net.sf.farrago.fennel.rel
Class FennelMultiUseBufferRel

java.lang.Object
  org.eigenbase.rel.AbstractRelNode
      org.eigenbase.rel.SingleRel
          net.sf.farrago.fennel.rel.FennelSingleRel
              net.sf.farrago.fennel.rel.FennelBufferRel
                  net.sf.farrago.fennel.rel.FennelMultiUseBufferRel

All Implemented Interfaces:

Cloneable, FennelRel, RelNode

public class FennelMultiUseBufferRel
extends FennelBufferRel

FennelMultiUseBufferRel represents the Fennel implementation of a buffering stream that's used in multiple places in a stream graph.

Within the query tree, a single instance of this object can be referenced multiple times. Each reference corresponds to a node that needs to read the same buffered data. When converting this object to a streamDef, each reference to the object will result in the creation of a buffer reader stream. In addition, a single buffer writer stream is created that will be "shared" by the buffer readers. Hence, there will be one buffer writer stream and one or more buffer reader streams per FennelMultiUseBufferRel object.

The writer stream will have an incoming input stream corresponding to the input into the FennelMultiUseBufferRel. Dataflows will be created from the writer stream to its corresponding reader streams. That dataflow will be used by the writer stream to communicate to the readers the first pageId of the buffered data.

The writer and reader streams will also share a dynamic parameter that will be used to keep track of the number of active readers.

Note that unlike FennelBufferRel, FennelMultiUseBufferRel only supports "multipass = true" semantics. The parameter cannot be set to false, even if the buffered contents are only going to be used once.

Version:

$Id: //open/dev/farrago/src/net/sf/farrago/fennel/rel/FennelMultiUseBufferRel.java#1 $

Author:

Zelaine Fong

Field Summary

private FennelRelParamId

readerRefCountParamId Id of the dynamic parameter that the writer will use to keep track of the number of active readers.

Fields inherited from class net.sf.farrago.fennel.rel.FennelBufferRel

inMemory, multiPass

Fields inherited from class org.eigenbase.rel.AbstractRelNode

digest, id, rowType, traits

Fields inherited from interface net.sf.farrago.query.FennelRel

FENNEL_EXEC_CONVENTION

Fields inherited from interface org.eigenbase.rel.RelNode

emptyArray

Constructor Summary

FennelMultiUseBufferRel(RelOptCluster cluster, RelNode child, boolean inMemory)
Creates a new FennelMultiUseBufferRel object.

Method Summary

FennelMultiUseBufferRel	clone() Clones this RelNode.
void	explain(RelOptPlanWriter pw)
Object	implementFennelChild(FennelRelImplementor implementor) Visits this relational expression as part of the implementation process.
FemExecutionStreamDef	toStreamDef(FennelRelImplementor implementor) Converts this relational expression to FemExecutionStreamDef form.

Methods inherited from class net.sf.farrago.fennel.rel.FennelBufferRel

computeSelfCost, getRows, isInMemory

Methods inherited from class net.sf.farrago.fennel.rel.FennelSingleRel

getCollations, getFarragoTypeFactory

Methods inherited from class org.eigenbase.rel.SingleRel

childrenAccept, deriveRowType, getChild, getInputs, replaceInput

Methods inherited from class org.eigenbase.rel.AbstractRelNode

cloneTraits, collectVariablesSet, collectVariablesUsed, computeDigest, getChildExps, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getOrCreateCorrelVariable, getQuery, getRelTypeName, getRowType, getTable, getTraits, getVariablesStopped, inheritTraitsFrom, isAccessTo, isDistinct, isValid, onRegister, recomputeDigest, register, registerCorrelVariable, setCorrelVariable, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eigenbase.rel.RelNode

childrenAccept, collectVariablesSet, collectVariablesUsed, getChildExps, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getInputs, getOrCreateCorrelVariable, getQuery, getRelTypeName, getRowType, getTable, getTraits, getVariablesStopped, isAccessTo, isDistinct, isValid, onRegister, recomputeDigest, registerCorrelVariable, replaceInput, setCorrelVariable

Field Detail

readerRefCountParamId

private FennelRelParamId readerRefCountParamId

Id of the dynamic parameter that the writer will use to keep track of the number of active readers.

Constructor Detail

FennelMultiUseBufferRel

public FennelMultiUseBufferRel(RelOptCluster cluster,
                               RelNode child,
                               boolean inMemory)

Creates a new FennelMultiUseBufferRel object.

Parameters:

cluster - RelOptCluster for this rel

child - child input

inMemory - true if the buffering needs to be done only in memory by a single instance of a stream

Method Detail

clone

public FennelMultiUseBufferRel clone()

Description copied from interface: RelNode

Clones this RelNode.

Traits of the RelNode must be explicitly cloned, using AbstractRelNode.inheritTraitsFrom(AbstractRelNode), as the RelNode may have traits of which it has no knowledge. Example implementation:

     public MyRelNode clone()
     {
         MyRelNode clone = new MyRelNode(...);
         clone.inheritTraitsFrom(this);
         return clone;
     }
 

N.B.: This method must be overridden whenever an existing, concrete RelNode is extended. Otherwise, calling clone() will produce a differently typed RelNode, resulting in invalid or incorrect query plans.

Specified by:

clone in interface RelNode

Overrides:

clone in class FennelBufferRel

Returns:

a clone of this RelNode

explain

public void explain(RelOptPlanWriter pw)

Specified by:

explain in interface RelNode

Overrides:

explain in class FennelBufferRel

toStreamDef

public FemExecutionStreamDef toStreamDef(FennelRelImplementor implementor)

Description copied from interface: FennelRel

Converts this relational expression to FemExecutionStreamDef form. In the process, the relational expression will almost certainly call FennelRelImplementor.visitFennelChild(net.sf.farrago.query.FennelRel, int) on each of its children.

Specified by:

toStreamDef in interface FennelRel

Overrides:

toStreamDef in class FennelBufferRel

Parameters:

implementor - for generating Java code

Returns:

generated FemExecutionStreamDef

implementFennelChild

public Object implementFennelChild(FennelRelImplementor implementor)

Description copied from interface: FennelRel

Visits this relational expression as part of the implementation process. Fennel relational expressions are implemented in a two-phase process: first call this method, then call FennelRel.toStreamDef(net.sf.farrago.query.FennelRelImplementor).

Specified by:

implementFennelChild in interface FennelRel

Overrides:

implementFennelChild in class FennelSingleRel