Github user traflm commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/577#discussion_r70736959
--- Diff: core/sql/parser/sqlparser.y ---
@@ -14684,6 +14759,11 @@ optional_limit_spec : TOK_LIMIT
NUMERIC_LITERAL_EXACT_NO_SCALE
dml_statement : dml_query { $$ = $1; }
+ | with_clause_list dml_query
--- End diff --
I found a way to avoid the reduce/shift and reduce/reduce error by add
with_clause down to the underlying rules of non_join_query_expression, instead
of add it at same level of non_join_query_expression. non_join_query_expression
can represent many different styles of query expression, including utilities,
which we don't want a with_clause as prefix, so in the underlying rules, only
add with_clause before those SELECT syntax, and it solve the problem.
And it seems if use redundant rule explicitly (looks annoying) , we can
avoid the error.
For example:
A : b | c
is better to change to
A : b
A : c
I am still trying to understand this.
I checked with PostgreSQL parser, they are doing similar things, comments
from postgresql parser:
* This rule parses the equivalent of the standard's <query expression>.
* The duplicative productions are annoying, but hard to get rid of without
* creating shift/reduce conflicts.
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