kasakrisz commented on code in PR #5681:
URL: https://github.com/apache/hive/pull/5681#discussion_r1986773610
##########
parser/src/java/org/apache/hadoop/hive/ql/parse/IdentifiersParser.g:
##########
@@ -341,24 +341,47 @@ castExpression
-> ^(TOK_FUNCTION {adaptor.create(Identifier, "cast_format")}
NumberLiteral[Integer.toString(((CommonTree)toType.getTree()).token.getType())]
expression StringLiteral
NumberLiteral[((CommonTree)toType.getTree()).getChild(0).getText()])
;
-caseExpression
+whenExpression
@init { gParent.pushMsg("case expression", state); }
@after { gParent.popMsg(state); }
:
- KW_CASE expression
- (KW_WHEN expression KW_THEN expression)+
+ KW_CASE
+ ( KW_WHEN expression KW_THEN expression)+
(KW_ELSE expression)?
- KW_END -> ^(TOK_FUNCTION KW_CASE expression*)
+ KW_END -> ^(TOK_FUNCTION KW_WHEN expression*)
;
-whenExpression
+// Make caseExpression to build a whenExpression tree
+// Rewrite
+// CASE a
+// WHEN b THEN c
+// [WHEN d THEN e]* [ELSE f]
+// END
+// to
+// CASE
+// WHEN a=b THEN c
+// [WHEN a=d THEN e]* [ELSE f]
+// END
+caseExpression
@init { gParent.pushMsg("case expression", state); }
@after { gParent.popMsg(state); }
:
- KW_CASE
- ( KW_WHEN expression KW_THEN expression)+
- (KW_ELSE expression)?
- KW_END -> ^(TOK_FUNCTION KW_WHEN expression*)
+ KW_CASE caseOperand=expression
+ // Pass the case operand to the rule parses the when branches
+ whenBranches[$caseOperand.tree]
+ (KW_ELSE elseResult=expression)?
+ KW_END -> ^(TOK_FUNCTION Identifier["when"] whenBranches $elseResult?)
Review Comment:
I found that the rule `whenExpression` uses `KW_WHEN` but in that case the
left side of the rule definition also has `KW_WHEN`.
However the new `caseExpression` does not contain `KW_WHEN` explicitly.
Based on my current knowledge it makes sense to use `Identifier["when"]`.
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