org.apache.calcite.rel.core

Class Sort

java.lang.Object

org.apache.calcite.rel.AbstractRelNode

org.apache.calcite.rel.SingleRel

org.apache.calcite.rel.core.Sort

All Implemented Interfaces:

Cloneable, RelOptNode, Hintable, RelNode

Direct Known Subclasses:

Bindables.BindableSort, EnumerableLimitSort, EnumerableSort, JdbcRules.JdbcSort, LogicalSort

public abstract class Sort
extends SingleRel
implements Hintable

Relational expression that imposes a particular sort order on its input without otherwise changing its content.

Nested Class Summary

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

RelNode.Context

Field Summary

Fields

Modifier and Type	Field and Description
RelCollation	collation
@Nullable RexNode	fetch
protected com.google.common.collect.ImmutableList<RelHint>	hints
@Nullable RexNode	offset

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 and Description
protected	Sort(RelInput input) Creates a Sort by parsing serialized output.
protected	Sort(RelOptCluster cluster, RelTraitSet traits, List<RelHint> hints, RelNode child, RelCollation collation, @Nullable RexNode offset, @Nullable RexNode fetch) Creates a Sort.
protected	Sort(RelOptCluster cluster, RelTraitSet traits, RelNode child, RelCollation collation) Creates a Sort.
protected	Sort(RelOptCluster cluster, RelTraitSet traits, RelNode child, RelCollation collation, @Nullable RexNode offset, @Nullable RexNode fetch) Creates a Sort.

Method Summary

Modifier and Type	Method and Description
RelNode	accept(RexShuttle shuttle) Accepts a visit from a shuttle.
@Nullable RelOptCost	computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) Returns the cost of this plan (not including children).
Sort	copy(RelTraitSet traitSet, List<RelNode> inputs) Creates a copy of this relational expression, perhaps changing traits and inputs.
Sort	copy(RelTraitSet traitSet, RelNode newInput, RelCollation newCollation)
abstract Sort	copy(RelTraitSet traitSet, RelNode newInput, RelCollation newCollation, @Nullable RexNode offset, @Nullable RexNode fetch)
RelWriter	explainTerms(RelWriter pw) Describes the inputs and attributes of this relational expression.
RelCollation	getCollation() Returns the array of RelFieldCollations asked for by the sort specification, from most significant to least significant.
com.google.common.collect.ImmutableList<RelHint>	getHints() Returns the hints of this relational expressions as an immutable list.
List<RexNode>	getSortExps() Returns the sort expressions.
boolean	isEnforcer() Indicates whether it is an enforcer operator, e.g.

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, deepEquals, deepHashCode, equals, explain, getCluster, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getRelDigest, getRelTypeName, getRowType, getTable, getTraitSet, getVariablesSet, hashCode, isValid, metadata, onRegister, recomputeDigest, register, sole, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.calcite.rel.hint.Hintable

attachHints, withHints

Methods inherited from interface org.apache.calcite.rel.RelNode

explain, fieldIsNullable

Field Detail

collation

public final RelCollation collation

offset

public final @Nullable RexNode offset

fetch

public final @Nullable RexNode fetch

hints

protected final com.google.common.collect.ImmutableList<RelHint> hints

Constructor Detail

Sort

protected Sort(RelOptCluster cluster,
               RelTraitSet traits,
               List<RelHint> hints,
               RelNode child,
               RelCollation collation,
               @Nullable RexNode offset,
               @Nullable RexNode fetch)

Creates a Sort.

Parameters:

cluster - Cluster this relational expression belongs to

traits - Traits

hints - Hints for this node

child - input relational expression

collation - array of sort specifications

offset - Expression for number of rows to discard before returning first row

fetch - Expression for number of rows to fetch

Sort

protected Sort(RelOptCluster cluster,
               RelTraitSet traits,
               RelNode child,
               RelCollation collation)

Creates a Sort.

Parameters:

cluster - Cluster this relational expression belongs to

traits - Traits

child - input relational expression

collation - array of sort specifications

Sort

protected Sort(RelOptCluster cluster,
               RelTraitSet traits,
               RelNode child,
               RelCollation collation,
               @Nullable RexNode offset,
               @Nullable RexNode fetch)

Creates a Sort.

Parameters:

cluster - Cluster this relational expression belongs to

traits - Traits

child - input relational expression

collation - array of sort specifications

offset - Expression for number of rows to discard before returning first row

fetch - Expression for number of rows to fetch

Sort

protected Sort(RelInput input)

Creates a Sort by parsing serialized output.

Method Detail

copy

public final Sort copy(RelTraitSet traitSet,
                       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 final Sort copy(RelTraitSet traitSet,
                       RelNode newInput,
                       RelCollation newCollation)

copy

public abstract Sort copy(RelTraitSet traitSet,
                          RelNode newInput,
                          RelCollation newCollation,
                          @Nullable RexNode offset,
                          @Nullable RexNode fetch)

computeSelfCost

public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
                                            RelMetadataQuery mq)

Returns the cost of this plan (not including children). The base implementation throws an error; derived classes should override.

NOTE jvs 29-Mar-2006: Don't call this method directly. Instead, use RelMetadataQuery.getNonCumulativeCost(org.apache.calcite.rel.RelNode), which gives plugins a chance to override the rel's default ideas about cost.

The CPU cost of a Sort has three main cases:

• If fetch is zero, CPU cost is zero; otherwise,
• if the sort keys are empty, we don't need to sort, only step over the rows, and therefore the CPU cost is min(fetch + offset, inputRowCount) * bytesPerRow; otherwise
• we need to read and sort inputRowCount rows, with at most min(fetch + offset, inputRowCount) of them in the sort data structure at a time, giving a CPU cost of inputRowCount * log(min(fetch + offset, inputRowCount)) * bytesPerRow.

The cost model factors in row width via bytesPerRow, because sorts need to move rows around, not just compare them; by making the cost higher if rows are wider, we discourage pushing a Project through a Sort. We assume that each field is 4 bytes, and we add 3 'virtual fields' to represent the per-row overhead. Thus a 1-field row is (3 + 1) * 4 = 16 bytes; a 5-field row is (3 + 5) * 4 = 32 bytes.

The cost model does not consider a 5-field sort to be more expensive than, say, a 2-field sort, because both sorts will compare just one field most of the time.

Specified by:

computeSelfCost in interface RelNode

Overrides:

computeSelfCost in class AbstractRelNode

Parameters:

planner - Planner for cost calculation

mq - Metadata query

Returns:

Cost of this plan (not including children)

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

isEnforcer

public boolean isEnforcer()

Description copied from interface: RelNode

Indicates whether it is an enforcer operator, e.g. PhysicalSort, PhysicalHashDistribute, etc. As an enforcer, the operator must be created only when required traitSet is not satisfied by its input.

Specified by:

isEnforcer in interface RelNode

Overrides:

isEnforcer in class AbstractRelNode

Returns:

Whether it is an enforcer operator

getCollation

public RelCollation getCollation()

Returns the array of RelFieldCollations asked for by the sort specification, from most significant to least significant.

See also RelMetadataQuery.collations(RelNode), which lists all known collations. For example, ORDER BY time_id might also be sorted by the_year, the_month because of a known monotonicity constraint among the columns. getCollation would return [time_id] and collations would return [ [time_id], [the_year, the_month] ].

getSortExps

public List<RexNode> getSortExps()

Returns the sort expressions.

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 RelWriter.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

getHints

public com.google.common.collect.ImmutableList<RelHint> getHints()

Description copied from interface: Hintable

Returns the hints of this relational expressions as an immutable list.

Specified by:

getHints in interface Hintable