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E-format float update performance Expand / Collapse
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Posted Sunday, July 25, 2010 8:31 AM
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Hi Everyone

I have been assigned the fun job of trying to squeeze as much performance out of our "Save(s)" and have observed an interesting phenomenon. The basic gist is that we do about 80K updates to this one table that has a key followed by 105 'nullable float' columns (note I can't change the schema)...

The observation I have made has to do with the number format one supplies the server is essentially summarized below:

Method 1. update TBL set c_W200901 = 0.000000e+00, ... where key="..."
Method 2. update TBL set c_W200901 = 0.0, ... where key="..."

Now:

Method 1: yields me a total time of 266 seconds
Method 2: yields me a total time of [color=#FF0000]536[/color] seconds

This is on a Acer laptop (select @@VERSION = Microsoft SQL Server 2008 (SP1) - 10.0.2531.0 (Intel X86) Mar 29 2009 10:27:29 Copyright (c) 1988-2008 Microsoft Corporation Enterprise Edition on Windows NT 6.0 <X86> (Build 6002: Service Pack 2) )

Has anybody experienced this before? If not and you are having slow updates with float numbers...please consider above findings. Very strange indeed!

Thanks
Post #958479
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