[jira] [Commented] (DERBY-5466) Add support for SQL Standard statistics functions, such as STDDEV_POP, STDDEV_SAMP, VAR_POP, VAR_SAMP

["Rick Hillegas (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-5466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14654248#comment-14654248 ] 

Rick Hillegas commented on DERBY-5466:
--------------------------------------

Thanks, Scott. You will eliminate the out-of-memory possibility (and the 2-pass nature of the Sybase approach) if you make the following additional changes:

1) Replace the ArrayList field with a Sums field.

2) Eliminate the computeSums() method, moving the += lines into accumulate().

A class header comment showing the IBM formula you are using would be nice too.

Thanks!
-Rick

> Add support for SQL Standard statistics functions, such as STDDEV_POP, STDDEV_SAMP, VAR_POP, VAR_SAMP
> -----------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-5466
>                 URL: https://issues.apache.org/jira/browse/DERBY-5466
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.8.1.2
>            Reporter: Lukas Eder
>            Priority: Minor
>              Labels: derby_triage10_10
>         Attachments: DERBY-5466.stats.2.patch, var_pop_formulas.txt
>
>
> Any of these RDBMS support the SQL standard statistics functions STDDEV_POP, STDDEV_SAMP, VAR_POP, VAR_SAMP:
> - DB2 (only STDDEV, VARIANE)
> - H2 
> - HSQLDB 
> - Ingres 
> - MySQL 
> - Oracle 
> - Postgres 
> - SQL Server (named STDEVP, STDEV, VARP, VAR)
> - Sybase ASE
> - Sybase SQL Anywhere
> These don't:
> - Derby
> - SQLite
> This would be a useful addition for Derby, I think.
> An even larger example list of possible statistics aggregate functions is listed in the Postgres documentation:
> http://www.postgresql.org/docs/9.0/static/functions-aggregate.html#FUNCTIONS-AGGREGATE-STATISTICS-TABLE



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