[jira] [Created] (CALCITE-4972) Qualify subfields of array columns containing structs in return of getFieldOrigins

["Mark Grey (Jira)" <ji...@apache.org>]

Mark Grey created CALCITE-4972:
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             Summary: Qualify subfields of array columns containing structs in return of getFieldOrigins
                 Key: CALCITE-4972
                 URL: https://issues.apache.org/jira/browse/CALCITE-4972
             Project: Calcite
          Issue Type: Improvement
          Components: core
    Affects Versions: 1.28.0
            Reporter: Mark Grey


Attempting to follow on the [suggestions from Julian in this thread|https://lists.apache.org/thread/pdpqtzy5mtzlpdbhwghbty6cj0jgc86l], found a potential improvement.

Given a table schema containing a repeated array of structs and a query projecting fields of that struct via UNNEST, the present implementation of {{getFieldOrigins}} in {{SqlValidatorImpl}} will return a list representation suggesting that the subfield is actually a member of the top level table row type.

For example, when using the [DEPT_NESTED table from the MockCatalogReaderSimple|https://github.com/apache/calcite/blob/master/testkit/src/main/java/org/apache/calcite/test/catalog/MockCatalogReaderSimple.java#L152-L159] within tests with the following query:

{code:sql}
select e.empno from dept_nested, unnest(employees) as e
{code}

The return value will be:

{code}
{CATALOG.SALES.DEPT_NESTED.EMPNO}
{code}

Rather than:

{code}
{CATALOG.SALES.DEPT_NESTED.EMPLOYEES.EMPNO}
{code}

No such column  {{EMPNO}} exists in the root schema of the DEPT_NESTED table.  [The javadoc for the method |https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql/validate/SqlValidator.java#L717-L728]however suggests that the return from this method should always be four entries long, although it would seem this doesn't account for nesting.  Is this intended behavior, or should {{column}} entry of this list be of variable length? 



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