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https://issues.apache.org/jira/browse/PHOENIX-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14572284#comment-14572284
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James Taylor commented on PHOENIX-2018:
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bq. What's more, I add one abstract class, JavaMathOneArgumentFunction, as base
class for all one-argument math build-in function.
That's a good idea - that'll make it easier to implement the bulk of these.
bq. SqrtFunction is OrderPreserving.YES, so its result should be the same as
input.
That's why I specialize the getSortOrder() method and coerce the result of
Math.sqrt here.
You don't need to preserve the sort order if OrderPreserving is YES. Phoenix
will still do the optimization using a reverse scan if the sort order is
different. There's really no advantage to maintaining the sort order. We only
do this if we can do it in-place without allocating more memory for the
transformation (for example, with lpad and rpad).
> Implement math build-in function SQRT
> -------------------------------------
>
> Key: PHOENIX-2018
> URL: https://issues.apache.org/jira/browse/PHOENIX-2018
> Project: Phoenix
> Issue Type: Sub-task
> Reporter: Shuxiong Ye
> Assignee: Shuxiong Ye
> Fix For: 5.0.0, 4.5.0, 4.4.1
>
> Attachments:
> 0001-PHOENIX-2018-Implement-math-build-in-function-SQRT_v3.patch,
> 0001-PHOENIX-2018-Implement-math-build-in-function-SQRT_v4.patch
>
>
> # SQRT means square root.
> # Return type will be PDouble
> # OrderPreserving
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