zabetak commented on code in PR #5681:
URL: https://github.com/apache/hive/pull/5681#discussion_r1984798935
##########
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:
Is there any reason why we use `Identifier["when"]` instead of `KW_WHEN` in
the rewrite rule?
##########
ql/src/test/queries/clientpositive/cbo_case_when_type_conversion.q:
##########
@@ -0,0 +1,17 @@
+CREATE TABLE t1 (col1 char(3));
+
+INSERT INTO t1 VALUES ('A'),('b'),('c'),(null);
+
+explain cbo
+select col1, case upper(col1) when 'A' then 'OK' else 'N/A' end as col2 from
t1;
+explain
+select col1, case upper(col1) when 'A' then 'OK' else 'N/A' end as col2 from
t1;
+
+select col1, case upper(col1) when 'A' then 'OK' else 'N/A' end as col2 from
t1;
+
+select col1,
Review Comment:
What's the test goal of this query?
##########
ql/src/test/results/clientpositive/llap/order_by_expr_2.q.out:
##########
@@ -139,7 +139,7 @@ POSTHOOK: Input: default@store
CBO PLAN:
HiveProject(c0=[$0], c1=[$1], c2=[$2])
HiveSortLimit(sort0=[$3], dir0=[ASC])
- HiveProject(c0=[$0], c1=[$1], c2=[$2], (tok_function case
(tok_table_or_col store_name) 'HQ' tok_null (tok_table_or_col store_name))=[$1])
+ HiveProject(c0=[$0], c1=[$1], c2=[$2], (tok_function when (=
(tok_table_or_col store_name) 'HQ') tok_null (tok_table_or_col
store_name))=[$1])
Review Comment:
It took me a few minutes to understand that this is an alias that is
identical to AST :)
##########
ql/src/test/queries/clientpositive/cbo_case_when_type_conversion.q:
##########
@@ -0,0 +1,17 @@
+CREATE TABLE t1 (col1 char(3));
+
+INSERT INTO t1 VALUES ('A'),('b'),('c'),(null);
+
+explain cbo
+select col1, case upper(col1) when 'A' then 'OK' else 'N/A' end as col2 from
t1;
Review Comment:
Since we added a rewrite rule for `CASE x WHEN y` to `CASE WHEN x=y` I would
expect to add an identical query using the other syntax and show that plans and
results are the same.
##########
ql/src/test/queries/clientpositive/cbo_case_when_type_conversion.q:
##########
@@ -0,0 +1,17 @@
+CREATE TABLE t1 (col1 char(3));
+
+INSERT INTO t1 VALUES ('A'),('b'),('c'),(null);
Review Comment:
Since we use check upper with 'A' in the queries below it would make more
sense to have 'a' in the data otherwise the `upper` call is more or less a
noop. Respectively for `lower` and comparison with `b`.
In fact to simplify a bit the test we could just use upper or lower in both
queries.
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