wnob commented on code in PR #2973:
URL: https://github.com/apache/calcite/pull/2973#discussion_r1025778875
##########
babel/src/main/codegen/includes/parserImpls.ftl:
##########
@@ -42,6 +42,26 @@ SqlNode DateFunctionCall() :
}
}
+SqlNode TimestampFunctionCall() :
Review Comment:
Here's my understanding: Babel is the "universal" parser ¹ that does not
understand the semantics of individual dialects (hence the name).
Dialect-specific semantic validation is a separate step that occurs after
dialect-agnostic parsing.
This is a [FreeMarker template file][1]. It does not contain any
interpolation or tags, so running this through FreeMarker would simply remove
the license comment at the top of the file. It's processed by [FMPP][2] in
`config.fmpp` [here][3], which is in-turn referenced in the [JavaCC][4] grammar
[here][5], as well as [here][6] via the `builtinFunctionCallMethods` list where
the function name was added above in `config.fmpp`.
Together, these 2 additions to the grammar indicate that there is a
*production* called `TimestampFunctionCall` which consists of the
[`<TIMESTAMP>` token][7] followed by a [`FunctionParameterList`][8] production,
which consists of left-parenthesis, comma-separated arguments,
right-parenthesis. The parser does nothing to validate how many arguments there
are or what types they are.
So yes, long story short, you're right that we didn't have to modify the
`DateFunctionCall` production because it's just a function call either way, and
I just added this new production with a different name token but which is
otherwise identical to the `DATE` one.
¹ I've heard Julian make reference to other parsers being potentially usable
with Calcite but I don't know of any examples.
[1]: https://freemarker.apache.org/docs/dgui_template_overallstructure.html
[2]: https://fmpp.sourceforge.net/index.html
[3]:
https://github.com/apache/calcite/blob/a505b25eacc473c6ec0ef8abd40c1ccae86297b6/babel/src/main/codegen/config.fmpp#L566
[4]: https://javacc.github.io/javacc/
[5]:
https://github.com/apache/calcite/blob/a0e119ea42def418957f214f539469f1aba76c18/core/src/main/codegen/templates/Parser.jj#L1163
[6]:
https://github.com/apache/calcite/blob/a0e119ea42def418957f214f539469f1aba76c18/core/src/main/codegen/templates/Parser.jj#L5992
[7]:
https://github.com/apache/calcite/blob/a0e119ea42def418957f214f539469f1aba76c18/core/src/main/codegen/templates/Parser.jj#L7922
[8]:
https://github.com/apache/calcite/blob/a0e119ea42def418957f214f539469f1aba76c18/core/src/main/codegen/templates/Parser.jj#L948
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