Thursday, January 31, 2008

Care required passing arrays to .Net methods in Powershell

In Powershell, argument lists for .Net methods are treated as arrays:
...which can be confusing if you want to pass an array as a single argument:

New-Object : Cannot find an overload for "MyMethod" and the argument count: ""
Instead, force the array-argument to be contained within a single-member array:
# Note the extra comma below
Makes sense when you think about it, but definitely a gotcha.

[In my case, I was caught out with the byte[] overload constructor for a MemoryStream]

Wednesday, January 30, 2008

Blobs out with SQL 2008

Recently I re-visited the blobs in/blobs out argument with a colleague. You know the one, one of you says blobs shouldn't be stored in database (principally because the last time he tried it 'blobs in' in VB 6 access to the blob data was a pain in the arse), then the other one says no they should be in the database (because the last time they tried it 'blobs out' all the files got mixed up / out of sync / weren't backed up). Etc...

Anyway, not only has Paul Randal posted a good summary of the pros and cons, but he did so as an intro to a new SQL 2008 data type 'FileStream' that attempts to bridge the two approaches (the 'have your cake and eat it' approach).

I'm cautious. Transactions at the filesystem level are a real mess (as some of the OneNote blogs make clear, especially with non-MS implementations of SMB like SAMBA). Your database backup is presumably still huge and unwieldy (or missing the blob data, which is worse?).

The main advantage of this approach seems to be that SQL can access the blob data faster through NTFS than via it's own internal MDF formats. But you've apparently still got to go via SQL to get the data, you can't (for example) just serve up images-stored-as-blobs directly via IIS. Or maybe I've missed something. Either way, the upside all seems to be focused on blob streaming performance, which may or may not be the most relevant factor for your app.

So it's possible that next year's arguments will be blobs in vs blobs out vs filestream, and still no one-size-fits all. Ah well.

Thursday, January 03, 2008

Path already mapped in workspace error with CCNet and TFS

Had a problem with CCNet that kept me here till midnight where try as I might, I just couldn't get a build to not fail with the dreaded "Path ... is already mapped in workspace ..." error:
Microsoft.TeamFoundation.VersionControl.Client.MappingConflictException: The path C:\Builds\etc\Working is already mapped in workspace someworkspace
We use a different workspace for every CCNet project to avoid collissions, and to maintain uniqueness we keep the workspace name the same as the CCNet project name. I couldn't find the workspace in question, and was pretty sure I'd already deleted it. In fact I'd used TF Sidekicks to delete all the build user's workspaces, and it still didn't work. So what was up?

Fortunately in a post 'How to handle "The path X is already mapped in workspace Y"' I learnt of the mappings cache file on the client PC, in the user's Local Settings\Application Data\Microsoft\Team Foundation\1.0\Cache\VersionControl.config file. Just nuking workspaces on the server isn't enough!

So to be sure I blew away the build server's local profile entirely, and that finally fixed it.

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