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https://issues.apache.org/jira/browse/CALCITE-3412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16952463#comment-16952463
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Julian Hyde commented on CALCITE-3412:
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It makes sense to also implement {{DAYOFWEEK(DATE)}}. In {{SqlFunctions}}, add
a function {{int dayOfWeek(DataContext)}}.
How do we know the first day of the week? It turns out that we have a
{{TimeZone}} and a {{Locale}} in our {{DataContext}} (based on connection
properties). With these, we can do {{Calendar.getInstance(timeZone,
locale).getFirstDayOfWeek()}}.
The implementation of {{FLOOR(... TO WEEK)}} should call {{dayOfWeek(root)}}.
> Response Error for FLOOR TIMESTAMP TO WEEK
> -------------------------------------------
>
> Key: CALCITE-3412
> URL: https://issues.apache.org/jira/browse/CALCITE-3412
> Project: Calcite
> Issue Type: Bug
> Components: core
> Environment: mac,linux
> Reporter: huaicui
> Priority: Major
> Attachments: image-2019-10-15-13-33-34-896.png
>
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> Floor timestamp to week exist error:
> The start day of the week is not Sunday or Monday, calcite use Thursday to
> split a week.
> Example:
> sql: select FLOOR(CAST('2017-01-28' AS TIMESTAMP) TO WEEK);
> Response:
> 2017-01-26 00:00:00.0
>
> 2017-01-26 is Tuesday that is not our expect result. As result, 2017-01-22 is
> the first day that we expect.
>
>
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