Package org.apache.calcite.adapter.cassandra

Class CassandraSort

java.lang.Object

org.apache.calcite.rel.AbstractRelNode

org.apache.calcite.rel.SingleRel

org.apache.calcite.rel.core.Sort

org.apache.calcite.adapter.cassandra.CassandraSort

All Implemented Interfaces:

Cloneable, CassandraRel, RelOptNode, Hintable, RelNode

public class CassandraSort
extends Sort
implements CassandraRel

Implementation of Sort relational expression in Cassandra.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.calcite.adapter.cassandra.CassandraRel

CassandraRel.Implementor

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

RelNode.Context

Field Summary

Fields inherited from class org.apache.calcite.rel.core.Sort

collation, fetch, hints, offset

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

input

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

digest, id, rowType, traitSet

Fields inherited from interface org.apache.calcite.adapter.cassandra.CassandraRel

CONVENTION

Constructor Summary

Constructors

Constructor	Description
CassandraSort(RelOptCluster cluster, RelTraitSet traitSet, RelNode child, RelCollation collation)

Method Summary

Modifier and Type	Method	Description
@Nullable RelOptCost	computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq)	Returns the cost of this plan (not including children).
Sort	copy(RelTraitSet traitSet, RelNode input, RelCollation newCollation, @Nullable RexNode offset, @Nullable RexNode fetch)
void	implement(CassandraRel.Implementor implementor)

Methods inherited from class org.apache.calcite.rel.core.Sort

accept, copy, copy, explainTerms, getCollation, getHints, getSortExps, isEnforcer

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

accept, accept, childrenAccept, collectVariablesSet, collectVariablesUsed, copy, deepEquals, deepHashCode, estimateRowCount, explain, explain, fieldIsNullable, getConvention, getCorrelVariable, getDigest, getExpectedInputRowType, getInput, getInputs, getRelDigest, getRelTypeName, getRowType, getTable, getVariablesSet, isEnforcer, isValid, metadata, onRegister, recomputeDigest, register, replaceInput, stripped

Methods inherited from interface org.apache.calcite.plan.RelOptNode

getCluster, getDescription, getId, getTraitSet

Constructor Details

CassandraSort

public CassandraSort(RelOptCluster cluster,
 RelTraitSet traitSet,
 RelNode child,
 RelCollation collation)

Method Details

computeSelfCost

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

Description copied from class: Sort

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 Sort

Parameters:

planner - Planner for cost calculation

mq - Metadata query

Returns:

Cost of this plan (not including children)

copy

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

Specified by:

copy in class Sort

implement

public void implement(CassandraRel.Implementor implementor)

Specified by:

implement in interface CassandraRel