Package org.apache.calcite.rel

Class RelRoot

java.lang.Object

org.apache.calcite.rel.RelRoot

public class RelRoot
extends java.lang.Object

Root of a tree of RelNode.

One important reason that RelRoot exists is to deal with queries like

SELECT name FROM emp ORDER BY empno DESC

Calcite knows that the result must be sorted, but cannot represent its sort order as a collation, because empno is not a field in the result.

Instead we represent this as

RelRoot: { rel: Sort($1 DESC) Project(name, empno) TableScan(EMP) fields: [0] collation: [1 DESC] }

Note that the empno field is present in the result, but the fields mask tells the consumer to throw it away.

Another use case is queries like this:

SELECT name AS n, name AS n2, empno AS n FROM emp

The there are multiple uses of the name field. and there are multiple columns aliased as n. You can represent this as

RelRoot: { rel: Project(name, empno) TableScan(EMP) fields: [(0, "n"), (0, "n2"), (1, "n")] collation: [] }

Field Summary

Fields

Modifier and Type	Field	Description
RelCollation	collation
com.google.common.collect.ImmutableList<Pair<java.lang.Integer,java.lang.String>>	fields
SqlKind	kind
RelNode	rel
RelDataType	validatedRowType

Constructor Summary

Constructors

Constructor	Description
RelRoot(RelNode rel, RelDataType validatedRowType, SqlKind kind, java.util.List<Pair<java.lang.Integer,java.lang.String>> fields, RelCollation collation)	Creates a RelRoot.

Method Summary

Modifier and Type	Method	Description
boolean	isCollationTrivial()
boolean	isNameTrivial()
boolean	isRefTrivial()
static RelRoot	of(RelNode rel, RelDataType rowType, SqlKind kind)	Creates a simple RelRoot.
static RelRoot	of(RelNode rel, SqlKind kind)	Creates a simple RelRoot.
RelNode	project()	Returns the root relational expression, creating a LogicalProject if necessary to remove fields that are not needed.
RelNode	project(boolean force)	Returns the root relational expression as a LogicalProject.
java.lang.String	toString()
RelRoot	withCollation(RelCollation collation)
RelRoot	withKind(SqlKind kind)	Creates a copy, assigning a new kind.
RelRoot	withRel(RelNode rel)	Creates a copy of this RelRoot, assigning a RelNode.

Methods inherited from class java.lang.Object

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

Field Detail

rel

public final RelNode rel

validatedRowType

public final RelDataType validatedRowType

kind

public final SqlKind kind

fields

public final com.google.common.collect.ImmutableList<Pair<java.lang.Integer,java.lang.String>> fields

collation

public final RelCollation collation

Constructor Detail

RelRoot

public RelRoot(RelNode rel,
               RelDataType validatedRowType,
               SqlKind kind,
               java.util.List<Pair<java.lang.Integer,java.lang.String>> fields,
               RelCollation collation)

Creates a RelRoot.

Parameters:

validatedRowType - Original row type returned by query validator

kind - Type of query (SELECT, UPDATE, ...)

Method Detail

of

public static RelRoot of(RelNode rel,
                         SqlKind kind)

Creates a simple RelRoot.

of

public static RelRoot of(RelNode rel,
                         RelDataType rowType,
                         SqlKind kind)

Creates a simple RelRoot.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

withRel

public RelRoot withRel(RelNode rel)

Creates a copy of this RelRoot, assigning a RelNode.

withKind

public RelRoot withKind(SqlKind kind)

Creates a copy, assigning a new kind.

withCollation

public RelRoot withCollation(RelCollation collation)

project

public RelNode project()

Returns the root relational expression, creating a LogicalProject if necessary to remove fields that are not needed.

project

public RelNode project(boolean force)

Returns the root relational expression as a LogicalProject.

Parameters:

force - Create a Project even if all fields are used

isNameTrivial

public boolean isNameTrivial()

isRefTrivial

public boolean isRefTrivial()

isCollationTrivial

public boolean isCollationTrivial()