal representation of the keyword, its corresponding form in the manifestly text, the identifier of the column in which the keyword has been found and finally the number of documents where this keyword tin can exist found.

Yous volition find below a T-SQL query to become back keywords found by Total-Text characteristic in our dbo.DM_OBJECT_FILE tabular array so as its results set.

select * From sys . dm_fts_index_keywords ( DB_ID ( ) , OBJECT_ID ( 'dbo.DM_OBJECT_FILE' ) )

How to maintain Full-Text Indexes with alter tracking in Machine mode

If you lot are DBA, you lot tin can't neglect the question of maintenance for these particular indexes that are Full-Text indexes. Except for large systems, I call back there is no reason to gear up change tracking to another mode than Car. That'south the reason why nosotros will only cover this mode.

Actually, it'due south difficult to get good recommendations about the way we should do this. For example, I haven't establish a dominion from Microsoft that says "if at that place is x% fragmentation then reorganize, if it'southward more than 30% then rebuild the index", which is the common guideline for normal alphabetize maintenance.

After reading the paragraph above, in that location are questions that should emerge:

• How practice nosotros rebuild a full-text index?
• Can a Full-Text index be fragmented?
• If so, how could we get some details on this?
• One time we have details on this, how to determine when it's necessary to take cosmetic actions?

How to reorganize or rebuild a particular Full-Text alphabetize?

There is no capability to reorganize or rebuild a given Total-Text index except by dropping and recreating it, using DROP FULLTEXT Index and CREATE FULLTEXT Index commands.

However, let's remember that these indexes are grouped into a logical container called a Total-Text itemize. While we can't rebuild or reorganize a particular alphabetize, we can exercise it on a Total-Text itemize using ALTER FULLTEXT Itemize T-SQL command.

ALTER FULLTEXT CATALOG catalog_name { REBUILD [ WITH ACCENT_SENSITIVITY = { ON | OFF } ] | REORGANIZE | AS DEFAULT }

Can a Full-Text alphabetize be fragmented?

The answer to this question is pretty obvious as we said that, past design, the Full-Text index is built using index fragments created during alphabetize population (or index crawl). This means that, aye, Full-Text indexes can suffer fragmentation and a high fragmentation volition obviously take a direct impact on application performances.

How to check for Full-Text index fragmentation?

Microsoft provides a prepare of management tables or views that we can query in club to get an overview of Full-Text index fragmentation. These are:

• sys.fulltext_catalogs in club to get the listing of Full-Text Catalogs
• sys.fulltext_indexes in order to get the listing of Full-Text Indexes
• sys.fulltext_index_fragments in club to get the listing of index fragments

We can combine information from these management objects in guild to get back an overview of:

• Which indexes are in which Full-Text Itemize?
• How much infinite is consumed past a Total-Text Index?
• On which object a Full-Text Index in based?
• How of import the fragmentation is (in size (Mb) and percent)

This tin be performed using the following query, which is an adaptation of the i published by Geoff Patterson on StackExchange:

ane 2 3 iv 5 half-dozen 7 8 nine 10 11 12 13 14 fifteen sixteen 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

WITH FragmentationDetails Equally ( SELECT table_id , COUNT ( * ) As FragmentsCount , Convert ( DECIMAL ( 9 , 2 ) , SUM ( data_size / ( 1024. * 1024. ) ) ) AS IndexSizeMb , CONVERT ( DECIMAL ( 9 , two ) , MAX ( data_size / ( 1024. * 1024. ) ) ) As largest_fragment_mb FROM sys . fulltext_index_fragments GROUP BY tabular array _id ) SELECT DB_NAME ( ) AS DatabaseName , ftc . fulltext_catalog_id As CatalogId , ftc . [ name ] AS CatalogName , fti . change_tracking_state AS ChangeTrackingState , fti . object_id AS BaseObjectId , QUOTENAME ( OBJECT_SCHEMA_NAME ( fti . object_id ) ) + '.' + QUOTENAME ( OBJECT_NAME ( fti . object_id ) ) AS BaseObjectName , f . IndexSizeMb Equally IndexSizeMb , f . FragmentsCount AS FragmentsCount , f . largest_fragment_mb As IndexLargestFragmentMb , f . IndexSizeMb - f . largest_fragment_mb Equally IndexFragmentationSpaceMb , Instance WHEN f . IndexSizeMb = 0 THEN 0 ELSE 100.0 * ( f . IndexSizeMb - f . largest_fragment_mb ) / f . IndexSizeMb Stop Equally IndexFragmentationPct FROM sys . fulltext_catalogs ftc Bring together sys . fulltext_indexes fti ON fti . fulltext_catalog_id = ftc . fulltext_catalog_id Join FragmentationDetails f ON f . table_id = fti . object _id ;

Hither is a sample outcome. For image readability, rows have been carve up into two sets:

When do we demand to accept corrective actions?

I haven't seen whatsoever recommendations nearly this on Microsoft's documentation website just hither are the results of my searches:

• Based on the researches of Geoff Patterson, he defined that a Full-Text Index needs to be rebuilt starting at 10% of fragmentation.
• In his blog post, Barry Kind suggests to reorganize the Full-Text catalog when 30 to l fragments per table are reached.

There are some tests that have to be done in order to observe the right ready of criteria merely they won't be covered by this article.

Next commodity in this series:

• How to automatically maintain Total-Text indexes and catalogs

Appendix A – code to create testing.MyDocs table

You lot will discover below the T-SQL instructions that will allow you lot to cheque the results nosotros announced in section Total-Text Index population by example.

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create schema testing ; Drop Table testing . MyDocs ; create table testing . MyDocs ( DocId INT IDENTITY ( ane , i ) NOT NULL CONSTRAINT PK_MyDocs PRIMARY KEY , Comments VARCHAR ( MAX ) ) ; insert into testing . MyDocs ( comments ) values ( 'Best book ever on Full-Text Index' ) , ( 'Absurd resources on indexes and tables' ) , ( 'Cool workshop on Full-Text' ) ; CREATE FULLTEXT INDEX ON testing . MyDocs ( Comments LANGUAGE 1033 /* English */ ) KEY INDEX PK _MyDocs ; select * From sys . dm_fts_index_keywords_by_document ( DB_ID ( DB_NAME ( ) ) , OBJECT_ID ( 'testing.MyDocs' ) ) -- where document_id = 3 ; select * From sys . dm_fts_index_keywords ( DB_ID ( DB_NAME ( ) ) , OBJECT_ID ( 'testing.MyDocs' ) ) -- cleanups DROP TABLE testing . MyDocs Drib SCHEMA testing ;

• Writer
• Contempo Posts

Living in Kingdom of belgium, I obtained a chief degree in Figurer Sciences in 2011 at the University of Liege.

I'm ane of the rare guys out there who started to piece of work as a DBA immediately after his graduation. So, I work at the university hospital of Liege since 2011. Initially involved in Oracle Database administration (which are nevertheless under my charge), I had the opportunity to learn and manage SQL Server instances in 2013. Since 2013, I've learned a lot almost SQL Server in administration and development.

I like the chore of DBA considering yous need to have a general knowledge in every field of IT. That's the reason why I won't terminate learning (and share) the products of my learnings.

View all posts past Jefferson Elias

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Source: https://www.sqlshack.com/hands-full-text-search-sql-server/

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