[jira] [Created] (CALCITE-3379) Support expand atom expression in table to relational node conversion

["Danny Chen (Jira)" <ji...@apache.org>]

Danny Chen created CALCITE-3379:
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             Summary: Support expand atom expression in table to relational node conversion
                 Key: CALCITE-3379
                 URL: https://issues.apache.org/jira/browse/CALCITE-3379
             Project: Calcite
          Issue Type: Improvement
          Components: core
    Affects Versions: 1.21.0
            Reporter: Danny Chen
            Assignee: Danny Chen
             Fix For: 1.22.0


Now there are 2 ways to convert a RelOptTable to LogicalTableScan:

1. One way is tp open the Config#sConvertTableAccess[1] flag and the SqlToRelConverter would invoke the #toRel method which transforms the table to a node returned by the user(Usually a table scan).

2. Another way it to use the LogicalTableScan rule, this rule would invoke RelOptTable#toRel and wrap the returned node with a LogicalTableScan.

 

The different between 1 and 2 is that, 2 happens in the planning rule but 1 happens in sql-to-rel conversion, 1 also supports to expand the table columns based on the defined default values expressions, see InitializerExpressionFactory#newColumnDefaultValue.

 

The problem with the InitializerExpressionFactory#newColumnDefaultValue is that it use InitializerContext#convertExpression to convert a SqlNode, if the SqlNode is not validated, we always got a RexCall with SqlUnresolvedFunction. We should give the user change to validate their SqlNode or even we can support pure string expressions because they can be used to persist.

 

Another problem with #toRel is that after the expressions applied as a projection, use has no change to apply any other rel nodes if they want, we can actually support this, the same way as we support the column expressions.

 

[1]https://github.com/apache/calcite/blob/2dc97e6723e1b5bf762540f87ffffb5cd1a848a1/core/src/main/java/org/apache/calcite/sql2rel/SqlToRelConverter.java#L5605



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