March 3, 2018

Can a single query deadlock itself? Apparently, yes: A curious case of Intra-query Parallelism

By Emanuele Meazzo

3 Min read

1 comment

03March

Imagine that you’re in a SQL data warehouse in the middle of the night, a single stored procedure is running, is nothing else, and it’s simply doing inserts and updates, one statement at the time, but then.. Deadlock. How can it be? Something else must be running, right? Someone launched something else, or a transaction was left open the day before, or the Russians were spying...

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February 26, 2018

Scan Performance Showdown: INROW Predicate pushdown VS Batch Mode Adaptive Join vs Columnstore indexes

By Emanuele Meazzo

6 Min read

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26February

I was reading Paul White’s post about bitmaps in SQL Server and, other than realizing that I basically know nothing about anything (like a Socrate’s epiphany) I wanted to at least see how this good stuff added up in the latest 7 years. Down with experimenting, we’re doing this LIVE! (Well, it’s live for me, for you it’s still a blog post) I’ll start by creating...

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February 18, 2018

Creating a Perfmon and Filestats reports in PowerBI [Part 1]

By Emanuele Meazzo

5 Min read

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18February

If you work for a big company, you may have a bunch of instances/databases under your control, you ran whatever monitoring tool has been provided and everybody is happy; But if your’re like me and you’re working for a big number of customers, each one with a different version of SQL and own configuration/security policies, with no monitoring tool directly available, and have to answer...

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February 17, 2018

How to get and decode callstacks in in extended events for recent versions of SQL Server

By Emanuele Meazzo

4 Min read

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17February

The other day I was reading about spinlocks and troubleshooting and it mentioned to get the callstack for a certain xevent and to decode it using the windows debugging symbols, however, that material was related to SQL Server 2012 and the steps weren’t basically replicabile for a modern version like SQL 2016/2017 (or even 2014 I think, but haven’tn checked personally), I searched...

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February 12, 2018

Create an asynchronous multithreaded workflow on your SQL Server using the Service Broker

By Emanuele Meazzo

12 Min read

2 comments

12February

As any other *Server, SQL Server is born with concurrency in mind, a lot of users/applications can connect concurrently and do their job, as designed, perfect, but, what if you’re the only user? What if you’re in some kind of data warehouse configuration where you have to ETL, or you are in a maintenance window and have to do a bunch of stuff in that time, or simply you need to launch...

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February 3, 2018

THREADPOOL, or, Why is SQL server not responsive even the CPU is basically idle?

By Emanuele Meazzo

3 Min read

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03February

It’s a late Friday afternoon, this means that somebody is going to tell you that the server is unresponsive, users are blocked and there is a imperative deadline for the business at 6PM (which you think is probably because they don’t want to be late to the happy hour), so you do what you do best: sigh and log on to see what’s going on with this instance. You fire up SSMS, and...

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February 1, 2018

How to avoid the traps when dealing with parallelism

By Emanuele Meazzo

4 Min read

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01February

I work with a vendor application which needs to do all sorts of data crunching in some nightly batches, and, depending on the size of data, this process may take a lot of time. Some time a go a colleague said: “we need more parallelism, we want to parallelize all the things! What can you think may go wrong?” This opened a stream of consciousness that could be really handled only by...

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