E-format float update performance

• marinehero

  Grasshopper

  Points: 19

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  July 25, 2010 at 8:31 am

  #221647

  [font="Tahoma"]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 536 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[/font]