org.apache.beam.sdk.extensions.sql.impl.rel

Class BeamSortRel

java.lang.Object

Sort

org.apache.beam.sdk.extensions.sql.impl.rel.BeamSortRel

All Implemented Interfaces:

BeamRelNode

public class BeamSortRel
extends Sort
implements BeamRelNode

BeamRelNode to replace a Sort node.

Since Beam does not fully supported global sort we are using Top to implement the Sort algebra. The following types of ORDER BY are supported:

     select * from t order by id desc limit 10;
     select * from t order by id desc limit 10 offset 5;
 

but Order BY without a limit is NOT supported:

   select * from t order by id desc
 

Constraints

• Due to the constraints of Top, the result of a `ORDER BY LIMIT` must fit into the memory of a single machine.
• Since `WINDOW`(HOP, TUMBLE, SESSION etc) is always associated with `GroupBy`, it does not make much sense to use `ORDER BY` with `WINDOW`.

Constructor Summary

Constructors

Constructor and Description
BeamSortRel(RelOptCluster cluster, RelTraitSet traits, RelNode child, RelCollation collation, RexNode offset, RexNode fetch)

Method Summary

Modifier and Type	Method and Description
PCollection<BeamRecord>	buildBeamPipeline(PCollectionTuple inputPCollections, BeamSqlEnv sqlEnv) A BeamRelNode is a recursive structure, the BeamQueryPlanner visits it with a DFS(Depth-First-Search) algorithm.
Sort	copy(RelTraitSet traitSet, RelNode newInput, RelCollation newCollation, RexNode offset, RexNode fetch)

Methods inherited from class java.lang.Object

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

Constructor Detail

BeamSortRel

public BeamSortRel(RelOptCluster cluster,
                   RelTraitSet traits,
                   RelNode child,
                   RelCollation collation,
                   RexNode offset,
                   RexNode fetch)

Method Detail

buildBeamPipeline

public PCollection<BeamRecord> buildBeamPipeline(PCollectionTuple inputPCollections,
                                                 BeamSqlEnv sqlEnv)
                                          throws java.lang.Exception

Description copied from interface: BeamRelNode

A BeamRelNode is a recursive structure, the BeamQueryPlanner visits it with a DFS(Depth-First-Search) algorithm.

Specified by:

buildBeamPipeline in interface BeamRelNode

Throws:

java.lang.Exception

copy

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