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https://issues.apache.org/jira/browse/TRAFODION-1673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15376157#comment-15376157
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ASF GitHub Bot commented on TRAFODION-1673:
-------------------------------------------
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.
> Implement the WITH clause in Trafodion SQL for simple use cases
> ---------------------------------------------------------------
>
> Key: TRAFODION-1673
> URL: https://issues.apache.org/jira/browse/TRAFODION-1673
> Project: Apache Trafodion
> Issue Type: New Feature
> Components: sql-cmp
> Reporter: Hans Zeller
> Assignee: liu ming
>
> We keep running into queries that use a WITH clause to define a temporary
> view that can be used once or multiple times in a FROM clause in the query.
> For non-recursive queries, the WITH clause could probably be handled very
> similar to a view. When it is defined, we create an in-memory view
> descriptor, containing the name and the definition. When it is used in a FROM
> clause, we could go through a code path similar to that of a view - bind the
> (temporary) view text and substitute it in the query. The fix could probably
> be handled entirely in the binder.
> This JIRA is *not* about recursive queries, those would require a lot more
> effort, involving many components in addition to the binder.
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