[CALCITE-1003] Add Utility to convert RelNode to SqlNode

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.6.0
• Component/s: core
• Assignee: Julian Hyde
• Reporter: Amogh Margoor
• Created: 03/Dec/15 06:56
• Updated: 27/Jan/17 22:57
• Resolved: 10/Dec/15 04:59

Description

To track progress on Rel2Sql Converter.
Following is the email conversation that lead to this JIRA:

On Wed, Dec 2, 2015 at 3:13 AM, Julian Hyde <[e-mail]> wrote:

Yes, this would definitely be useful in Calcite. Thanks for offering.

I would like to reduce the amount of code copy-pasted from the JdbcXxx relational expressions, but we can work on that after it is committed in and when there are some unit tests.

Can you please create a JIRA case with an initial pull-request?

I think the unit tests could be of the following form:

      @Test public void testScan() {
        final String sql = “select * from emp”;
        final String after = "SELECT *\n”
            + "FROM \”EMP\””;
        check(sql, after);
      }

where “after” is the result of the round trip SQL => SqlNode => RelNode => SqlNode => SQL, and your utility is performing the 3rd “=>”.

Julian

> On Dec 1, 2015, at 12:28 AM, Amogh Margoor <[e-mail]> wrote:
>
> Hi,
> We have an usecase where we need to just send back optimized query as SQL,
> without executing it. So we needed an utility to convert RelNode back to
> SQL, and found most of the logic to be in JDBCRel. As we needed it for non
> JDBC source, we created an utility to do so:
> https://github.com/amoghmargoor/incubator-calcite/blob/NEZ-52/core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java
>
> Utility is almost completely copy-pasted from JDBCRels with few fixes from
> our side to make it work. If such utility will be useful in Calcite then
> let us know, we can plan raising PRs with required UTs.
>
> Regards,
> Amogh

Issue Links

• is depended upon by: CALCITE-1010 Support FETCH/LIMIT and OFFSET in RelToSqlConverter
• is related to: CALCITE-1607 RelToSqlConverter assertion error with projection over sort
• links to: PR 174