org.apache.calcite.rel.rules

Class PushProjector

java.lang.Object

org.apache.calcite.rel.rules.PushProjector

public class PushProjector
extends Object

PushProjector is a utility class used to perform operations used in push projection rules.

Pushing is particularly interesting in the case of join, because there are multiple inputs. Generally an expression can be pushed down to a particular input if it depends upon no other inputs. If it can be pushed down to both sides, it is pushed down to the left.

Sometimes an expression needs to be split before it can be pushed down. To flag that an expression cannot be split, specify a rule that it must be preserved. Such an expression will be pushed down intact to one of the inputs, or not pushed down at all.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	PushProjector.ExprCondition A functor that replies true or false for a given expression.
static class	PushProjector.OperatorExprCondition An expression condition that evaluates to true if the expression is a call to one of a set of operators.

Constructor Summary

Constructors

Constructor and Description
PushProjector(LogicalProject origProj, RexNode origFilter, RelNode childRel, PushProjector.ExprCondition preserveExprCondition) Creates a PushProjector object for pushing projects past a RelNode.

Method Summary

Methods

Modifier and Type	Method and Description
RelNode	convertProject(RexNode defaultExpr) Decomposes a projection to the input references referenced by a projection and a filter, either of which is optional.
RexNode	convertRefsAndExprs(RexNode rex, List<RelDataTypeField> destFields, int[] adjustments) Clones an expression tree and walks through it, adjusting each RexInputRef index by some amount, and converting expressions that need to be preserved to field references.
RelNode	createNewProject(RelNode projChild, int[] adjustments) Creates a new projection based on the original projection, adjusting all input refs using an adjustment array passed in.
LogicalProject	createProjectRefsAndExprs(RelNode projChild, boolean adjust, boolean rightSide) Creates a projection based on the inputs specified in a bitmap and the expressions that need to be preserved.
int[]	getAdjustments() Determines how much each input reference needs to be adjusted as a result of projection
boolean	locateAllRefs() Locates all references found in either the projection expressions a filter, as well as references to expressions that should be preserved.

Methods inherited from class java.lang.Object

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

Constructor Detail

PushProjector

public PushProjector(LogicalProject origProj,
             RexNode origFilter,
             RelNode childRel,
             PushProjector.ExprCondition preserveExprCondition)

Creates a PushProjector object for pushing projects past a RelNode.

Parameters:

origProj - the original projection that is being pushed; may be null if the projection is implied as a result of a projection having been trivially removed

origFilter - the filter that the projection must also be pushed past, if applicable

childRel - the RelNode that the projection is being pushed past

preserveExprCondition - condition for whether an expression should be preserved in the projection

Method Detail

convertProject

public RelNode convertProject(RexNode defaultExpr)

Decomposes a projection to the input references referenced by a projection and a filter, either of which is optional. If both are provided, the filter is underneath the project.

Creates a projection containing all input references as well as preserving any special expressions. Converts the original projection and/or filter to reference the new projection. Then, finally puts on top, a final projection corresponding to the original projection.

Parameters:

defaultExpr - expression to be used in the projection if no fields or special columns are selected

Returns:

the converted projection if it makes sense to push elements of the projection; otherwise returns null

locateAllRefs

public boolean locateAllRefs()

Locates all references found in either the projection expressions a filter, as well as references to expressions that should be preserved. Based on that, determines whether pushing the projection makes sense.

Returns:

true if all inputs from the child that the projection is being pushed past are referenced in the projection/filter and no special preserve expressions are referenced; in that case, it does not make sense to push the projection

createProjectRefsAndExprs

public LogicalProject createProjectRefsAndExprs(RelNode projChild,
                                       boolean adjust,
                                       boolean rightSide)

Creates a projection based on the inputs specified in a bitmap and the expressions that need to be preserved. The expressions are appended after the input references.

Parameters:

projChild - child that the projection will be created on top of

adjust - if true, need to create new projection expressions; otherwise, the existing ones are reused

rightSide - if true, creating a projection for the right hand side of a join

Returns:

created projection

getAdjustments

public int[] getAdjustments()

Determines how much each input reference needs to be adjusted as a result of projection

Returns:

array indicating how much each input needs to be adjusted by

convertRefsAndExprs

public RexNode convertRefsAndExprs(RexNode rex,
                          List<RelDataTypeField> destFields,
                          int[] adjustments)

Clones an expression tree and walks through it, adjusting each RexInputRef index by some amount, and converting expressions that need to be preserved to field references.

Parameters:

rex - the expression

destFields - fields that the new expressions will be referencing

adjustments - the amount each input reference index needs to be adjusted by

Returns:

modified expression tree

createNewProject

public RelNode createNewProject(RelNode projChild,
                       int[] adjustments)

Creates a new projection based on the original projection, adjusting all input refs using an adjustment array passed in. If there was no original projection, create a new one that selects every field from the underlying rel.

If the resulting projection would be trivial, return the child.

Parameters:

projChild - child of the new project

adjustments - array indicating how much each input reference should be adjusted by

Returns:

the created projection