org.apache.calcite.rel.rules

Class ReduceDecimalsRule

java.lang.Object

org.apache.calcite.plan.RelOptRule

org.apache.calcite.rel.rules.ReduceDecimalsRule

public class ReduceDecimalsRule
extends RelOptRule

ReduceDecimalsRule is a rule which reduces decimal operations (such as casts or arithmetic) into operations involving more primitive types (such as longs and doubles). The rule allows Calcite implementations to deal with decimals in a consistent manner, while saving the effort of implementing them.

The rule can be applied to a LogicalCalc with a program for which RexUtil.requiresDecimalExpansion(org.apache.calcite.rex.RexNode, boolean) returns true. The rule relies on a RexShuttle to walk over relational expressions and replace them.

While decimals are generally not implemented by the Calcite runtime, the rule is optionally applied, in order to support the situation in which we would like to push down decimal operations to an external database.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	ReduceDecimalsRule.DecimalShuttle A shuttle which converts decimal expressions to expressions based on longs.
class	ReduceDecimalsRule.RexExpander Rewrites a decimal expression for a specific set of SqlOperator's.

Field Summary

Fields

Modifier and Type	Field and Description
static ReduceDecimalsRule	INSTANCE

Fields inherited from class org.apache.calcite.plan.RelOptRule

description, operands

Method Summary

Methods

Modifier and Type	Method and Description
Convention	getOutConvention() Returns the convention of the result of firing this rule, null if not known.
void	onMatch(RelOptRuleCall call) Receives notification about a rule match.

Methods inherited from class org.apache.calcite.plan.RelOptRule

any, convert, convert, convertList, equals, equals, getOperand, getOperands, getOutTrait, hashCode, matches, none, operand, operand, operand, operand, operand, some, toString, unordered

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

INSTANCE

public static final ReduceDecimalsRule INSTANCE

Method Detail

getOutConvention

public Convention getOutConvention()

Description copied from class: RelOptRule

Returns the convention of the result of firing this rule, null if not known.

Overrides:

getOutConvention in class RelOptRule

Returns:

Convention of the result of firing this rule, null if not known

onMatch

public void onMatch(RelOptRuleCall call)

Description copied from class: RelOptRule

Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.apache.calcite.rel.RelNode, java.util.Map<org.apache.calcite.rel.RelNode, org.apache.calcite.rel.RelNode>) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

call - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)