Package org.apache.calcite.rel.core

Class Snapshot

java.lang.Object

org.apache.calcite.rel.AbstractRelNode

org.apache.calcite.rel.SingleRel

org.apache.calcite.rel.core.Snapshot

All Implemented Interfaces:

java.lang.Cloneable, RelOptNode, RelNode

Direct Known Subclasses:

LogicalSnapshot

public abstract class Snapshot
extends SingleRel

Relational expression that returns the contents of a relation expression as it was at a given time in the past.

For example, if Products is a temporal table, and TableScan(Products) is a relational operator that returns all versions of the contents of the table, then Snapshot(TableScan(Products)) is a relational operator that only returns the contents whose versions that overlap with the given specific period (i.e. those that started before given period and ended after it).

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.calcite.rel.RelNode

RelNode.Context

Field Summary

Fields

Modifier and Type	Field	Description
private RexNode	period

Fields inherited from class org.apache.calcite.rel.SingleRel

input

Fields inherited from class org.apache.calcite.rel.AbstractRelNode

digest, id, rowType, traitSet

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Snapshot(RelOptCluster cluster, RelTraitSet traitSet, RelNode input, RexNode period)	Creates a Snapshot.

Method Summary

Modifier and Type	Method	Description
RelNode	accept(RexShuttle shuttle)	Accepts a visit from a shuttle.
RelNode	copy(RelTraitSet traitSet, java.util.List<RelNode> inputs)	Creates a copy of this relational expression, perhaps changing traits and inputs.
abstract Snapshot	copy(RelTraitSet traitSet, RelNode input, RexNode period)
RelWriter	explainTerms(RelWriter pw)	Describes the inputs and attributes of this relational expression.
java.util.List<RexNode>	getChildExps()	Returns a list of this relational expression's child expressions.
RexNode	getPeriod()
boolean	isValid(Litmus litmus, RelNode.Context context)	Returns whether this relational expression is valid.

Methods inherited from class org.apache.calcite.rel.SingleRel

childrenAccept, deriveRowType, estimateRowCount, getInput, getInputs, replaceInput

Methods inherited from class org.apache.calcite.rel.AbstractRelNode

accept, collectVariablesSet, collectVariablesUsed, computeDigest, computeSelfCost, computeSelfCost, equals, explain, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getQuery, getRelTypeName, getRows, getRowType, getTable, getTraitSet, getVariablesSet, getVariablesStopped, hashCode, isDistinct, isKey, isValid, metadata, onRegister, recomputeDigest, register, sole, toString

Methods inherited from class java.lang.Object

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

Field Detail

period

private final RexNode period

Constructor Detail

Snapshot

protected Snapshot(RelOptCluster cluster,
                   RelTraitSet traitSet,
                   RelNode input,
                   RexNode period)

Creates a Snapshot.

Parameters:

cluster - Cluster that this relational expression belongs to

traitSet - The traits of this relational expression

input - Input relational expression

period - Timestamp expression which as the table was at the given time in the past

Method Detail

copy

public final RelNode copy(RelTraitSet traitSet,
                          java.util.List<RelNode> inputs)

Description copied from interface: RelNode

Creates a copy of this relational expression, perhaps changing traits and inputs.

Sub-classes with other important attributes are encouraged to create variants of this method with more parameters.

Specified by:

copy in interface RelNode

Overrides:

copy in class AbstractRelNode

Parameters:

traitSet - Trait set

inputs - Inputs

Returns:

Copy of this relational expression, substituting traits and inputs

copy

public abstract Snapshot copy(RelTraitSet traitSet,
                              RelNode input,
                              RexNode period)

getChildExps

public java.util.List<RexNode> getChildExps()

Description copied from interface: RelNode

Returns a list of this relational expression's child expressions. (These are scalar expressions, and so do not include the relational inputs that are returned by RelNode.getInputs().

The caller should treat the list as unmodifiable; typical implementations will return an immutable list. If there are no child expressions, returns an empty list, not null.

Specified by:

getChildExps in interface RelNode

Overrides:

getChildExps in class AbstractRelNode

Returns:

List of this relational expression's child expressions

See Also:

RelNode.accept(org.apache.calcite.rex.RexShuttle)

accept

public RelNode accept(RexShuttle shuttle)

Description copied from interface: RelNode

Accepts a visit from a shuttle. If the shuttle updates expression, then a copy of the relation should be created. This new relation might have a different row-type.

Specified by:

accept in interface RelNode

Overrides:

accept in class AbstractRelNode

Parameters:

shuttle - Shuttle

Returns:

A copy of this node incorporating changes made by the shuttle to this node's children

explainTerms

public RelWriter explainTerms(RelWriter pw)

Description copied from class: AbstractRelNode

Describes the inputs and attributes of this relational expression. Each node should call super.explainTerms, then call the RelWriter.input(String, RelNode) and RelWriterImpl.item(String, Object) methods for each input and attribute.

Overrides:

explainTerms in class SingleRel

Parameters:

pw - Plan writer

Returns:

Plan writer for fluent-explain pattern

getPeriod

public RexNode getPeriod()

isValid

public boolean isValid(Litmus litmus,
                       RelNode.Context context)

Description copied from interface: RelNode

Returns whether this relational expression is valid.

If assertions are enabled, this method is typically called with litmus = THROW, as follows:

assert rel.isValid(Litmus.THROW)

This signals that the method can throw an AssertionError if it is not valid.

Specified by:

isValid in interface RelNode

Overrides:

isValid in class AbstractRelNode

Parameters:

litmus - What to do if invalid

context - Context for validity checking

Returns:

Whether relational expression is valid