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Showing page 2 of 17 (166 total posts)
  • Monitoring skew in PDW

    When you have data stored across several servers, skew becomes very significant. In SQL Server Parallel Data Warehouse (PDW), part of the Analytics Platform System (APS), data is stored in one of two ways – distributed or replicated. Replicated data is copied in full across every compute node (those servers which actually store user data), while ...
    Posted to Rob Farley (Weblog) by rob_farley on May 11, 2015
  • Tuning slow spatial queries in SQL Server

    Even with the right indexes in place, spatial queries in SQL Server are often too slow – but they needn’t be. Two of the most commonly found patterns of query in the spatial world are when you’re looking for the nearest thing to where you are (which I’ve written about before), and when you’re looking for the points that are within a particular ...
    Posted to Rob Farley (Weblog) by rob_farley on April 28, 2015
  • SHOWPLAN permission denied even if the database isn’t actually used

    To view a query plan, you need SHOWPLAN permission on the database level at least. You have this if you have CONTROL DATABASE, or CONTROL SERVER, or if you have ALTER TRACE at the instance level. I know this last one because it’s mentioned in Books Online on the ‘Database Permissions’ page, not because it’s particularly intuitive. As a ...
    Posted to Rob Farley (Weblog) by rob_farley on April 14, 2015
  • Tuning Parallel Data Warehouse Queries

    Performance tuning in regular SQL Server can be addressed in a number of ways. This can involve looking at what’s going on with the disk configuration, the memory configuration, the wait stats, the parallelism settings, indexing, and so much more. But if you have a Parallel Data Warehouse (PDW) environment, then there are a lot of things that are ...
    Posted to Rob Farley (Weblog) by rob_farley on March 9, 2015
  • Why isn’t my filtered index being used?

    Quite often, people have filtered indexes but find they’re not being used as often as they’d like. I was reminded of this recently when I read a good post by Kendra Little from about filtered indexes. In it, Kendra talks about how the WHERE clause of a filtered index allows an IN clause, but not an OR clause (to quote someone from ...
    Posted to Rob Farley (Weblog) by rob_farley on February 22, 2015
  • SQL Injection – the golden rule

    The problem with SQL Injection is that most people don’t realise the fundamental concept which makes SQL Injection vulnerability not only easy to spot, but also easy to prevent. And it’s the thing that SQL Injection has in common with countless other hacking mechanisms that have been around since the early days of computing. The simple truth is ...
    Posted to Rob Farley (Weblog) by rob_farley on February 9, 2015
  • Medians pre-SQL 2012

    SQL 2012 was a big release for working out the median in SQL Server, with the advent of the function PERCENTILE_CONT(). It’s a very elegant way of working out the median (hint, that’s the 0.5 point), even though it’s not actually an aggregate function, as I’ve written before. Plus – it doesn’t even perform well. About a year ago, Aaron Bertrand ...
    Posted to Rob Farley (Weblog) by rob_farley on January 26, 2015
  • Four SQL MVPs at LobsterPot – including three in Australia

    Today LobsterPot Solutions sets a new first. We are the only company to ever employ three current Australian SQL MVPs, giving us four awardees in total. Congratulations to Martin Cairney who joins Julie Koesmarno (AUS), Ted Krueger (USA) and me (AUS) as recipients of this prestigious award. This demonstrates LobsterPot's ongoing commitment to the ...
    Posted to Rob Farley (Weblog) by rob_farley on January 1, 2015
  • Minimising Data Movement in PDW Using Query Optimisation Techniques

    This is a white paper that I put together recently about APS / PDW Query Optimisation. You may have seen it at as well, but in case you haven’t, read on! I think the significance of this paper is ...
    Posted to Rob Farley (Weblog) by rob_farley on December 4, 2014
  • SQL Spatial: Getting “nearest” calculations working properly

    If you’ve ever done spatial work with SQL Server, I hope you’ve come across the ‘nearest’ problem. You have five thousand stores around the world, and you want to identify the one that’s closest to a particular place. Maybe you want the store closest to the LobsterPot office in Adelaide, at -34.925806, 138.605073. Or our new US office, at ...
    Posted to Rob Farley (Weblog) by rob_farley on August 14, 2014
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