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https://issues.apache.org/jira/browse/CALCITE-3531?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16980644#comment-16980644
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Danny Chen commented on CALCITE-3531:
-------------------------------------
Thanks for the feedback [~hyuan] and [~amaliujia], i reference the standard SQL
2011-Annex C 15), and it says:
{quote}The time of evaluation of the CURRENT_DATE, CURRENT_TIME, and
CURRENT_TIMESTAMP
functions during the execution of an SQL-statement is
implementation-dependent.{quote}
So, there is no standard to say if these functions should be deterministic or
not.
Personally, i'm inclined to the MS-SQL, because for stream sql, it's
meaningless to returns a start time as CURRENT_TIMESTAMP.
For batch, such as CURRENT_DATE, we can use this function to group the dataset
by date, if it always returns the start time, we can not do that.
> AggregateProjectPullUpConstantsRule should not remove deterministic function
> group key if the function is dynamic
> -----------------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-3531
> URL: https://issues.apache.org/jira/browse/CALCITE-3531
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.21.0
> Reporter: Danny Chen
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.22.0
>
> Time Spent: 2h
> Remaining Estimate: 0h
>
> Now AggregateProjectPullUpConstantsRule simplify the query:
> {code:sql}
> select hiredate
> from sales.emp
> where sal is null and hiredate = current_timestamp
> group by sal, hiredate
> having count(*) > 3
> {code}
> from plan:
> {code:xml}
> LogicalProject(HIREDATE=[$1])
> LogicalFilter(condition=[>($2, 3)])
> LogicalAggregate(group=[{0, 1}], agg#0=[COUNT()])
> LogicalProject(SAL=[$5], HIREDATE=[$4])
> LogicalFilter(condition=[AND(IS NULL($5), =($4, CURRENT_TIMESTAMP))])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> to plan:
> {code:xml}
> LogicalProject(HIREDATE=[$1])
> LogicalFilter(condition=[>($2, 3)])
> LogicalProject(SAL=[$0], HIREDATE=[CURRENT_TIMESTAMP], $f2=[$1])
> LogicalAggregate(group=[{0}], agg#0=[COUNT()])
> LogicalProject(SAL=[$5], HIREDATE=[$4])
> LogicalFilter(condition=[AND(IS NULL($5), =($4,
> CURRENT_TIMESTAMP))])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> which is unsafe, because for stream sql, we need to group data by dateTime,
> also the result is wrong if a batch job runs across days.
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