Sql-Server

Yesterday’s blog post on the need for contracts for stored procedures caused a lot of comments and email. One of the most interesting comments came from Jamie Thomson regarding return values. Jamie’s totally correct on this. Return values should be part of any contract.

I’ve been thinking further about how return values should be incorporated into a contract and initially thought it should be something like this:

CREATE OR ALTER PROCEDURE SomeSchema.SomeSproc (someparameters)

WITH CONTRACT SalesOrderHeaderAndDetails ENFORCED

     (ROWS OrderHeaders(SomeColumn INT, SomeOtherColumn NVARCHAR(50) NULL),

           OrderDetails(AnotherColumn INT, YetAnotherColumn INT, 

                        EvenYetAnotherColumn GEOGRAPHY),

      RETURNS INT,

      EXCEPTIONS NoSuchCustomer(50020,'No such Customer'),

                 DuplicateOrder(50022,'That order already exists')),

     EXECUTE AS (execution options here if needed)

I thought the values could be RETURNS INT or RETURNS NULL, but on reflection (no pun intended), I realized that in many cases it is necessary to resort to documentation to know what a stored procedure return value is. That would be eased if the return value also had a name as part of its metadata. So perhaps a more complete contract would look like:

2010-01-20

One thing that seems confusing to people when they first look at StreamInsight is that there are several development models:

1. Implicit Server

2. Explicit Server

3. IObservable/IObserver 

Implicit server is fairly straightforward. You define your input stream and create a query to consume your output stream. StreamInsight does all of the heavy lifting associated with creating the server, binding your adapters, etc.

Explicit server is the most flexible but the most coding work. You specifically spin up (create and instantiate) a server object, from it spin up an application, register your input/output adapters and create them via a factory and spin up a query binding object. You use the query binding object to bind together your standing query (via a query template) and your input and output adapters. You use this query binding object to then create a query object (an instance of a query) which you then start/stop as required. With the explicit server model, you can get reuse of query templates, adapters, etc. and you can reuse an existing event stream for multiple queries. This model is also how you’d work with a server that’s not hosted in-process if that’s required.

2010-01-19

Increasingly, developers are using tools that try to automate code generation when dealing with databases. Stored procedures have been a thorn in the side of this. Mostly that’s because it’s difficult to obtain the metadata that is really needed.

RowSets

Most automated tools try to work out what rowsets can come back from the sprocs. The Entity Framework, LINQ to SQL and many others use SET FMTONLY ON to try to determine what might come back from the sproc. This is a flawed mechanism as it returns one set of metadata for every potential code path through the sproc. It really only works for the most trivial sprocs ie: single statements that perform basic CRUD operations.

2010-01-19

One of the key decisions you’ll make when working with StreamInsight is the payload that will be carried by each event. Events contain and EventKind (which is related to whether they’re inserting a new event or modifying an existing one), some temporal information (depending upon the EventShape -> Point, Interval or Edge) and a payload that is user-defined.

A payload is defined via a .NET class or struct. In general, a class will be a better option as it ensures field ordering which is likely to be important for generic (vs typed) adapters. StreamInsight ignores anything except public fields and properties and there are limitations on the data types. For example, basic .NET types are permitted but not any of the nested types.

2010-01-16

Another item I had on the Connect site was about pagination. I wanted to be able to restart page numbering within a report. In my case, this was because I wanted to output a set of invoices in a single report but I wanted each invoice to have its own set of page numbers.

This was another item on Connect that came back saying “Done!”

And again, the team went further.

2010-01-13

I’m really happy with the Reporting Services team. I’ve had a few items on Connect where I’ve asked for features and they’ve come back and said “Done!”.

One of these is RenderFormat. I wanted the ability to change my formatting based upon where I was rendering to. For me, this came from a need to have quite different output when rendered to Excel than when rendered to HTML or PDF.

2010-01-13

Continuing on the theme of describing StreamInsight, the next major concept is the Event Model. Events in StreamInsight are made up of two sets of data. One set is the basic information required by the StreamInsight engine such as when an event occurred. The other set is the user data contained within the events, called the “payload”.

You can define what is contained in the payload. It is effectively a .NET class or struct that exposes a set of public members. We’ll talk more about the payload in another post.

2010-01-13

Since I posted some StreamInsight info the other day, I’ve had a bunch of people asking me what StreamInsight is used for.

StreamInsight is Microsoft’s implementation of Complex Event Processing. This is not a new market but it is new territory for Microsoft.

Complex Event Processing (CEP) is all about querying data while it’s still in flight. Traditionally, we obtain data from a source, put it into a database and then query the database. When using CEP, we query the data *before* it hits a database and derive information that helps us make rapid business decisions, potentially also including automated business decisions.

2010-01-11

One of the new items coming with SQL Server 2008 R2 and Visual Studio 2010 is the Data-Tier Application. It is designed for (what are described as) departmental applications.

What a “deparmental” application is deserves some thought. Mostly it relates to the size of the application. What percentage of your databases (count of databases not their volume) would be under say 2GB? What about 10GB? The argument is that for most sites, it’s a surprisingly high percentage. Even most sites I see at the Enterprise level have one or two very large databases and the rest are fairly small. Does that apply to your sites?

2010-01-09

While building content for the upcoming Metro training for SQL Server 2008 R2, Bill Chesnut and I were puzzled about the Adjust option for AdvanceTimePolicy in the AdvanceTimeSettings for a stream. It was described in Books Online as causing the timestamp for the event to be adjusted forward to the time of the latest CTI (current time increment). No matter what we tried though, we couldn’t seem to get it to do anything.

2010-01-09