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Query Optimizer

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SQL Saturday #35 Dallas
published 112 days, 12 hours, 57 minutes ago posted by sasa 121 days, 14 hours, 34 minutes ago
Saturday, April 10, 2010 7:01:15 AM GMT Thursday, April 01, 2010 5:25:01 AM GMT
SQL Saturday #35 Dallas
SQL Saturday is coming to Dallas. May 22nd so add it to your calendar and register. SQLSaturday is a free day-long training event for SQL Server professionals and those wanting to learn about SQL Server. This event will be held on May 22, 2010 at the Region 10 Education Service Center, 400 E Spring Valley [...] (more)
category: News | clicked: 0 | comment | | source: jasonmassie.com
tags: Mixed Workloads, Query Optimizer, Query Tuning, sql pass, SQL Server, SQLSaturday, TSQL
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Sampling Problem with Filtered Statistics
published 158 days, 15 hours, 13 minutes ago posted by sasa 168 days, 9 hours, 34 minutes ago
Tuesday, February 23, 2010 4:45:21 AM GMT Saturday, February 13, 2010 10:24:53 AM GMT
Sampling Problem with Filtered Statistics
I was writing a blog post to show how to solve the problem of bad estimations due to uneven data distribution with filtered statistics. After an hour or so of banging my head against the wall, I discovered that I ran into a bug feature. It appears that if the predicate on the filtered stats [...] (more)
category: News | clicked: 0 | comment | | source: jasonmassie.com
tags: bugfix, filtered indexes, Query Optimizer, SQL Server, statistics
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Filtered Stats to Counter Data Skew Issues
published 162 days, 15 hours, 29 minutes ago posted by sasa 168 days, 18 hours, 3 minutes ago
Friday, February 19, 2010 4:29:33 AM GMT Saturday, February 13, 2010 1:55:10 AM GMT
Filtered Stats to Counter Data Skew Issues
There are a handful of things that can make SQL Server choose a “bad plan”. They usually revolve around variable sized result sets. Some problematic scenarios are parameter sniffing, data skew, local variables, table variables, UDF’s or complex calculations in the where clause. All of these and more are detailed in my favorite and recently [...] (more)
category: News | clicked: 1 | comment | | source: jasonmassie.com
tags: Query Optimizer, Query Tuning, SQL Server, statistics, TSQL
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Filtered Stats to Counter Data Skew Issues
published 281 days, 4 hours, 16 minutes ago posted by sasa 290 days, 16 hours, 52 minutes ago
Friday, October 23, 2009 3:42:26 PM GMT Wednesday, October 14, 2009 3:06:49 AM GMT
Filtered Stats to Counter Data Skew Issues
There are a handful of things that can make SQL Server choose a “bad plan”. They usually revolve around variable sized result sets. Some problematic scenarios are parameter sniffing, data skew, local variables, table variables, UDF’s or complex calculations in the where clause. All of these and more are detailed in my favorite and recently [...] (more)
category: News | clicked: 4 | comment | | source: jasonmassie.com
tags: Query Optimizer, Query Tuning, SQL Server, statistics, TSQL
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Sampling Problem with Filtered Statistics
published 282 days, 4 hours, 21 minutes ago posted by sasa 291 days, 17 hours, 30 minutes ago
Thursday, October 22, 2009 3:37:29 PM GMT Tuesday, October 13, 2009 2:28:15 AM GMT
Sampling Problem with Filtered Statistics
I was writing a blog post to show how to solve the problem of bad estimations due to uneven data distribution with filtered statistics. After an hour or so of banging my head against the wall, I discovered that I ran into a bug feature. It appears that if the predicate on the filtered stats [...] (more)
category: News | clicked: 1 | comment | | source: jasonmassie.com
tags: bugfix, filtered indexes, Query Optimizer, SQL Server, statistics
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How the Query Optimizer Uses Statistics – Part II
published 309 days, 6 hours, 12 minutes ago posted by sasa 319 days, 4 hours, 45 minutes ago
Friday, September 25, 2009 1:46:41 PM GMT Tuesday, September 15, 2009 3:13:45 PM GMT
How the Query Optimizer Uses Statistics – Part II
I got a question from a reader of my post How the Query Optimizer Uses Statistics (http://sqlblog.com/blogs/ben_nevarez/archive/2009/09/03/how-the-query-optimizer-uses-statistics.aspx) and I thought that it would be a good idea to post my answer here. Basically the request was to expand the previous example for a predicate with two columns.   First, a reminder that the histogram only shows the values of the first column of the statistics object. So, how the Query Optimizer does this?   One way to... (more)
category: Query | clicked: 1 | comment | | source: sqlblog.com
tags: Query Optimizer, statistics
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Statistics Used by the Query Optimizer in SQL Server White Paper
published 319 days, 6 hours, 57 minutes ago posted by sasa 326 days, 4 hours, 24 minutes ago
Tuesday, September 15, 2009 1:01:15 PM GMT Tuesday, September 08, 2009 3:34:50 PM GMT
Statistics Used by the Query Optimizer in SQL Server White Paper
In case you are not aware, the excellent white paper “Statistics Used by the Query Optimizer in SQL Server” has been updated for SQL Server 2008... (more)
category: News | clicked: 2 | comment | | source: sqlblog.com
tags: Query Optimizer, statistics
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The Query Optimizer and Contradiction Detection
published 360 days, 7 hours, 28 minutes ago posted by sasa 361 days, 2 hours, 54 minutes ago
Wednesday, August 05, 2009 12:30:04 PM GMT Tuesday, August 04, 2009 5:04:22 PM GMT
The Query Optimizer and Contradiction Detection
One of the many interesting topics I found while working as technical editor of the SQL Server 2008 Internals book was the concept of contradiction detection. So, in this post I will to try to expand on this topic and provide some additional examples.   Contradiction detection is performed by SQL Server during the early steps of the query optimization process. During this process the Query Optimizer tries to find contradictions that can be removed and can make the query perform better. Since these ... (more)
category: Query | clicked: 2 | comment | | source: sqlblog.com
tags: Contradiction Detection, Query Optimizer