org.apache.pig.impl.logicalLayer.schema

Class Schema.FieldSchema

java.lang.Object

org.apache.pig.impl.logicalLayer.schema.Schema.FieldSchema

All Implemented Interfaces:

Serializable, Cloneable

Enclosing class:

Schema

public static class Schema.FieldSchema
extends Object
implements Serializable, Cloneable

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
String	alias Alias for this field.
String	canonicalName Canonical name.
static CanonicalNamer	canonicalNamer Canonical namer object to generate new canonical names on request.
Schema	schema If this is a tuple itself, it can have a schema.
byte	type Datatype, using codes from DataType.

Constructor Summary

Constructors

Constructor and Description
FieldSchema(Schema.FieldSchema fs) Copy Constructor.
FieldSchema(String a, byte t) Constructor for any type.
FieldSchema(String a, Schema s) Constructor for tuple fields.
FieldSchema(String a, Schema s, byte t) Constructor for tuple fields.

Method Summary

Modifier and Type	Method and Description
static boolean	castable(Schema.FieldSchema castFs, Schema.FieldSchema inputFs) Recursively compare two schemas to check if the input schema can be cast to the cast schema
Schema.FieldSchema	clone() Make a deep copy of this FieldSchema and return it.
boolean	equals(Object other) Two field schemas are equal if types and schemas are equal in all levels.
static boolean	equals(Schema.FieldSchema fschema, Schema.FieldSchema fother, boolean relaxInner, boolean relaxAlias) Compare two field schema for equality
Schema.FieldSchema	findFieldSchema(String canonicalName) Find a field schema instance in this FieldSchema hierarchy (including "this") that matches the given canonical name.
int	hashCode()
Schema.FieldSchema	mergePrefixFieldSchema(Schema.FieldSchema otherFs) Recursively prefix merge two schemas
Schema.FieldSchema	mergePrefixFieldSchema(Schema.FieldSchema otherFs, boolean otherTakesAliasPrecedence) Recursively prefix merge two schemas
Schema.FieldSchema	mergePrefixFieldSchema(Schema.FieldSchema otherFs, boolean otherTakesAliasPrecedence, boolean allowMergeableTypes) Recursively prefix merge two schemas
static void	setFieldSchemaDefaultType(Schema.FieldSchema fs, byte t) Recursively set NULL type to the specifid type
String	toString()

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

alias

public String alias

Alias for this field.

type

public byte type

Datatype, using codes from DataType.

schema

public Schema schema

If this is a tuple itself, it can have a schema. Otherwise this field must be null.

canonicalName

public String canonicalName

Canonical name. This name uniquely identifies a field throughout the query. Unlike a an alias, it cannot be changed. It will change when the field is transformed in some way (such as being used in an arithmetic expression or passed to a udf). At that point a new canonical name will be generated for the field.

canonicalNamer

public static final CanonicalNamer canonicalNamer

Canonical namer object to generate new canonical names on request. In order to ensure unique and consistent names, across all field schema objects, the object is made static.

Constructor Detail

FieldSchema

public FieldSchema(String a,
                   byte t)

Constructor for any type.

Parameters:

a - Alias, if known. If unknown leave null.

t - Type, using codes from DataType.

FieldSchema

public FieldSchema(String a,
                   Schema s)

Constructor for tuple fields.

Parameters:

a - Alias, if known. If unknown leave null.

s - Schema of this tuple.

FieldSchema

public FieldSchema(String a,
                   Schema s,
                   byte t)
            throws FrontendException

Constructor for tuple fields.

Parameters:

a - Alias, if known. If unknown leave null.

s - Schema of this tuple.

t - Type, using codes from DataType.

Throws:

FrontendException

FieldSchema

public FieldSchema(Schema.FieldSchema fs)

Copy Constructor.

Parameters:

fs - Source FieldSchema

Method Detail

equals

public boolean equals(Object other)

Two field schemas are equal if types and schemas are equal in all levels. In order to relax alias equivalent requirement, instead use equals(FieldSchema fschema, FieldSchema fother, boolean relaxInner, boolean relaxAlias)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

castable

public static boolean castable(Schema.FieldSchema castFs,
                               Schema.FieldSchema inputFs)

Recursively compare two schemas to check if the input schema can be cast to the cast schema

Parameters:

castFs - schema of the cast operator

inputFs - schema of the cast input

Returns:

true or falsew!

equals

public static boolean equals(Schema.FieldSchema fschema,
                             Schema.FieldSchema fother,
                             boolean relaxInner,
                             boolean relaxAlias)

Compare two field schema for equality

Parameters:

fschema -

fother -

relaxInner - If true, we don't check inner tuple schemas

relaxAlias - If true, we don't check aliases

Returns:

true if FieldSchemas are equal, false otherwise

toString

public String toString()

Overrides:

toString in class Object

clone

public Schema.FieldSchema clone()
                         throws CloneNotSupportedException

Make a deep copy of this FieldSchema and return it.

Overrides:

clone in class Object

Returns:

clone of the this FieldSchema.

Throws:

CloneNotSupportedException

mergePrefixFieldSchema

public Schema.FieldSchema mergePrefixFieldSchema(Schema.FieldSchema otherFs)
                                          throws SchemaMergeException

Recursively prefix merge two schemas

Parameters:

otherFs - the other field schema to be merged with

Returns:

the prefix merged field schema this can be null if one schema is null and allowIncompatibleTypes is true

Throws:

SchemaMergeException - if they cannot be merged

mergePrefixFieldSchema

public Schema.FieldSchema mergePrefixFieldSchema(Schema.FieldSchema otherFs,
                                                 boolean otherTakesAliasPrecedence)
                                          throws SchemaMergeException

Recursively prefix merge two schemas

Parameters:

otherFs - the other field schema to be merged with

otherTakesAliasPrecedence - true if aliases from the other field schema take precedence

Returns:

the prefix merged field schema this can be null if one schema is null and allowIncompatibleTypes is true

Throws:

SchemaMergeException - if they cannot be merged

mergePrefixFieldSchema

public Schema.FieldSchema mergePrefixFieldSchema(Schema.FieldSchema otherFs,
                                                 boolean otherTakesAliasPrecedence,
                                                 boolean allowMergeableTypes)
                                          throws SchemaMergeException

Recursively prefix merge two schemas

Parameters:

otherFs - the other field schema to be merged with

otherTakesAliasPrecedence - true if aliases from the other field schema take precedence

allowMergeableTypes - true if "mergeable" types should be allowed. Two types are mergeable if any of the following conditions is true IN THE BELOW ORDER of checks: 1) if either one has a type null or unknown and other has a type OTHER THAN null or unknown, the result type will be the latter non null/unknown type 2) If either type is bytearray, then result type will be the other (possibly non BYTEARRAY) type 3) If current type can be cast to the other type, then the result type will be the other type

Returns:

the prefix merged field schema this can be null.

Throws:

SchemaMergeException - if they cannot be merged

setFieldSchemaDefaultType

public static void setFieldSchemaDefaultType(Schema.FieldSchema fs,
                                             byte t)

Recursively set NULL type to the specifid type

Parameters:

fs - the field schema whose NULL type has to be set

t - the specified type

findFieldSchema

public Schema.FieldSchema findFieldSchema(String canonicalName)

Find a field schema instance in this FieldSchema hierarchy (including "this") that matches the given canonical name.

Parameters:

canonicalName - canonical name

Returns:

the FieldSchema instance found