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https://issues.apache.org/jira/browse/CALCITE-5352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17626908#comment-17626908
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carton.swing commented on CALCITE-5352:
---------------------------------------
[~libenchao] If you run this statement in psql(PostgreSQL Client):
{code:java}
postgres=# SELECT EXTRACT(WEEK FROM TIMESTAMP '2022-10-31');
extract
---------
44
(1 row)
postgres=# SELECT DATE_PART(WEEK, TIMESTAMP '2022-10-31');
ERROR: column "week" does not exist
LINE 1: SELECT DATE_PART(WEEK, TIMESTAMP '2022-10-31');
{code}
you will get an error because PostgreSQL only accept text field with DATE_PART
function for the first argument. But in EXTRACT function, the argument can be
both a quoted string or identifier.
But I wonder if current support for DATE_PART function is only for redshift
cause I found this comment in test file:
[https://github.com/apache/calcite/blob/calcite-1.32.0/babel/src/test/java/org/apache/calcite/test/BabelParserTest.java#L175~L177]
{code:java}
/** In Redshift, PostgreSQL the DATEADD, DATEDIFF and DATE_PART functions have
* ordinary function syntax except that its first argument is a time unit *
(e.g. DAY). We must not parse that first argument as an identifier. */ {code}
> Babel parser does not recognize character literal with DATE_PART function
> -------------------------------------------------------------------------
>
> Key: CALCITE-5352
> URL: https://issues.apache.org/jira/browse/CALCITE-5352
> Project: Calcite
> Issue Type: Bug
> Reporter: carton.swing
> Priority: Major
>
> While using babel parser(calcite-babel's SqlBabelParserImpl) to parse
> PostgreSQL syntax:
> {code:java}
> planner.parse("SELECT DATE_PART('week', TIMESTAMP '2022-10-31')"){code}
> it will throws exception.
> But if I use:
> {code:java}
> planner.parse("SELECT DATE_PART(week, TIMESTAMP '2022-10-31')"){code}
> the parser works well.
>
> However, the former syntax, which is a quote-string, is correct according to
> : [https://www.postgresql.org/docs/9.1/functions-datetime.html]
> |Note that here the {{field}} parameter needs to be a string value, not a
> name. The valid field names for {{date_part}} are the same as for
> {{{}extract{}}}.
> SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40');|
> The first argument should be a quote string instead of a TimeUnit token.
>
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