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Category: Stored Procedures

Temporary Stored Procedures

Jana Sattainathan discusses temporary stored procedures:

The real benefit of these procedures is when they contain lot of logic that you need on a temporary basis but do not want to clutter the existing stored procedure list. You could even have multiple temporary procedures that call each other. I would not go overboard with this. It is just a convenience.

I don’t often see these in use; when I’ve seen them, they’re in environments in which normal stored procedure create rights are locked down and you want to do something as a one-off (like testing an operation against production data).  In other words, those sketchy things that we don’t admit to each other that we do…

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Replication Raiserror Procedure Change

Matt Slocum documents a change to a replication stored procedure in SQL Server 2014 SP2:

I ran into this replication error the other day and I was completely stumped.
Procedure or function sp_MSreplraiserror has too many arguments specified.
 
We started getting that error message shortly after we had applied SP2 for SQL Server 2014 to a server that is a replication Publisher (source of replicated data).

We dug into the commands that were being replicated and found that there were missing rows in the table on the replication Subscriber (destination for replicated data).  Once the rows were populated the errors stopped.  However, after digging in a bit more, we found that this error has an explainable source.

Read on for Matt’s solution to the issue.

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Naming Procedures

Aaron Bretrand shares rules that he uses when naming stored procedures:

I’ve talked about this in my live sessions, but this is an extreme case that really happened – a team took over a week to fix a bug in a stored procedure, and the delay was caused solely by poor naming standards. What happened was that the application was calling dbo.Customer_Update, but the team was hunting for the bug in a different procedure, dbo.Update_Customer. While there was no formal convention in place, the real problem was inconsistency – a consultant charged with writing a different application didn’t check for an existing procedure, she just looked for dbo.Update_Customer in the list; when she didn’t find it, she wrote her own. The bug itself wasn’t crucial, but that lost time can never be recovered.

I’ll repeat again that the convention you choose is largely irrelevant, as long as it makes sense to you and your team, and you all agree on it – and abide by it. But I am asked frequently for advice on naming conventions, and for things like tables, I’m not going to get into religious arguments about plural vs. singular, the dreaded tblprefix, or going to great lengths to avoid vowels. But I think I have a pretty sensible standard for stored procedures, and I am always happy to share my biases even though I know not everyone will agree with them. Again, I touched on this in my earlier post, but sometimes these things bear repeating and a little elaboration.

I agree with this:  pick a standard and stick to it.

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Fork Bombs

Brent Ozar creates a fork bomb in SQL Server:

I’ve always found fork bombs funny because of their elegant simplicity, so I figured, why not build one in SQL Server?

In order to do it, I needed a way to spawn a self-replicating asynchronous process, so I built:

  1. A stored procedure

  2. That creates an Agent job

  3. That runs the stored procedure

I didn’t think it was possible.  I certainly didn’t think it would take a half-dozen lines of code.

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Stored Procedure Last Run Times

Richie Lee has a script to see when stored procedures were last executed:

Quick script to get the last time a stored procedure was executed in the database. The reason for the seemingly over-engineered script is that different query plans can be generated, meaning that stored procedures can appear more than once in the list.

The query doesn’t quite work as-is, but making qs.execution_count into an aggregation and removing it from the GROUP BY would work.  I’d probably rewrite it to look a bit more like:

WITH querystats AS
(	SELECT	OBJECT_NAME(qt.objectid) AS ProcedureName,	SUM(qs.execution_count) OVER (PARTITION BY OBJECT_NAME(qt.objectid)) AS ExecutionCount,	qs.creation_time AS CreationTime,	ROW_NUMBER() OVER (PARTITION BY OBJECT_NAME(qt.objectid) ORDER BY creation_time DESC) AS rownum	FROM sys.dm_exec_query_stats AS qs	CROSS APPLY sys.dm_exec_sql_text(qs.[sql_handle]) AS qt	WHERE	qt.[dbid] = DB_ID()	AND OBJECT_NAME(qt.objectid) LIKE '%%'
)
SELECT	qs.ProcedureName,	qs.ExecutionCount,	qs.ExecutionCount
FROM querystats qs
WHERE	qs.rownum = 1;
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Business Logic

Ed Elliott hits a classic architectural argument—whether business logic should be in stored procedures;

Stackoverflow is a specific use case and they decided to use .Net so they have a specific set of problems to deal with in terms of performance. They deploy (as I understand it) 10 times a day so if they need to change a query then they can quickly and easily – how quickly can you modify code and get it to production to fix a problem causing downtime on your mission critical app written in powerbuilder 20 years ago? (I jest but you get the point)

I like Ed’s back-and-forth arguing, as there are legitimate cases for both sides and the best answer almost always is somewhere in between for line of business apps.   I have three points that I tend to mention whenever this discussion comes up.

First, a lot of “business logic” is actually data logic.  Check constraints, foreign key constraints, unique key constraints, and even primary key constraints (for non-surrogate primary keys) are business rules, but they’re business rules around how the data is shaped and it’s a lot better to use your database system to maintain those rules.

Second, validation rules should be everywhere.  The fancy Javascript library should do validation, the server-side business logic should do validation, and the database should do validation.  You don’t know what’s going to skip one or more of these layers, and your database is the final gatekeeper preventing bad data from sneaking into your system.

Third, at the margin, go where your maintenance developers are most comfortable.  If they’re really good with C# but not good with SQL, the marginal business logic (the stuff you could really go either way on) should stay in the app tier; if your maintainers have really strong SQL skills but are lagging on the .NET side, I’d stick the marginal logic in stored procedures.

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Finding Nested Stored Procedures

Michael J. Swart has a script to find nested stored procedures:

Adventureworks seems just fine to me. Only four instances of procedures calling procedures. I looked at the database I work with most. Hundreds of procedures (representing 15% of the procedures) call other procedures. On the other end of the spectrum is Stackoverflow. I understand that they don’t use stored procedures at all.

Check out the comments for more notes.

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Permissions To Create Stored Procedures

Kenneth Fisher shows the permissions necessary to create a stored procedure:

The user still won’t be able to create procedures or views. And if you think about it in the right way it makes sense. While the CREATE permissions give us the ability to create objects what they don’t give us is a place to put them. Schemas are containers for most of the objects in databases. So in order change the schema (by putting an object in it) we need to grant ALTER on it. So for the CREATE to work we need to:

Getting the right granularity for permissions is a vital part of securing a SQL Server instance.

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External Temp Tables And Plan Cache Bloat

Sebastian Meine warns us about using external temporary tables in stored procedures:

When a stored procedure is compiled that is accessing an external temp table, SQL Server has no guarantee that the next time this stored procedure is called it is called from the same connection. However, if it is called from a different connection, the accessed temp table might contain significantly more (or less) data making a different execution plan preferable.

A simple way to deal with this situation is to force a recompilation every time a procedure that works with external temporary tables is executed. SQL Server is not going that route. Instead, SQL Server caches the procedure once for each connection. That can safe a significant amount of CPU resources when the procedure in question is called within a loop.

Try to avoid using external temp tables.  There are some cases in which it’s a very useful construct, but

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Parameterizing Procedures

Monica Rathbun shows how to combine several report queries:

I try to parameterize as many stored procedures as possible. This not only minimizes the amount of procedures I need to maintain, it in my opinion is a much cleaner way to code. It disturbs me when I see multiple stored procedures that pull the exact same data, but may have slight differences between them. Whether it be a sort, a where clause, or even just an extra field or two that makes it different, some developers think you need a different procedure for each one . Why not consolidate and parameterize?

The next step might be using dynamic SQL to build a query if there’s as much overlap as we see in Monica’s example.

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