Guys,
Select count(*) from TAB
or
Select count( ID ) from TAB -- (assuming ID is an indexed column)
Which one is better in terms of performance? Is there any difference at all?
Thanks!
Edited:Maybe I should have posted this to the "managed" newsgroup. If any admins think that would be better, then let me know. I don't want to duplicate unnecessarily.
Hi,
We developed a custom Control Flow task for SSIS (2005, not yet had a lot of time to look at 2008 yet) and found that it does not handle versioning, or an uninstall and the resulting lack of an addressable component very gracefully.
Here is a typical scenario:
Baseline
Install component MyCustomTask 1.0
Create Project
Save Project
Action 1
Uninstall MyCustomTask 1.0 and don't install the new version (a typical user scenario!)
Open Project
SSIS acts like the world has ended, especially if the user forgot to manually remove the item from the toolbox
Fix:None, obviously, but it would be nice to be a bit more graceful and informative.
Backdoor Toolbox fix: "Cleanse" the toolbox when it goes haywire by deleting the toolbox.tbd, in Documents and Settings<UserName>Local SettingsApplication DataMicrosoftVisualStudio8.0
Action 2
Uninstall MyCustomTask 1.0 cleanly, plus removing the toolbox item by hand.
Install MyCustomTask 1.1, with identical interfaces etc, and add the toolbox item by hand.
SSIS acts like the world has ended, and fails to ask you a sensible question like "do you want to upgrade the project to use the new version of the component"
Fix:Identify major and minor version component changes and throw the user a rope.
Backdoor Fix: Go into the DTSX manually - attack the DTSExecutable ExecutableType and DTS Name, for a Task in our case and replace it with the new version info. Even if the interface for the component has changed slightly, it seems to deal with that OK.
Given the fact that it seems to be very likely that there will need to be SSIS version specific builds of components (I am assuming that a task created in 2005 will not work with 2008), what is the best way to deal with the current lack of SSIS smarts.
Would this be the best approach:
Version the interfaces, but never the builds within a version i.e. My.CustomTask90 v1.0, My.CustomTask100 v1.0 etc.
This is a bit of a pain, rather than the simpler My.CustomTask v9.0 / v10.0 etc.
Or, are there some nice improvements in the pipe to alleviate this, plus perhaps even a way to programatically add components to the toolbox, rather than the low-rent method of getting the user to do it by hand.
All suggestions gratefully received.
Thanks in advance
Gareth
from cl.exe I get a bunch of linker errors:
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