org.apache.drill.exec.physical.resultSet.project

Class RequestedTupleImpl

java.lang.Object

org.apache.drill.exec.physical.resultSet.project.RequestedTupleImpl

All Implemented Interfaces:

RequestedTuple

public class RequestedTupleImpl
extends Object
implements RequestedTuple

Represents an explicit projection at some tuple level. A tuple is the top-level row or a map.

A column is projected if it is explicitly listed in the selection list.

If a column is a map, then the projection for the map's columns is based on two rules:

1. If the projection list includes at least one explicit mention of a map member, then include only those columns explicitly listed.
2. If the projection at the parent level lists only the map column itself (which the projection can't know is a map), then assume this implies all columns, as if the entry where "map.*".

Examples:
m
If m turns out to be a map, project all members of m.
m.a
Column m must be a map. Project only column a.
m, m.a
Tricky case. We interpret this as projecting only the "a" element of map m.

The projection set is built from a list of columns, represented as SchemaPath objects, provided by the physical plan. The structure of SchemaPath is a bit awkward:

• SchemaPath> is a wrapper for a column which directly holds the NameSegment for the top-level column.
• NameSegment holds a name. This can be a top name such as `a`, or parts of a compound name such as `a`.`b`. Each NameSegment has a "child" that points to the option following parts of the name.
• is the base class for the parts of a name.
• ArraySegment is the other kind of name part and represents an array index such as the "[1]" in `columns`[1].
The parser considers names and array indexes. Example:

 a
 a.b
 a[2]
 a[2].b
 a[1][2][3]
 a[1][2][3].b.c
 a['foo'][0].b['bar']
 

Usage

The projection information is a pattern which supports queries of the form "is this column projected", and "if projected, is the projection consistent with such-and-so concrete type?" Clients should not try to work out the meaning of the pattern: doing so is very complex. Instead, do the following:

 String colName = ...;
 ColumnMetadata colDef = ...;
 InputTupleProjection tupleProj = ...
 if (tupleProj.isProjected(colName)) {
   if (!tupleProj.isComsistentWith(colDef)) {
     // Raise an error
   }
   // Handle a projected column.
 }

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.drill.exec.physical.resultSet.project.RequestedTuple

RequestedTuple.TupleProjectionType

Field Summary

Fields

Modifier and Type	Field and Description
protected RequestedTuple.TupleProjectionType	projectionType

Constructor Summary

Constructors

Constructor and Description
RequestedTupleImpl()
RequestedTupleImpl(List<RequestedColumn> cols)
RequestedTupleImpl(RequestedColumnImpl parent)

Method Summary

Modifier and Type	Method and Description
void	buildName(StringBuilder buf)
boolean	enforceProjection(ColumnMetadata columnSchema, CustomErrorContext errorContext)
RequestedColumn	get(int i)
RequestedColumn	get(String colName)
protected RequestedColumnImpl	getImpl(String colName)
boolean	isEmpty() Report if the projection is empty as occurs in SELECT COUNT(*) FROM ....
boolean	isProjected(ColumnMetadata columnSchema)
boolean	isProjected(String colName)
RequestedTuple	mapProjection(String colName)
protected RequestedColumn	project(String colName)
List<RequestedColumn>	projections()
int	size()
String	toString()
RequestedTuple.TupleProjectionType	type() Tuple projection type.

Methods inherited from class java.lang.Object

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

Field Detail

projectionType

protected RequestedTuple.TupleProjectionType projectionType

Constructor Detail

RequestedTupleImpl

public RequestedTupleImpl()

RequestedTupleImpl

public RequestedTupleImpl(RequestedColumnImpl parent)

RequestedTupleImpl

public RequestedTupleImpl(List<RequestedColumn> cols)

Method Detail

size

public int size()

Specified by:

size in interface RequestedTuple

get

public RequestedColumn get(int i)

Specified by:

get in interface RequestedTuple

get

public RequestedColumn get(String colName)

Specified by:

get in interface RequestedTuple

getImpl

protected RequestedColumnImpl getImpl(String colName)

project

protected RequestedColumn project(String colName)

projections

public List<RequestedColumn> projections()

Specified by:

projections in interface RequestedTuple

buildName

public void buildName(StringBuilder buf)

Specified by:

buildName in interface RequestedTuple

type

public RequestedTuple.TupleProjectionType type()

Tuple projection type. This is a rough approximation. A scan-level projection may include both a wildcard and implicit columns. This form is best used in testing where such ambiguities do not apply.

Specified by:

type in interface RequestedTuple

isProjected

public boolean isProjected(String colName)

Specified by:

isProjected in interface RequestedTuple

isProjected

public boolean isProjected(ColumnMetadata columnSchema)

Specified by:

isProjected in interface RequestedTuple

enforceProjection

public boolean enforceProjection(ColumnMetadata columnSchema,
                                 CustomErrorContext errorContext)

Specified by:

enforceProjection in interface RequestedTuple

mapProjection

public RequestedTuple mapProjection(String colName)

Specified by:

mapProjection in interface RequestedTuple

toString

public String toString()

Overrides:

toString in class Object

isEmpty

public boolean isEmpty()

Description copied from interface: RequestedTuple

Report if the projection is empty as occurs in SELECT COUNT(*) FROM .... This is not the same as asking if this tuple is unprojected, as that concept does not apply to tuples, only to the column that contains the tuple.

Specified by:

isEmpty in interface RequestedTuple

Returns:

true if the projection set is empty