Download Introduction to Threading in .Net

You Can Do Anything
If You Think “Yukon”
Presented by:
Richard Broida
Senior Architect
Bennett Adelson
Agenda
• Overview of SQL Server 2005
• Enhancements to Database Engine and
T-SQL
• CLR Hosting
– Writing CLR functions, procedures and
triggers
– Creating user-defined data types and
aggregates
• Resources
• Q&A
Bennett Adelson
History of Microsoft SQL Server
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1988
1993
1994
1995
1996
1997
1998
2000
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MS/Sybase version for OS/2
4.21 for NT 3.1
MS/Sybase partnership ends
6.0, major rewrite
6.5
6.5 Enterprise Edition
7.0, total rewrite
2000
Bennett Adelson
SQL Server 2000 Has Lived to See …
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Windows XP and Windows 2003 Server
.NET Framework 1.0 and 1.1
BizTalk 2000, 2002 and 2004
Commerce Server 2000 and 2002
CMS 2000 and 2003
SharePoint 2001 and 2003
Exchange Server 2000 and 2003
Oracle 9i and 10g
DB2 8.1 and 8.2
Bennett Adelson
New Features in SQL Server 2005
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SQLCLR
XML as Native Data Type
Hosting Web Services
Enhancements to T-SQL
Client API Enhancements
Service Broker
Notification Services
Enhanced Reporting Services
Enhanced Analysis Services
Bennett Adelson
SQL Server 2005 Editions
• Express Edition
– Replaces MSCE
– Freely downloadable and redistributable
• Workgroup Edition
– Less expensive than Standard
• Standard Edition
• Enterprise Edition
• Developer Edition
Bennett Adelson
Where is It Now?
• First Technology Preview released at
PDC in October 2003
• Betas 1 and 2 Released in 2004
• Most current version on MSDN is
February 2005 Community Technology
Preview
• A “Beta 3” was announced for April
2005 release, along with Beta 2 of
Visual Studio 2005. Not out yet.
Bennett Adelson
Big Disclaimer
This presentation is based on the February 2005 Community Technology Previews of SQL Server 2005 and Visual Studio 2005. Anything
and everything could change between now and the final release of these products. To the extent of such changes, the information in this
presentation could end up wrong!
Bennett Adelson
Beta/CTP Installation Tips
• Use a clean VM
– Or, completely remove old build before installing new
one using \Setup Tools\Build Uninstall
Wizard\sqlbuw.exe in installation media
• Install SQL Server and Visual Studio on
separate VMs
– They tend to have incompatible builds of the CLR
• Even on separate VMs, not all Yukon/Whidbey
combinations work together. These do:
– Yukon Beta 1 with Whidbey Beta 1
– Yukon Dec CTP with Whidbey Oct CTP
– Yukon Feb CTP with Whidbey Feb CTP
Bennett Adelson
Enhancements to the Database
Engine and T-SQL
Bennett Adelson
Does a SQL Server 2005
Programmer Need to Know T-SQL?
• Absolutely!
– SQLCLR relies on T-SQL for querying and
updating the database
– T-SQL is still the fastest and most powerful
for what it does
– New T-SQL enhancements reduce the
situations where procedural code is
necessary
Bennett Adelson
Enhancements to the Database
Engine
• SNAPSHOT Isolation Level
– Uses versioning instead of locks, like that
“Greek” database
– Can provide better concurrency than
traditional SERIALIZABLE and
READ_COMMITTED
• Large Value Data Types
– VARCHAR(MAX), NVARCHAR(MAX) and
VARBINARY(MAX) can hold up to 231 bytes
– Use instead of TEXT and IMAGE
• Statement-Level Recompilation for SPs
Bennett Adelson
Enhancements to T-SQL
• TRY … CATCH Exception Handling
– With support for Transactions
• OUTPUT Command
– Use with INSERT, UPDATE and DELETE to save copies
of the affected rows in a temporary table
• TOP Command
– Supported in INSERT, UPDATE and DELETE
– Quantity can be a calculated value
• PIVOT command
– Rotates rows into columns and columns into rows
Bennett Adelson
Common Table Expressions
• The “WITH” Clause
– Creates a “virtual” table for use in a single
query
– Often provides a simpler syntax than using
a VIEW or subquery, and may be easier for
Optimizer to optimize
– Allows recursive queries
Bennett Adelson
Simple WITH Clause
WITH BigSales(RepID) AS
(SELECT RepId from Sales WHERE
TotSales > 50000)
SELECT ‘Big Seller’, * FROM SalesReps
WHERE SalesReps.Id = BigSales.RepId
UNION
SELECT ‘Small Seller’, * FROM SalesReps
WHERE SalesReps.Id NOT IN
(SELECT RepId FROM BigSales)
Bennett Adelson
Recursion Example: a “Linked List”
Table: OrgChart
ID
1
2
3
4
5
6
Name
Dubya
Bill
Rama
Sal
Jane
Shu
ReportsTo
NULL
3
1
2
3
1
Bennett Adelson
Query: How Many Levels from the
Top Are You?
Dubya
Rama
Shu
Bill
Jane
Sal
Levels From Top
0
1
1
2
2
3
Bennett Adelson
Performing the Query
WITH LevelsDown (Id, Tot) AS
(
SELECT Id, 0 FROM OrgChart
WHERE ReportsTo is NULL
UNION ALL
SELECT OrgChart.Id, LevelsDown.Tot + 1
FROM LevelsDown JOIN OrgChart
ON LevelsDown.Id = OrgChart.ReportsTo
)
SELECT Name, Tot
FROM OrgChart JOIN LevelsDown
ON OrgChart.ID = LevelsDown.Id
ORDER BY 2
Bennett Adelson
New Ranking Commands
• Require an OVER clause to specify the sorting
order
• ROW_NUMBER
– Inserts a column showing absolute position in the
sort order
• RANK
– Assigns same value to all rows with same rank in the
sort order
• DENSE_RANK
– Like RANK, but doesn’t leave “holes”
• NTILE
– Divides results into equal or near-equal divisions
– Great for efficient paging in a DataGrid
Bennett Adelson
Adding Row Numbers to Query
Output
SELECT ROW_NUMBER()
OVER(ORDER BY LastName)
AS RowNumber,
FirstName, LastName
FROM Person
Bennett Adelson
Selecting the 78th of 83 “Pages” of
Data
SELECT LastName, FirstName FROM
(
SELECT NTILE(83)
OVER (ORDER BY LastName)
AS PageNo,
FirstName, LastName FROM Person
) AS TEMP
WHERE TEMP.PageNo = 78
Bennett Adelson
The SQLCLR
Bennett Adelson
Overview of SQLCLR
• Write Procedures, Triggers and
Functions in .NET languages to run in a
CLR hosted by SQL Server
• Use ADO.NET data access classes to run
T-SQL commands inside the server
• Create User-Defined Data Types that
can be stored in database tables
• Write Aggregate functions to operate on
UDTs
Bennett Adelson
Procedural Database Code before
SQLCLR
• T-SQL
– Clumsy syntax
– Slow when not dealing directly with the database
– Syntax unfamiliar to many programmers
• Extended Stored Procedures
– Write an external DLL in C
– Supported in SQL Server 2005, but likely to be deprecated
• Difficult to develop and test
• Risky, because external DLL runs in SQL Server’s address
space
– Memory leaks
– Database corruption
– Security holes
• External Code in Data Access, Business Logic and/or
Presentation layers
Bennett Adelson
Benefits of SQLCLR
• Write in your favorite .NET language
– Initially supports C#, VB.NET and C++
• Use any .NET development tools
• Use Framework Class Library or other libraries
• Computation-intensive code executes faster
than T-SQL
• Stability and security of the CLR
• Use native SQL security, Code Access Security,
or both
Bennett Adelson
What is a CLR Host?
• Host: Any process that loads the CLR
• .NET Framework 1.x has three hosts:
– Command shell
– IIS
– Internet Explorer
• Can write other CLR hosts using the
Hosting API
• .NET Framework 2.0 expands the
Hosting API to accommodate the needs
of SQL Server
Bennett Adelson
Requirements for Hosting in SQL
Server
• To maximize performance, SQL Server
manages its own memory and threads
without help from the NT Kernel
– SQL Server understands internal memory
needs better than NT Kernel; can use
memory more efficiently with less paging
– SQL Server uses cooperative multitasking to
switch threads without kernel-mode context
switching
• Or in “fiber mode”, SQL Server may use fibers
instead of threads
– Requires multi-CPU machine
Bennett Adelson
How SQL Server Implements CLR
Hosting
• SQLCLR memory management is
handled by SQL Server, not NT Kernel
• SQLCLR threads come from SQL Server
thread pool and are cooperatively
multitasked
– Or if SQL Server is in “fiber mode”, the CLR
threads are actually fibers
• SQLCLR stores assemblies inside the
database and loads them from there,
not from the file system
Bennett Adelson
Permission Sets Defined for SQLCLR
Assemblies
• SAFE
– The default
– Restrictions to assure the stability and security of
SQL Server
• EXTERNAL_ACCESS
– Can access external data sources
• UNSAFE
– No restrictions, except those imposed by .NET
Framework on all managed code
– Similar risks as unmanaged External Stored
Procedures
Bennett Adelson
SAFE Permission Set
• Prohibited to
– Create threads
– Access external resources such file system,
network, registry or environment variables
– Connect to external databases
– Call unmanaged code via PInvoke or RCWs
– Call portions of the Framework Class Library
not marked as safe for SQL Server
• E.g., System.Windows.Forms, System.Security,
System.Reflection
Bennett Adelson
EXTERNAL_ACCESS Permission Set
• Permitted to
– Access external resources such as file
system, network, registry or environment
variables
– Connect to external databases
• Everything else prohibited same as
SAFE
Bennett Adelson
Some Consequences of SQL Server
Hosting
• Static fields must be readonly
• After try{}, a finally{} block is not
guaranteed to be called
Bennett Adelson
How to Install an Assembly in
SQLCLR
• Create the Assembly outside SQL Server
– SQL Server itself comes with no tools to write or
compile assemblies. Can use Visual Studio,
Framework SDK, or other tools
– SQL Server doesn’t need a Strong Name
• Enable SQLCLR on the server
• Install Assembly in SQL Server with CREATE
ASSEMBLY
• Declare a procedure, function or trigger with
CREATE [PROCEDURE|FUNCTION|TRIGGER] …
EXTERNAL NAME …
Bennett Adelson
Enabling SQLCLR on a Server
• CLR Execution is Disabled by Default
– To enable it, execute:
• Sp_configure ‘clr enabled’, 1
• RECONFIGURE
Bennett Adelson
Installing An Assembly
CREATE ASSEMBLY MyAssembly
FROM ‘C:\Projects\bin\MyAssembly.dll’
WITH PERMISSION_SET = SAFE
ALTER ASSEMBLY MyAssembly
FROM ‘C:\Projects\bin\MyAssembly.dll’
WITH PERMISSION_SET = SAFE
DROP ASSEMBLY MyAssembly
Bennett Adelson
Making the Assembly Usable from
T-SQL
CREATE PROCEDURE MyProcedure
(@arg1 int, @arg2 varchar(20))
EXTERNAL NAME
MyAssembly.[MyNameSpace.MyClass].
MyProcedure
CREATE FUNCTION MyFunction
(arg1 int) RETURNS int
EXTERNAL NAME
MyAssembly.[MyNameSpace.MyClass].
MyFunction
Bennett Adelson
Viewing Assemblies in SQL Server’s
Metadata
• To view metadata about assemblies
installed in SQL Server
SELECT * FROM Sys.Assemblies
• To view assembly code itself
SELECT * FROM Sys.Assembly_Files
• To view procedures, functions and
triggers defined from an assembly
SELECT * FROM
Sys.Assembly_References
Bennett Adelson
Demonstration
Creating a SQLCLR Function with
Notepad
Viewing assembly metadata
Bennett Adelson
SQL Database Projects in Visual
Studio 2005
• Allow quick creation of classes for
Stored Procedures, Functions, Triggers,
UDTs and Aggregates
• One-click deployment of assembly into
a database, no need to write T-SQL
code
• SQL Script provided to run while
debugging
Bennett Adelson
Debugging SQLCLR
• Visual Studio 2005 Interactive
Debugger can step through SQLCLR
code
– Must have Visual Studio Remote Debugging
Monitor running on remote SQL Server
• Microsoft has announced intention to
release a free stand alone debugger
sometime after SQL Server 2005 ships
Bennett Adelson
Creating SQLCLR Functions,
Procedures and Triggers
• Must be a static method with one of
– [SqlFunctionAttribute]
– [SqlProcedureAttribute]
– [SqlTriggerAttribute]
• Can belong to a class or struct, whose
name isn’t important
• SQL doesn’t support overloading, so
avoid overloaded method names
Bennett Adelson
Using SQL Data Types in .NET
• SQL types don’t map perfectly to CTS
types
– All SQL types can be NULL, but CTS value
types can never be null
– SQL decimal has a broader range of values
than CTS Decimal
– CTS Float and Double can hold the values
Infinity and NAN, but SQL float and double
cannot
Bennett Adelson
System.Data.SqlTypes
• System.Data.SqlTypes implements
SQL types in .NET
• SqlTypes should be used for
– Parameters to functions and stored
procedures
– Return values from functions
• You can also use SqlTypes in code
outside SQL Server
Bennett Adelson
SqlType Examples
CLR
String
SQLType
SqlString
Int32
Double
Boolean
Byte[]
SqlInt32
SqlDouble
SqlBoolean
SqlBinary
DateTime
Guid
SqlDateTime
SqlGuid
SQL
(n)(var)char,
(n)text
int
float
bit
(var)binary,
image, timestamp
datetime
uniqueidentifier
Bennett Adelson
Operations on SqlTypes
• Numerical SqlTypes support unary and binary
arithmetic operators (+,-,* etc)
• SqlTypes have boolean IsNull property
– Use it instead of comparing a SqlType with CLR null
• SqlTypes support comparison operators
(==,!=,<,> etc), but watch out for special
rules when value = NULL
• SqlTypes have static Null method to create an
instance with value = NULL
• SqlString has concatenation with +
Bennett Adelson
Converting SqlType to CLR Type
void foo( SqlInt32 sqlInt )
{
Int32 clrInt;
clrInt = sqlInt.Value;
// or
clrInt = (Int32)sqlInt;
// but next is error, no implicit conversion
clrInt = sqlInt;
}
Bennett Adelson
Converting CLR Type to SqlType
void foo( Int32 clrInt )
{
SqlInt32 mySqlInt;
mySqlInt = new SqlInt32(clrInt);
// or
mySqlInt.Value = clrInt;
// or
mySqlInt = (SqlInt)clrInt;
// ok, implicit conversion allowed this direction
mySqlInt = clrInt
}
Bennett Adelson
Demonstration
Creating a SQLCLR Function with
Visual Studio 2005
Using SqlTypes
Bennett Adelson
Accessing the Database from
SQLCLR Code
• Database code written in T-SQL
can issue SQL statements like
SELECT, UPDATE and EXEC at any
time
• SQLCLR code must go through an
ADO.NET data provider
Bennett Adelson
The System.Data.SQLServer
Provider (as of Feb 2005 CTP)
• System.Data.SqlServer provides data
access classes for use (only) within
SQLCLR
• Connection objects aren’t needed
• Static SqlContext methods create
commands, DataAdapters, etc
• In SAFE assembly, SQL Server won’t
allow data access unless class has this
attribute property:
DataAccess=DataAccessKind.Read
Bennett Adelson
Changes Coming
• Microsoft announced that in next prerelease of SQL Server 2005,
System.Data.SqlServer will merge into
System.Data.SqlClient
• To connect to the database from within
SQLCLR, you will use a SQLConnection
with this connection string:
“context connection=true”
Bennett Adelson
Data Access Example (Feb CTP)
SqlCommand comm =
SqlContext.CreateCommand();
comm.CommandText = “SELECT *
FROM MyTable”;
SqlDataReader reader =
comm.ExecuteReader();
// use the reader …
Bennett Adelson
Data Access Example (Coming Soon)
SqlConnection conn = new
SqlConnection(“context
connection=true”)
SqlCommand comm = new
SqlCommand()
comm.Connection = conn;
comm.CommandText = “…”;
conn.Open();
// use the command …
Bennett Adelson
Splitting the SqlCommand
• SQLDefinition – the parts of the
command that don’t change in multiple
invocations
• SQLExecutionContext – the parts that
do, such as the parameters
• These can yield better performance
than a single SqlCommand
Bennett Adelson
SqlPipe
• Returns a TDS (tabular data set)
stream to the client
• Use to return the results of stored
procedures to clients
SqlDataReader reader =
command.ExecuteReader();
SqlPipe pipe = SqlContext.GetPipe();
pipe.Send( reader );
Bennett Adelson
Demonstration
Executing SELECT statement
inside a SQLCLR Function
Putting It Together: Selecting a
Random Row from a Table
Bennett Adelson
User-Defined Data Types and
Aggregates
Bennett Adelson
Is SQL Server 2005 an ObjectOriented Database?
• No
– Will not store any arbitrary CLR type in the
database
– Does not support inheritance or
polymorphism
• It will store User-Defined Types, which
emulate native SQL scalar types
• Though created in .NET, UDTs behave
more like SQL types than OOP types
Bennett Adelson
What is a User-Defined Data Type?
• A UDT is a .NET Class or Struct that can
function as a SQL scaler type
• A scaler can be stored in a column of a
table, or be the type of a variable
• Examples of built-in scaler types
– INT
– CHAR
– DATETIME
Bennett Adelson
What Must a Scaler Be Able to Do?
• Mandatory
– Be serializable to/from a byte array
– Be serializable to/from a string
– Be able to equal NULL
• Optional, But Usually Necessary
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–
–
–
Support comparison operators (=,<,>, etc)
Support numerical operators (+,-,*,/ etc)
Support aggregation functions
Be indexable
Bennett Adelson
Creating a UDT
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•
•
Can be a Class or Struct
Must have [SqlUserDefinedAttribute]
Must implement INullable
Must override ToString()
Must have a static Parse() that converts
a string to an instance of the UDT
Bennett Adelson
Binary Serialization of UDTs
• Byte stream cannot exceed 8,000 bytes
• If [SqlUserDefinedAttribute] is set to
Format.Native, SQL Server will handle
serialization
– All UDT fields must be “blittable”
• I.e., fields that are simple value types
– Sort order must be based on order of the
binary fields
• Use Format.Native whenever possible
Bennett Adelson
Format.Native Serialization
[Serializable]
[SqlUserDefinedType
(Format = Format.Native,
IsByteOrdered = true)]
[StructLayout(LayoutKind =
Sequential)]
struct MyUDT
{…}
Bennett Adelson
User-Defined Binary Serialization
[Serializable]
[SqlUserDefinedType(
Format = Format.UserDefined,
IsByteOrdered = true,
IsFixedLength = true,
MaxByteSize = 17)]
struct MyUDT
{…}
Bennett Adelson
UDTs Outside the Database
• Clients outside the database will need
UDT type information when they see a
table with a UDT column, and they
won’t get the info from SQL Server
• You’ll need to deploy the UDT’s
assembly in the client’s folder, in the
GAC, or elsewhere in the probe path
• This leads to possible version conflicts
between assemblies in and out of
database
Bennett Adelson
What is an Aggregate?
• A class or struct whose methods
implement a SQL aggregation function
• The aggregation function can be applied
in a T-SQL statement to a database
column
• Example:
SELECT MyAgg.Sum(MyTable.UDTCol)
FROM MyTable
Bennett Adelson
Creating an Aggregate
• Class or struct must have
[SerializableAttribute]
• Class or struct must have
[SqlUserDefinedAggregateAttribute]
• Must provide four public methods:
–
–
–
–
Init
Accumulate
Merge
Terminate
Bennett Adelson
Aggregate Attribute Properties
• IsInvariantToNulls
– The aggregate ignores null values. The optimizer can
choose not to send nulls.
• IsInvariantToDuplicates
– The aggregate ignores duplicate values. The
optimizer can choose not to send dupes.
• IsInvariantToOrder
– The result is unaffected by the order in which rows
are processed. Optimizer can send them in any order
• IsNullEmpty
– Result is NULL if no rows are passed. Optimizer can
choose not to create an aggregate at all.
Bennett Adelson
Demonstration
Creating a 2D Point Data Type
And a String Aggregator
Bennett Adelson
Microsoft SQL Server Summit 2005
• With Karen Delaney, author of Inside
SQL Server 2000 and Inside SQL Server
2005
– May 17, 2005
Park Center III
6050 Oak Tree Blvd, Suite 300
Independence, Ohio 44131
Event code: 1032271939
– To register call 1.877.673.8368
• Free, but seating limited
Bennett Adelson
Resources on the Web
• SQL Server 2005 Official Site
– http://msdn.microsoft.com/SQL/2005/defau
lt.aspx
• SQLJunkies
– http://www.sqljunkies.com/
• SQL Server 2005 Hands-On Labs Online
– http://msdn.microsoft.com/sql/2005/2005la
bs/default.aspx
Bennett Adelson
Conclusion
• SQL Server 2005 confirms Microsoft’s
ongoing commitment to the product
– Gets closer to parity with rival databases
• SQLCLR has compelling advantages in
some situations
– Intensive computations in memory
– Use of FCL library features
• In other situations, alternative designs,
including T-SQL, may be better
Bennett Adelson
Conclusion
• SQLCLR solutions require care to build
and test
• SQLCLR developers will need mastery of
both SQL and CLR
Bennett Adelson
Q&A
Bennett Adelson