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https://issues.apache.org/jira/browse/DRILL-202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13805925#comment-13805925
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Tommy Guy commented on DRILL-202:
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Hey guys, new here. Hope you don't mind the patch!
The ticket description describes more than just the average and std. dev.
functions mentioned in the title. I started with min b/c it and max are
easiest. If you prefer, I can split these out into sub-tickets.
My plan is to
1) Get a quick "right direction" check from someone with a little more
experience
2) Implement max and DRY out sum/max/min
3) Start on avg, std dev, ect.
> Implement average and standard deviation functions
> --------------------------------------------------
>
> Key: DRILL-202
> URL: https://issues.apache.org/jira/browse/DRILL-202
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: M2, Beta
> Reporter: Ted Dunning
> Labels: newbie
>
> I need several statistical functions including average. To be complete, I
> would like to implement several of the statistical functions from Postgres:
> {code}
> Function Argument Type Return Type Description
> avg(expression) smallint, int, bigint, real, double precision, numeric,
> or interval numeric for any integer-type argument, double precision for a
> floating-point argument, otherwise the same as the argument data type the
> average (arithmetic mean) of all input values
> max(expression) any array, numeric, string, or date/time type same as
> argument type maximum value of expression across all input values
> min(expression) any array, numeric, string, or date/time type same as
> argument type minimum value of expression across all input values
> stddev(expression) smallint, int, bigint, real, double precision, or
> numeric double precision for floating-point arguments, otherwise
> numeric historical alias for stddev_samp
> stddev_pop(expression) smallint, int, bigint, real, double precision,
> or numeric double precision for floating-point arguments, otherwise
> numeric population standard deviation of the input values
> stddev_samp(expression) smallint, int, bigint, real, double precision,
> or numeric double precision for floating-point arguments, otherwise
> numeric sample standard deviation of the input values
> variance(expression) smallint, int, bigint, real, double precision, or
> numeric double precision for floating-point arguments, otherwise
> numeric historical alias for var_samp
> var_pop(expression) smallint, int, bigint, real, double precision, or
> numeric double precision for floating-point arguments, otherwise
> numeric population variance of the input values (square of the
> population standard deviation)
> var_samp(expression) smallint, int, bigint, real, double precision, or
> numeric double precision for floating-point arguments, otherwise
> numeric sample variance of the input values (square of the sample
> standard deviation)
> {code}
> I plan to put these in with sum.
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