Adam Machanic, Boston-based SQL Server developer, shares his experiences with programming, monitoring, and performance tuning SQL Server. And the occasional battle with the query optimizer.
In the
article on handling bitmasks I posted the other day, I made
a fatal error in the splitBitmask function. The function treated the low byte as the first byte, instead of the high byte. Therefore:
0x01 != 0x0001
... and that is not good!
So here's a corrected version that fixes the problem:
CREATE FUNCTION dbo.splitBitmask
(
@Bitmask VARBINARY(4096)
)
RETURNS TABLE
AS
RETURN
(
SELECT Number
FROM BitmaskNumbers
WHERE (SUBSTRING(@Bitmask, DATALENGTH(@Bitmask) - Byte + 1, 1) & BitValue) = BitValue
AND Byte <= DATALENGTH(@Bitmask)
)
GO
More to come soon... Bit shifting, logical operators, and other fun ways to annoy this guy:
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About Adam Machanic
Adam Machanic is a Boston-based SQL Server developer, writer, and speaker. He focuses on large-scale data warehouse performance and development, and is author of the award-winning SQL Server monitoring stored procedure, sp_WhoIsActive. Adam has written for numerous web sites and magazines, including SQLblog, Simple Talk, Search SQL Server, SQL Server Professional, CoDe, and VSJ. He has also contributed to several books on SQL Server, including "SQL Server 2008 Internals" (Microsoft Press, 2009) and "Expert SQL Server 2005 Development" (Apress, 2007). Adam regularly speaks at conferences and training events on a variety of SQL Server topics. He is a Microsoft Most Valuable Professional (MVP) for SQL Server, a Microsoft Certified IT Professional (MCITP), and an alumnus of the INETA North American Speakers Bureau.