Making Text Search Faster

Rob Farley looks at binary collations and specifically hash functions on aggregation:

If there’s an index on the column you’re grouping, then changing the collation is going to hurt a bit. Grouping could take advantage of a Stream Aggregate under our indexed collation, but changing the column is like throwing it away the index order (ORDER BY doesn’t get handled well by changing the collation) means a Hash is required. But comparing two query plans that both use Hash Match (Aggregate), one on a case-insensitive collation and one on a binary collation, then I found the latter was slightly faster. Not as drastic a change as searching, but still 10-30% better. One would run in about 12 seconds, and one in about 10.

Be sure to check out his comments for more details.

Fix SQLPS

Chrissy LeMaire wants Microsoft to fix three things with SQLPS:

SQLPS has a lot of of bugs that need to be addressed (I’ll get to that soon), but I propose we start with these three.

  1. SQLPS module is slow to load
  2. Loading SQLPS module changes current directory to PS SQLSERVER:\>
  3. SQLPS module uses unapproved PowerShell verbs

Each item even has suggested fixes. The fixes are pretty straightforward (said the DBA who doesn’t do QA). Bugs 1 and 2 suggest modifying a few lines in SqlPsPostScript.ps1, while number 3 probably requires a recompile and we’re not really sure how challenging that will be.

Please upvote the Connect items if you use SQLPS…or don’t but would if it worked better.

Granting Permissions In AGs Or On Mirrors

Matan Yungman discusses how to grant permissions only to the replica database in a mirroring or Availability Groups scenario:

You work with Database Mirroring or AlwaysOn AG, and you want to make sure your end users work only on the secondary server. How should you do that?

This solution feels a little hacky to me.  There’s enough value in it that I could see companies doing this, but it’d be nice if there were an easier way.

DBCC UPDATEUSAGE

Slava Murygin has some information on the DBCC UPDATEUSAGE command:

As you can see, UPDATEUSAGE found three problems with that table, while was running in “ESTIMATEONLY” mode. When it run in “Fix” mode it also found and fixed only three problems. The number of rows was still left unfixed.

I think it’s fair to say that this is a relatively uncommonly-used DBCC command, but can definitely be useful in a subset of circumstances.

Plan Explorer Math

Aaron Bertrand walks through display differences between SQL Sentry Plan Explorer and SSMS:

Now, in the process of developing Plan Explorer, we have discovered several cases where ShowPlan doesn’t quite get its math correct. The most obvious example is percentages adding up to over 100%; we get this right in cases where SSMS is ridiculously off (I see this less often today than I used to, but it still happens).

Interpreting execution plans is not a trivial exercise, and this is an interesting look at how SQL Sentry developers (and supporters within the broader community) have worked on it through the years.

Don’t Use Write-Host

Steve Jones warns us away from Write-Host in Powershell:

I’ve written a few scripts and programs lately, mostly just for fun. In those scripts, I’ve used Write-Host to return output. To me, it’s been like “Print” in various languages where I can get output of a program. Often I’ll use a method/function to get info and then use print to output that to the caller.

However a few people noted that in my last script, Write-host wasn’t necessary. When I asked why, both Mike Fal and Drew Furgiule responded.

Mike and Drew are smart cookies.  Write-Host has some major limitations which hinder developers’ abilities to modularize and package viable code.

Columnstore On Temp Objects

Niko Neugebauer looks at creating columnstore indexes on temporary objects to see which ones are allowed and what limitations exist:

There is a very usable support for Columnstore Indexes within the temporary objects, but they are not appearing in any of the DMV’s to be analysed or optimised. This is especially sad in the relation to the global temporary tables which are some of the more useful temporary objects.

For the most part, I’d consider these reasonable results.  Hopefully we can get columnstore stats on temp tables, but even that’s not a huge loss.

Backups To URL Containers

Rob Sewell notes that Azure blob storage container names are case-sensitive:

If you use SQL Backup to URL to backup your databases to Azure blob storage remember that for the container name case is important

Despite all of my Linux love and C-based language tolerance, case sensitivity for filenames and development languages is a relic of a barbaric past.  Nevertheless, that’s the minefield we must traverse.

Native Spatial In SQL Server 2016

The CSS SQL Server Engineers team points out that spatial types will be a lot faster in the upcoming version of SQL Server:

The SQL Server development team was able to remove the PInvoke and PUnInvoke activities during T-SQL execution for many of the spatial methods.   A critical aspect of the change is that the change is fully compatible across the server and client scenarios. 

The same source code is used to build the managed C++ implementation and the unmanaged C++ implementation.   At the risk of understating this work the C++  managed code can be compiled with the C++ /CLI compiler, creating the managed assembly and a few, cleaver templates and macros bridge the native variations allowing C++ native compilation.  Any change to the code is made in one source file and built in two different ways.

They also have a couple of demos and point out that if you’re using a spatial index appropriately, the performance benefit from switching to 2016 is upwards of 3x.  A 3x performance improvement with no code changes is nothing to sneeze at.

New-TimeSpan

Richie Lee shows off Get-TimeSpan and New-TimeSpan:

As is the case with most things, when I find a way for getting something done in a script that is “good enough”, I’ll tend to stick with that method until that method no longer becomes fit for purpose. One such method is printing out the time that something took in PowerShell: many of the scripts on my site use this method to get the duration of a task, and I’ve been using this since PowerShell 1.0

This is certainly an improvement over the old version.

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