30Mar 2015 by Grant Fritchey No Comments

Does the New Cardinality Estimator Reduce Bad Parameter Sniffing

T-SQL
No. Next question. Although, that answer can be slightly, ever so slightly, nuanced... Parameter sniffing is a good thing. But, like a good wine, parameter sniffing can go bad. It always comes down to your statistics. A very accurate set of statistics with very little data skew (some values that have radically more/less data than other values) and a very even distribution (most values have approximately similar cardinality), and parameter sniffing is your bestest buddy on the planet (next to a tested backup). But, introduce some data skew, let the stats get wildly out of date, or suffer from seriously uneven distribution, and suddenly your best friend is doing unspeakable things to your performance (kind of like multi-statement table valued user defined functions). SQL Server 2014 has the first upgrade…
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02Jul 2014 by Grant Fritchey 5 Comments

Statistics and Natively Compiled Procedures

T-SQL
Statistics are one of the single most important driving factors for the behavior of the query optimizer. The cardinality estimates stored within the statistics drive costing and costing drives the decision making of the optimizer. So, how does this work with the new SQL Server 2014 natively compiled procedures? Differently. In-memory tables do not maintain their statistics automatically. Further, you can't run DBCC SHOW_STATISTICS to get information about those statistics, so you can't tell if they're out of date or not or what the distribution of the data is within them. So, if I create some memory optimized tables, skip loading any data into them and then run this standard query: SELECT a.AddressLine1, a.City, a.PostalCode, sp.Name AS StateProvinceName, cr.Name AS CountryName FROM dbo.Address AS a JOIN dbo.StateProvince AS sp ON sp.StateProvinceID =…
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17Jun 2014 by Grant Fritchey 2 Comments

Natively Compiled Procedures and Bad Execution Plans

Uncategorized
I've been exploring how natively compiled procedures are portrayed within execution plans. There have been two previous posts on the topic, the first discussing the differences in the first operator, the second discussing the differences everywhere else. Now, I'm really interested in generating bad execution plans. But, the interesting thing, I wasn't able to, or, rather, I couldn't see evidence of plans changing based on silly things I did to my queries and data. To start with, here's a query: CREATE PROC [dbo].[AddressDetails] @City NVARCHAR(30) WITH NATIVE_COMPILATION, SCHEMABINDING, EXECUTE AS OWNER AS BEGIN ATOMIC WITH (TRANSACTION ISOLATION LEVEL = SNAPSHOT, LANGUAGE = N'us_english') SELECT a.AddressLine1, a.City, a.PostalCode, sp.Name AS StateProvinceName, cr.Name AS CountryName FROM dbo.Address AS a JOIN dbo.StateProvince AS sp ON sp.StateProvinceID = a.StateProvinceID JOIN dbo.CountryRegion AS cr ON…
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10Jun 2014 by Grant Fritchey 3 Comments

Differences In Native Compiled Procedures Execution Plans

Uncategorized
All the wonderful functionality that in-memory tables and natively compiled procedures provide in SQL Server 2014 is pretty cool. But, changes to core of the engine results in changes in things that we may have developed a level of comfort with. In my post last week I pointed out that you can't see an actual execution plan for natively compiled procedures. There are more changes than just the type of execution plan available. There are also changes to the information available within the plans themselves. For example, I have a couple of stored procedures, one running in AdventureWorks2012 and one in an in-memory enabled database with a few copies of AdventureWorks tables: --natively compiled CREATE PROC dbo.AddressDetails @City NVARCHAR(30) WITH NATIVE_COMPILATION, SCHEMABINDING, EXECUTE AS OWNER AS BEGIN ATOMIC WITH (TRANSACTION ISOLATION LEVEL…
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05Jun 2014 by Grant Fritchey 2 Comments

Natively Compiled Procedures and Execution Plans

T-SQL
The combination of in-memory tables and natively compiled procedures in SQL Server 2014 makes for some seriously screaming fast performance. Add in all the cool functionality around optimistic locking, hash indexes and all the rest, and we're talking about a fundamental shift in behavior. But... Ah, you knew that was coming. But, you can still write bad T-SQL or your statistics can get out of date or you can choose the wrong index, or any of the other standard problems that come up that can negatively impact all those lovely performance enhancements. Then what? Well, same as before, take a look at the execution plan to understand how the optimizer has resolved your queries. But... Yeah, another one. But, things are a little different with the natively compiled procedures and…
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01Apr 2014 by Grant Fritchey 15 Comments

SQL Server 2014 New Defaults

T-SQL
Today, April 1st, 2014, marks the release of SQL Server 2014. There are tons and tons of great new methods and functions and processes within the product. We're all going to be learning about them for quite a while to come. One of the most exciting though is one of the changes to the defaults. In the past there's been a lot of debate around how best to configure your databases. What cost threshold should be set for parallelism, the max degree of parallelism, memory settings, auto growth, and all sorts of other settings affect how your databases work. But, Microsoft has finally done something smart. They've bowed to the pressure of hundreds and hundreds of DBAs, Database Developers and Developers around the world. They've finally done the one thing…
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12Feb 2014 by Grant Fritchey 1 Comment

SQL Server 2014 and the New Cardinality Estimator

Uncategorized
Cardinality, basically the number of rows being processed by an operation with the optimizer, is a calculation predicated on the statistics available for the columns in question. The statistics used are generally either the values from the histogram or the density. Prior to SQL Server 2014, and going all the way back to SQL Server 7.0 (in the Dark Ages when we had to walk uphill to our cubicles through 15 feet of snow battling Oracle DBAs and Fenris the whole way), there's been one cardinality estimator (although you can modify the behavior somewhat with a traceflag in 2008R2 and 2012). Not any more. There's a possibility for really complex, edge-case queries, that you may run into a regression from this. You control whether or not you get the new…
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19Dec 2013 by Grant Fritchey 2 Comments

How to Set Up Managed Backups in SQL Server 2014

Azure
Earlier this week I introduced the concept of Managed Backups (and caused less of a turmoil than I thought I would). Now I want to show you how it works. It's really simple and quite well documented. Before you get to the, insanely simple, task of actually enabling Managed Backup, you will need to go through the prerequisites. First, and this should be obvious, but I'll state it, just in case, you need to set up an Azure storage account. That's so insanely straight forward that I'm not going to say more. Then, you have to set up encryption on your system. I used these commands to prep it: CREATE MASTER KEY ENCRYPTION BY PASSWORD = '$qlserver2012queryperformancetuning'; CREATE CERTIFICATE CloudDojoCert WITH SUBJECT = 'Backup Encryption Certificate'; Again, shouldn't have to…
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17Dec 2013 by Grant Fritchey 3 Comments

Introducing Managed Backups in SQL Server 2014

Azure
Some of the new functionality of 2014 is straight forward, non-controversial and easily welcomed by the community. Think, updateable column store indexes. Some of the new functionality is going to raise an eyebrow or three (most of the time, not on one person, but you know the #sqlfamily, we have some interesting mutations represented). Think... managed backups. Now, why on earth would a process that takes backups for you, including log backups, does it automatically per a schedule and/or when data has changed sufficiently, stores it offsite for protection and is easy to set up and maintain going to cause so much controversy? Hey, I'm wrong, it won't, move along... Or, maybe, I'm right, and this is going to raise more than eyebrows. We're talking about surrendering control over your…
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11Dec 2013 by Grant Fritchey 4 Comments

SQL Server 2014 Backup to URL

Azure, T-SQL
I'm absolutely in love with the concept of being able to create a backup directly to a protected, off-site location. Yeah, you can spend all sorts of money on terribly wonderful technology to enable that within your enterprise. And if you have that kind of money, great. But, what if you're like most everyone else and you just want a little more protection without mortgaging the house? Let's take a look at one possibility, backup to URL. There have been ways to backup to hosted storage, whether it was DropBox, AWS or Azure blob storage, for quite a while. But, every method I tried out involved setting up some type of drive on your system. As soon as you had your K:\ drive mapped out to AWS or whatever, you…
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