[I] UNION ALL should strip table identifiers in its resulting schema [datafusion]

[via GitHub]

phillipleblanc opened a new issue, #10706:
URL: https://github.com/apache/datafusion/issues/10706

   ### Describe the bug
   
   The schema that is the result of a UNION ALL should not have any table 
qualifiers, as the table information has effectively been erased and is no 
longer a valid reference.
   
   Consider the following SQL:
   
   ```sql
   SELECT table1.foo FROM table1
   UNION ALL
   SELECT table2.foo FROM table2
   ```
   
   The logical schema from this UNION ALL should be just `foo`, but it is 
currently taking the first input's schema directly, resulting in a schema of 
`table1.foo`.
   
   This came up as an issue when trying to validate the unparser works 
correctly for UNION ALL statements, which I added in 
https://github.com/apache/datafusion/pull/10603
   
   Slightly modifying the above example, if I add an ORDER BY clause to the 
input SQL:
   
   ```sql
   SELECT table1.foo FROM table1
   UNION ALL
   SELECT table2.foo FROM table2
   ORDER BY foo
   ```
   
   Then the resulting unparsed SQL will be:
   
   ```sql
   SELECT table1.foo FROM table1
   UNION ALL
   SELECT table2.foo FROM table2
   ORDER BY table1.foo
   ```
   
   Because the unparser takes the schema directly from the Union node when 
writing out the column expressions.
   
   ### To Reproduce
   
   Running this test fails, when it should succeed:
   
   ```
   #[test]
   fn roundtrip_statement_with_dialect() -> Result<()> {
       struct TestStatementWithDialect {
           sql: &'static str,
           expected: &'static str,
           parser_dialect: Box<dyn Dialect>,
           unparser_dialect: Box<dyn UnparserDialect>,
       }
       let tests: Vec<TestStatementWithDialect> = vec![
           TestStatementWithDialect {
               sql: "SELECT j1_id FROM j1
                     UNION ALL
                     SELECT tb.j2_id as j1_id FROM j2 tb
                     ORDER BY j1_id
                     LIMIT 10;",
               expected: r#"SELECT j1.j1_id FROM j1 UNION ALL SELECT tb.j2_id 
AS j1_id FROM j2 AS tb ORDER BY j1_id ASC NULLS LAST LIMIT 10"#,
               parser_dialect: Box::new(GenericDialect {}),
               unparser_dialect: Box::new(UnparserDefaultDialect {}),
           },
       ];
   
       for query in tests {
           let statement = Parser::new(&*query.parser_dialect)
               .try_with_sql(query.sql)?
               .parse_statement()?;
   
           let context = MockContextProvider::default();
           let sql_to_rel = SqlToRel::new(&context);
           let plan = sql_to_rel
               .sql_statement_to_plan(statement)
               .unwrap_or_else(|e| panic!("Failed to parse sql: {}\n{e}", 
query.sql));
   
           let unparser = Unparser::new(&*query.unparser_dialect);
           let roundtrip_statement = unparser.plan_to_sql(&plan)?;
   
           let actual = format!("{}", &roundtrip_statement);
           println!("roundtrip sql: {actual}");
           println!("plan {}", plan.display_indent());
   
           assert_eq!(query.expected, actual);
       }
   
       Ok(())
   }
   ```
   
   ### Expected behavior
   
   The table qualifiers are stripped from the schema of a UNION ALL LogicalPlan 
node.
   
   ### Additional context
   
   _No response_


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org.apache.org

For queries about this service, please contact Infrastructure at:
us...@infra.apache.org


---------------------------------------------------------------------
To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org
For additional commands, e-mail: github-h...@datafusion.apache.org