org.apache.calcite.sql2rel

Class NullInitializerExpressionFactory

java.lang.Object

org.apache.calcite.sql2rel.NullInitializerExpressionFactory

All Implemented Interfaces:

InitializerExpressionFactory

public class NullInitializerExpressionFactory
extends Object
implements InitializerExpressionFactory

An implementation of InitializerExpressionFactory that always supplies NULL.

Field Summary

Fields

Modifier and Type	Field and Description
static InitializerExpressionFactory	INSTANCE

Constructor Summary

Constructors

Constructor and Description
NullInitializerExpressionFactory()

Method Summary

Modifier and Type	Method and Description
ColumnStrategy	generationStrategy(RelOptTable table, int iColumn) Returns how a column is populated.
boolean	isGeneratedAlways(RelOptTable table, int iColumn) Whether a column is always generated.
RexNode	newAttributeInitializer(RelDataType type, SqlFunction constructor, int iAttribute, List<RexNode> constructorArgs, InitializerContext context) Creates an expression which evaluates to the initializer expression for a particular attribute of a structured type.
RexNode	newColumnDefaultValue(RelOptTable table, int iColumn, InitializerContext context) Creates an expression which evaluates to the default value for a particular column.
@Nullable BiFunction<InitializerContext,RelNode,RelNode>	postExpressionConversionHook() Creates a hook function to customize the relational expression right after the column expressions are converted.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INSTANCE

public static final InitializerExpressionFactory INSTANCE

Constructor Detail

NullInitializerExpressionFactory

public NullInitializerExpressionFactory()

Method Detail

isGeneratedAlways

public boolean isGeneratedAlways(RelOptTable table,
                                 int iColumn)

Description copied from interface: InitializerExpressionFactory

Whether a column is always generated. If a column is always generated, then non-generated values cannot be inserted into the column.

Specified by:

isGeneratedAlways in interface InitializerExpressionFactory

See Also:

InitializerExpressionFactory.generationStrategy(RelOptTable, int)

generationStrategy

public ColumnStrategy generationStrategy(RelOptTable table,
                                         int iColumn)

Description copied from interface: InitializerExpressionFactory

Returns how a column is populated.

Specified by:

generationStrategy in interface InitializerExpressionFactory

Parameters:

table - the table containing the column

iColumn - the 0-based offset of the column in the table

Returns:

generation strategy, never null

See Also:

RelOptTable.getColumnStrategies()

newColumnDefaultValue

public RexNode newColumnDefaultValue(RelOptTable table,
                                     int iColumn,
                                     InitializerContext context)

Description copied from interface: InitializerExpressionFactory

Creates an expression which evaluates to the default value for a particular column.

If the default value comes from a un-validated SqlNode, make sure to invoke InitializerContext.validateExpression(org.apache.calcite.rel.type.RelDataType, org.apache.calcite.sql.SqlNode) first before you actually do the conversion with method InitializerContext.convertExpression(org.apache.calcite.sql.SqlNode).

Specified by:

newColumnDefaultValue in interface InitializerExpressionFactory

Parameters:

table - the table containing the column

iColumn - the 0-based offset of the column in the table

context - Context for creating the expression

Returns:

default value expression

postExpressionConversionHook

public @Nullable BiFunction<InitializerContext,RelNode,RelNode> postExpressionConversionHook()

Description copied from interface: InitializerExpressionFactory

Creates a hook function to customize the relational expression right after the column expressions are converted. Usually the relational expression is a projection above a table scan.

Specified by:

postExpressionConversionHook in interface InitializerExpressionFactory

Returns:

a hook function to transform the relational expression right after the column expression conversion to a customized one

See Also:

InitializerExpressionFactory.newColumnDefaultValue(RelOptTable, int, InitializerContext)

newAttributeInitializer

public RexNode newAttributeInitializer(RelDataType type,
                                       SqlFunction constructor,
                                       int iAttribute,
                                       List<RexNode> constructorArgs,
                                       InitializerContext context)

Description copied from interface: InitializerExpressionFactory

Creates an expression which evaluates to the initializer expression for a particular attribute of a structured type.

Specified by:

newAttributeInitializer in interface InitializerExpressionFactory

Parameters:

type - the structured type

constructor - the constructor invoked to initialize the type

iAttribute - the 0-based offset of the attribute in the type

constructorArgs - arguments passed to the constructor invocation

context - Context for creating the expression

Returns:

default value expression