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https://issues.apache.org/jira/browse/CALCITE-3531?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17012135#comment-17012135
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Julian Hyde commented on CALCITE-3531:
--------------------------------------
I do see the need for a function in Flink that returns the current wallclock
time. We could introduce a new function {{WALLCLOCK_TIMESTAMP}}.
Perhaps in Flink continuous queries, if people write {{CURRENT_TIMESTAMP}}
Flink will convert it to {{WALLCLOCK_TIMESTAMP}}. That way, people get to use
the function that they are familiar with, but we keep the valuable optimization
properties of {{CURRENT_TIMESTAMP}}.
When we specify {{WALLCLOCK_TIMESTAMP}}, we should probably make it
[monotonic|https://metacpan.org/pod/Time::Monotonic]. We don't want it jumping
backwards if there is an NTP update or a leap second.
There could also be {{WALLCLOCK_DATE}}, {{WALLCLOCK_TIME}},
{{LOCAL_WALLCLOCK_TIMESTAMP}}, etc.
> 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
> Assignee: Danny Chen
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.22.0
>
> Time Spent: 2.5h
> 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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