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https://issues.apache.org/jira/browse/CALCITE-2980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17827753#comment-17827753
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Julian Hyde commented on CALCITE-2980:
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A good test is really valuable. I wouldn't disable the whole test, because
you'll never find time to re-enable it. So, I'd take the time to selectively
disable tests. Use 'if' rather than comments, to minimize changes to the .iq
file.
It's possible that it's less effort to implement a format string element than
to disable a test. If so, do that.
> Implement the FORMAT clause of the CAST operator
> ------------------------------------------------
>
> Key: CALCITE-2980
> URL: https://issues.apache.org/jira/browse/CALCITE-2980
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Jerin John
> Priority: Major
> Labels: pull-request-available
>
> SQL:2016 adds an optional {{FORMAT format}} clause to the {{CAST}} operator.
> It is a standard way to do what functions like {{TO_DATE}}, {{TO_NUMBER}},
> {{TO_CHAR}}, {{TO_TIMESTAMP}} have done in an ad hoc way (and with differing
> specifications among databases).
> Here is an example:
> {code:java}
> cast('01-05-2017' as date format 'DD-MM-YYYY')
> {code}
> The following paragraphs are copied from IMPALA-4018, which describes
> implementing this in Impala. (That case also describes cases where the
> implementations of {{TO_TIMESTAMP}} etc. in Hive, Impala, Oracle and
> PostgreSQL are not consistent with each other. We should take note as we
> implement these functions in Calcite.)
> SQL:2016 defines the following datetime templates
> {noformat}
> <datetime template> ::=
> { <datetime template part> }...
> <datetime template part> ::=
> <datetime template field>
> | <datetime template delimiter>
> <datetime template field> ::=
> <datetime template year>
> | <datetime template rounded year>
> | <datetime template month>
> | <datetime template day of month>
> | <datetime template day of year>
> | <datetime template 12-hour>
> | <datetime template 24-hour>
> | <datetime template minute>
> | <datetime template second of minute>
> | <datetime template second of day>
> | <datetime template fraction>
> | <datetime template am/pm>
> | <datetime template time zone hour>
> | <datetime template time zone minute>
> <datetime template delimiter> ::=
> <minus sign>
> | <period>
> | <solidus>
> | <comma>
> | <apostrophe>
> | <semicolon>
> | <colon>
> | <space>
> <datetime template year> ::=
> YYYY | YYY | YY | Y
> <datetime template rounded year> ::=
> RRRR | RR
> <datetime template month> ::=
> MM
> <datetime template day of month> ::=
> DD
> <datetime template day of year> ::=
> DDD
> <datetime template 12-hour> ::=
> HH | HH12
> <datetime template 24-hour> ::=
> HH24
> <datetime template minute> ::=
> MI
> <datetime template second of minute> ::=
> SS
> <datetime template second of day> ::=
> SSSSS
> <datetime template fraction> ::=
> FF1 | FF2 | FF3 | FF4 | FF5 | FF6 | FF7 | FF8 | FF9
> <datetime template am/pm> ::=
> A.M. | P.M.
> <datetime template time zone hour> ::=
> TZH
> <datetime template time zone minute> ::=
> TZM
> {noformat}
> SQL:2016 also introduced the {{FORMAT}} clause for {{CAST}} which is the
> standard way to do string <> datetime conversions
> {noformat}
> <cast specification> ::=
> CAST <left paren>
> <cast operand> AS <cast target>
> [ FORMAT <cast template> ]
> <right paren>
> <cast operand> ::=
> <value expression>
> | <implicitly typed value specification>
> <cast target> ::=
> <domain name>
> | <data type>
> <cast template> ::=
> <character string literal>
> {noformat}
> For example:
> {noformat}
> CAST(<datetime> AS <char string type> [FORMAT <template>])
> CAST(<char string> AS <datetime type> [FORMAT <template>])
> cast(dt as string format 'DD-MM-YYYY')
> {noformat}
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