Microsoft SQL Server Administration

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Barnaby Piers Lynch
5 years ago
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1 Micrsft SQL Server Administratin FILESTREAMS David Hksza

2 Mtivatin fr FILESTREAMS Usually, tw appraches when string unstructured/binary data such as AV media files r dcuments Filesystem - the data are stred in the file system and nly addresses are stred in the database pssible transactin cnsistency prblems Database the data are stred in the database (varbinary(max)) significant grwth f the database size FILESTREAM technlgy allws t stre data in the filesystem while the user sees it as if stred in the database Easy embedding int T-SQL cde the user wrks with varbinary(max) clumns transparency Updates t FILESTREAMS clumns in a transactins can be rlled back transactin cnsistency

3 FILESTREAMS Implemented as VARBINARY(MAX) data type Des nt limit size f bject t 2GB (as BLOB type des) Des nt take up space in buffer pl (uses NT FILESTREAMS stred in FILESTREAM filegrups mapped t directries in a file system Supprts failver clustering nly if FILESTREAM filegrups stred n a shared strage Frm user perspective, FILESTREAM is simply a VARBINARY(MAX) clumn with a FILESTREAM attributed

4 Enabling FS FILESTREAM needs t be enabled in SQL Server Cnfiguratin manager in the prperties f the SQL server instance Or SSMS Server Prperties Advanced Or EXEC sp_cnfigurefilestream_access_level, 2 GO RECONFIGURE GO 0 = Disables FILESTREAM supprt fr this instance 1 = Enables FILESTREAM fr Transact-SQL access 2 = Enables FILESTREAM fr Transact-SQL and Win32 streaming access

5 FS-enabled database CREATE DATABASE TestFS ON PRIMARY (NAME = TestFSDB, FILENAME = 'D:\MSSQLData\MSSQL11.NDBI039\MSSQL\DATA\TestFS.mdf'), FILEGROUP TestFSFS CONTAINS FILESTREAM( NAME = TestFSFS, FILENAME = 'd:\temp\share\testfs') LOG ON (NAME = TestFSLOG, FILENAME = 'D:\MSSQLData\MSSQL11.NDBI039\MSSQL\DATA\TestFS.ldf') GO

6 FS structure FS filegrup FS Data Cntainer $FSLOG transactin lg filestream.hdr metadata fr the SQL server Flder fr every table with a FS-enabled clumn Flder fr every FS-enabled clumns

7 FS-enabled table ROWGUIDCOL clumn needed in rder t transparently link BLOBs in the file system with their crrespnding rws in the database tables CREATE TABLE [db].[items]( [ItemID] UNIQUEIDENTIFIER ROWGUIDCOL NOT NULL UNIQUE, [ItemNumber] VARCHAR(20), [ItemDescriptin] VARCHAR(50), [ItemImage] VARBINARY(MAX) FILESTREAM NULL )

8 Manipulating FS with T-SQL AS VARBINARY(MAX) = CAST(bulkclumn AS VARBINARY(MAX)) FROM OPENROWSET( BULK '\\dbrman\share\item.jpg', SINGLE_BLOB ) AS x INSERT INTO Items (ItemID, ItemNumber, ItemDescriptin, ItemImage) SELECT NEWID(), SELECT *, ItemImage.PathName() FROM items

9 Accessing FS data Streaming API (1) OpenSqlFilestream Expsed by the SQL Server Native Client API (part f SQL Server client tls) Allws streaming directly against the file system using the FS handle

10 Accessing FS data Streaming API (1) SqlCmmand sqlcmmand = new SqlCmmand(); sqlcmmand.cnnectin = sqlcnnectin; Try { sqlcnnectin.open(); //The first task is t retrieve the file path f the SQL FILESTREAM BLOB that we want t //access in the applicatin. sqlcmmand.cmmandtext = "SELECT Chart.PathName() FROM Archive.db.Recrds WHERE SerialNumber = 3"; String filepath = null; Object pathobj = sqlcmmand.executescalar(); if (DBNull.Value!= pathobj) filepath = (string)pathobj; else { thrw new System.Exceptin("Chart.PathName() failed t read the path name fr the Chart clumn."); }

11 Accessing FS data Streaming API (2) //The next task is t btain a transactin cntext. All FILESTREAM BLOB peratins ccur within a transactin cntext t maintain data cnsistency. SqlTransactin transactin = sqlcnnectin.begintransactin("maintranactin"); sqlcmmand.transactin = transactin; sqlcmmand.cmmandtext = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()"; Object bj = sqlcmmand.executescalar(); byte[] txcntext = (byte[])bj; //The next step is t btain a handle that can be passed t the Win32 FILE APIs. SqlFileStream sqlfilestream = new SqlFileStream(filePath, txcntext, FileAccess.ReadWrite);

12 Accessing FS data Streaming API (3) byte[] buffer = new byte[512]; int numbytes = 0; //Write the string, "EKG data." t the FILESTREAM BLOB. In yur applicatin this string wuld be replaced with the binary data that yu want t write. string smedata = "EKG data."; Encding unicde = Encding.GetEncding(0); sqlfilestream.write(unicde.getbytes(smedata.tchararray()), 0, smedata.length); //Because reading and writing are finished, FILESTREAM must be clsed. This clses the c# FileStream class, but des nt necessarily clse the the underlying FILESTREAM handle. sqlfilestream.clse(); } //The final step is t cmmit r rll back the read and writeperatins that were perfrmed n the FILESTREAM BLOB. sqlcmmand.transactin.cmmit();

13 Surces

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