Обсуждение: [pgsql-advocacy] Correlated columns & firsts
Folks, I had the impression that our new multicolumn stats feature was a first in the industry. However, a PDXPUG member said that SQL Server has something like it for the last couple versions. Anyone know if it's the same thing or not? -- Josh Berkus Containers & Databases Oh My!
On Wed, Jul 26, 2017 at 10:32 AM, Josh Berkus <josh@berkus.org> wrote: > I had the impression that our new multicolumn stats feature was a first > in the industry. However, a PDXPUG member said that SQL Server has > something like it for the last couple versions. So does Oracle. > Anyone know if it's the same thing or not? I'm pretty sure that it is. -- Peter Geoghegan
Josh Berkus wrote: > Folks, > > I had the impression that our new multicolumn stats feature was a first > in the industry. However, a PDXPUG member said that SQL Server has > something like it for the last couple versions. > > Anyone know if it's the same thing or not? A quick search led me to https://dba.stackexchange.com/questions/84747/statistics-are-multicolumn-histograms-possible which contains a pointer to https://blogs.msdn.microsoft.com/ianjo/2005/11/10/create-multi-column-statistics/ then you can see the MS docs at https://docs.microsoft.com/en-us/sql/t-sql/statements/create-statistics-transact-sql https://docs.microsoft.com/en-us/sql/relational-databases/statistics/statistics From what I can tell, they only store the correlation between the columns, so it's simpler than what we do. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>A quick search led me to
>https://dba.stackexchange.com/questions/84747/statistics-are-multicolumn-histograms-possible
>which contains a pointer to
>https://blogs.msdn.microsoft.com/ianjo/2005/11/10/create-multi-column-statistics/
>
>then you can see the MS docs at
>https://docs.microsoft.com/en-us/sql/t-sql/statements/create-statistics-transact-sql
>https://docs.microsoft.com/en-us/sql/relational-databases/statistics/statistics
>https://dba.stackexchange.com/questions/84747/statistics-are-multicolumn-histograms-possible
>which contains a pointer to
>https://blogs.msdn.microsoft.com/ianjo/2005/11/10/create-multi-column-statistics/
>
>then you can see the MS docs at
>https://docs.microsoft.com/en-us/sql/t-sql/statements/create-statistics-transact-sql
>https://docs.microsoft.com/en-us/sql/relational-databases/statistics/statistics
For Oracle:
https://blogs.oracle.com/optimizer/extended-statistics