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https://issues.apache.org/jira/browse/CALCITE-3379?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Danny Chen updated CALCITE-3379:
--------------------------------
Description:
Now there are 2 ways to convert a RelOptTable to LogicalTableScan:
1. One way is to open the Config#isConvertTableAccess[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 is to use the LogicalTableScan rule, this rule would invoke
RelOptTable#toRel and wrap the returned node with a LogicalTableScan.
The difference 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 uses InitializerContext#convertExpression to convert a SqlNode, but if the
SqlNode is not validated, we always got a RexCall with SqlUnresolvedFunction.
We should give the user chance to validate their SqlNode or even we can support
pure string expressions which can be used to persist.
Another problem with #toRel is that after the expressions applied as a
projection, user has no chance to apply any other relational 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
was:
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
> 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
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.22.0
>
> Time Spent: 2h
> Remaining Estimate: 0h
>
> Now there are 2 ways to convert a RelOptTable to LogicalTableScan:
> 1. One way is to open the Config#isConvertTableAccess[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 is to use the LogicalTableScan rule, this rule would invoke
> RelOptTable#toRel and wrap the returned node with a LogicalTableScan.
>
> The difference 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 uses InitializerContext#convertExpression to convert a SqlNode, but
> if the SqlNode is not validated, we always got a RexCall with
> SqlUnresolvedFunction. We should give the user chance to validate their
> SqlNode or even we can support pure string expressions which can be used to
> persist.
>
> Another problem with #toRel is that after the expressions applied as a
> projection, user has no chance to apply any other relational 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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