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https://issues.apache.org/jira/browse/CALCITE-2339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16511707#comment-16511707
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James Duong commented on CALCITE-2339:
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* missing MINUTE from the switch
* >>> done
* I don't think the visitor can throw FoundOne
* >>> the DateTimePlusToTsAddVisitor can throw a FoundOne() by design - if it
runs into a multi-field interval since we can't transform that to timestampAdd
([https://github.com/jduo/calcite/blob/16e9e46c0db8e46a5e14beed208ca486f24bf09a/core/src/main/java/org/apache/calcite/rex/RexUtil.java#L2711|https://github.com/jduo/calcite/blob/16e9e46c0db8e46a5e14beed208ca486f24bf09a/core/src/main/java/org/apache/calcite/rex/RexUtil.java#L2711)]
)
* only call the method if the condition is not null, do not check for nulls in
the method, and assume the method returns not-null
* >>> assuming this is in reference to the convertDatetimePlusToTimestampAdd()
method. I would like to have the semantics to return either the transformation
is not possible, or the completed transformation. Would a Java8 optional be
more appropriate?
* indentation is off in a couple of places
* >>> I'll check this out.
* need some unit tests
* >>> Will do.
* rather than trying to do constant reduction to convert interval to integer,
could you just use "cast(<interval expression> AS INTEGER)"? less code to
maintain
* >>> I thought about this, but realized that if we ever need to invoke this
transformation to timestampadd, it means the backend probably doesn't support
intervals so you can't use CAST(<interval expression>). What might work is to
create the Cast node, then use RexSimplify to see if it can be constant-reduced
to just an integer literal. I'll look into this.
> JDBC adapter should transform timestamp arithmetic for target database
> -----------------------------------------------------------------------
>
> Key: CALCITE-2339
> URL: https://issues.apache.org/jira/browse/CALCITE-2339
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Priority: Major
> Attachments: Datetime Addition - Calcite.pdf
>
>
> JDBC adapter should transform timestamp arithmetic for target database.
> There are two ways in Calcite to add intervals to timestamps: the
> TIMESTAMP_ADD function and the "<timestamp> + <interval>" operator.
> The attached document (authored by James Doung) describes their pros and cons.
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