org.eigenbase.rel
Class ProjectRel

java.lang.Object
  org.eigenbase.rel.AbstractRelNode
      org.eigenbase.rel.SingleRel
          org.eigenbase.rel.ProjectRelBase
              org.eigenbase.rel.ProjectRel

All Implemented Interfaces:

Cloneable, RelNode

public final class ProjectRel
extends ProjectRelBase

ProjectRel is a relational expression which computes a set of 'select expressions' from its input relational expression.

The result is usually 'boxed' as a record with one named field for each column; if there is precisely one expression, the result may be 'unboxed', and consist of the raw value type.

Since:

March, 2004

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rel/ProjectRel.java#18 $

Author:

jhyde

Nested Class Summary

Nested classes/interfaces inherited from class org.eigenbase.rel.ProjectRelBase

ProjectRelBase.Flags

Field Summary

Fields inherited from class org.eigenbase.rel.ProjectRelBase

exps, flags

Fields inherited from class org.eigenbase.rel.AbstractRelNode

digest, id, nextId, rowType, traits

Fields inherited from interface org.eigenbase.rel.RelNode

emptyArray

Constructor Summary

ProjectRel(RelOptCluster cluster, RelNode child, RexNode[] exps, RelDataType rowType, int flags, List<RelCollation> collationList)
Creates a ProjectRel.

ProjectRel(RelOptCluster cluster, RelNode child, RexNode[] exps, String[] fieldNames, int flags)
Creates a ProjectRel with no sort keys.

Method Summary

ProjectRel	clone() Clones this RelNode.
Permutation	getPermutation() Returns a permutation, if this projection is merely a permutation of its input fields, otherwise null.

Methods inherited from class org.eigenbase.rel.ProjectRelBase

computeSelfCost, explain, getChildExps, getCollationList, getFlags, getProjectExps, implementFieldAccess, isBoxed, isValid

Methods inherited from class org.eigenbase.rel.SingleRel

childrenAccept, deriveRowType, getChild, getInputs, getRows, replaceInput

Methods inherited from class org.eigenbase.rel.AbstractRelNode

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

Methods inherited from class java.lang.Object

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

Constructor Detail

ProjectRel

public ProjectRel(RelOptCluster cluster,
                  RelNode child,
                  RexNode[] exps,
                  String[] fieldNames,
                  int flags)

Creates a ProjectRel with no sort keys.

Parameters:

cluster - Cluster this relational expression belongs to

child - input relational expression

exps - set of expressions for the input columns

fieldNames - aliases of the expressions

flags - values as in ProjectRelBase.Flags

ProjectRel

public ProjectRel(RelOptCluster cluster,
                  RelNode child,
                  RexNode[] exps,
                  RelDataType rowType,
                  int flags,
                  List<RelCollation> collationList)

Creates a ProjectRel.

Parameters:

cluster - Cluster this relational expression belongs to

child - input relational expression

exps - set of expressions for the input columns

rowType - output row type

flags - values as in ProjectRelBase.Flags

collationList - List of sort keys

Method Detail

clone

public ProjectRel 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

Specified by:

clone in class AbstractRelNode

Returns:

a clone of this RelNode

getPermutation

public Permutation getPermutation()

Returns a permutation, if this projection is merely a permutation of its input fields, otherwise null.