Stairway to SQL Server Indexes: Step 4, Pages and Extents

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Stairway to SQL Server Indexes: Step 4, Pages and Extents

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David Durant

Posted Monday, February 14, 2011 10:37 AM

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Comments posted to this topic are about the item Stairway to SQL Server Indexes: Step 4, Pages and Extents

Post #1063681

Brent Ozar

Posted Thursday, February 17, 2011 7:12 AM

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Nice article! Just one tweak:

"If one page in an extent is owned by TableA or IndexB, all eight pages will be owned by that same object. An exception is made for very small tables and indexes, ones that would not fill and entire extent."

Close, but not exactly. The first page of a newly created table is put into a mixed extent. When we first create a table, we don't know whether it's going to be a "very small table" - every table starts out very small. After the table has 8 pages, then future allocations are put into uniform extents, but the original pages aren't moved to uniform extents automatically. You can move them yourself by rebuilding the clustered index, though.

You can read more about it here: [url=http://msdn.microsoft.com/en-us/library/ms190969%28v=sql.90%29.aspx][/url]

Also, just to nit-pick, heh - there's a typo. It should say "would not fill AN entire extent."

Post #1065641

David Durant

Posted Tuesday, May 24, 2011 12:25 PM

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Brent,

Sorry for the long delay in replying; have been completing the remaining levels.

Will reread the level and reword it, to add your point and fix the typo.

Re the typo: Sharp eyes. Three people (self, Kalen, and Redgate) plus Word missed it.

Thanks for the input,
Dave Durant.
Author.

Post #1114311

Brent Ozar

Posted Tuesday, May 24, 2011 12:28 PM

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Glad I could help - and again, great series! The community really needed this step-by-step level of training, and I love seeing 'em go live.

Post #1114314

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