org.apache.calcite.sql2rel

Interface InitializerContext

All Known Implementing Classes:

SqlToRelConverter.Blackboard

public interface InitializerContext

Provides context for InitializerExpressionFactory methods.

Method Summary

Modifier and Type	Method and Description
RexNode	convertExpression(SqlNode expr) Converts a SqlNode to RexNode.
RexBuilder	getRexBuilder()
default SqlNode	parseExpression(SqlParser.Config config, String expr) Parse a column computation expression for a table.
SqlNode	validateExpression(RelDataType rowType, SqlNode expr) Validate the expression with a base table row type.

Method Detail

getRexBuilder

RexBuilder getRexBuilder()

parseExpression

default SqlNode parseExpression(SqlParser.Config config,
                                String expr)

Parse a column computation expression for a table. Usually this expression is declared in the create table statement, i.e.

   create table t(
     a int not null,
     b varchar(5) as (my_udf(a)) virtual,
     c int not null as (a + 1)
   );
 

You can use the string format expression "my_udf(a)" and "a + 1" as the initializer expression of column b and c.

Calcite doesn't really need this now because the DDL nodes can be executed directly from SqlNodes, but we still provide the way to initialize from a SQL-like string, because a string can be used to persist easily and the column expressions are important part of the table metadata.

Parameters:

config - parse config

expr - the SQL-style column expression

Returns:

a SqlNode instance

validateExpression

SqlNode validateExpression(RelDataType rowType,
                           SqlNode expr)

Validate the expression with a base table row type. The expression may reference the fields of the row type defines.

Parameters:

rowType - the table row type

expr - the expression

Returns:

a validated SqlNode, usually it transforms from a SqlUnresolvedFunction to a resolved one

convertExpression

RexNode convertExpression(SqlNode expr)

Converts a SqlNode to RexNode.

Caution that the SqlNode must be validated, you can use validateExpression(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.sql.SqlNode) to validate if the SqlNode is un-validated.

Parameters:

expr - the expression of sql node to convert

Returns:

a converted RexNode instance