org.apache.hadoop.zebra.schema

Class Schema

java.lang.Object

org.apache.hadoop.zebra.schema.Schema

All Implemented Interfaces:

Comparable<Schema>, org.apache.hadoop.io.Writable

public class Schema
extends Object
implements Comparable<Schema>, org.apache.hadoop.io.Writable

Logical schema of tabular data.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Schema.ColumnSchema Column Schema in Schema
static class	Schema.ParsedName Helper class to parse a column name string one section at a time and find the required type for the parsed part.

Field Summary

Fields

Modifier and Type	Field and Description
static String	COLUMN_DELIMITER

Constructor Summary

Constructors

Constructor and Description
Schema() Constructor - schema for empty schema (zero-column) .
Schema(boolean projection) Constructor - schema for empty projection/schema (zero-column) .
Schema(Schema.ColumnSchema fs)
Schema(String schema) Constructor - create a schema from a string representation.
Schema(String[] columns) Constructor - create a schema from an array of column names.
Schema(String schema, boolean projection)

Method Summary

Methods

Modifier and Type	Method and Description
void	add(Schema.ColumnSchema f) add a column
int	compareTo(Schema other)
boolean	equals(Object obj)
Schema.ColumnSchema	getColumn(int index) Get a particular column's schema
Schema.ColumnSchema	getColumn(String name) get a column by name
int	getColumnIndex(String name) Get the index of the column for the input column name.
String	getColumnName(int index)
String[]	getColumns() Get the names of the individual columns.
Schema.ColumnSchema	getColumnSchema(Schema.ParsedName pn) find the most fitting subcolumn containing the name: the parsed name is set after the field name plus any possible separator of '.' or '#'.
Schema.ColumnSchema	getColumnSchema(String name) Get a column's schema
Schema.ColumnSchema	getColumnSchemaOnParsedName(Schema.ParsedName pn) Get a subcolumn's schema and move the name just parsed into the next subtype
int	getNumColumns() Get the number of columns as defined in the schema.
Schema	getProjectionSchema(String[] projcols, HashMap<Schema.ColumnSchema,HashSet<String>> keysmap) Get a projection's schema
String[]	getTypedColumns() Get the names and types of the individual columns.
static String	normalize(String value) Normalize the schema string.
static Schema	parse(String schema) Parse a schema string and create a schema object.
void	readFields(DataInput in)
String	toProjectionString() return untyped schema string for projection
String	toString() Convert the schema to a String.
void	unionSchema(Schema other) union compatible schemas.
void	write(DataOutput out)

Methods inherited from class java.lang.Object

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

Field Detail

COLUMN_DELIMITER

public static final String COLUMN_DELIMITER

See Also:

Constant Field Values

Constructor Detail

Schema

public Schema()

Constructor - schema for empty schema (zero-column) .

Schema

public Schema(boolean projection)

Constructor - schema for empty projection/schema (zero-column) .

Parameters:

projection - A projection schema or not

Schema

public Schema(String schema)
       throws ParseException

Constructor - create a schema from a string representation.

Parameters:

schema - A string representation of the schema. For this version, the schema string is simply a comma separated list of column names. Of course, comma (,) and space characters are illegal in column names. To maintain forward compatibility, please use only alpha-numeric characters in column names.

Throws:

ParseException

Schema

public Schema(String schema,
      boolean projection)
       throws ParseException

Throws:

ParseException

Schema

public Schema(Schema.ColumnSchema fs)
       throws ParseException

Throws:

ParseException

Schema

public Schema(String[] columns)
       throws ParseException

Constructor - create a schema from an array of column names.

Parameters:

columns - An array of column names. To maintain forward compatibility, please use only alpha-numeric characters in column names.

Throws:

ParseException

Method Detail

add

public void add(Schema.ColumnSchema f)
         throws ParseException

add a column

Parameters:

f - Column to be added to the schema

Throws:

ParseException

getColumn

public Schema.ColumnSchema getColumn(String name)

get a column by name

getColumns

public String[] getColumns()

Get the names of the individual columns.

Returns:

An array of the column names.

getColumn

public Schema.ColumnSchema getColumn(int index)

Get a particular column's schema

getColumnName

public String getColumnName(int index)

getTypedColumns

public String[] getTypedColumns()

Get the names and types of the individual columns.

Returns:

An array of the column names.

getColumnIndex

public int getColumnIndex(String name)

Get the index of the column for the input column name.

Parameters:

name - input column name.

Returns:

The column index if the name is valid; -1 otherwise.

getNumColumns

public int getNumColumns()

Get the number of columns as defined in the schema.

Returns:

The number of columns as defined in the schema.

parse

public static Schema parse(String schema)
                    throws ParseException

Parse a schema string and create a schema object.

Parameters:

schema - comma separated schema string.

Returns:

Schema object

Throws:

ParseException

toString

public String toString()

Convert the schema to a String.

Overrides:

toString in class Object

Returns:

the string representation of the schema.

normalize

public static String normalize(String value)

Normalize the schema string.

Parameters:

value - the input string representation of the schema.

Returns:

the normalized string representation.

compareTo

public int compareTo(Schema other)

Specified by:

compareTo in interface Comparable<Schema>

See Also:

Comparable.compareTo(Object)

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

See Also:

Object.equals(Object)

readFields

public void readFields(DataInput in)
                throws IOException

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Throws:

IOException

See Also:

Writable.readFields(DataInput)

write

public void write(DataOutput out)
           throws IOException

Specified by:

write in interface org.apache.hadoop.io.Writable

Throws:

IOException

See Also:

Writable.write(DataOutput)

getProjectionSchema

public Schema getProjectionSchema(String[] projcols,
                         HashMap<Schema.ColumnSchema,HashSet<String>> keysmap)
                           throws ParseException

Get a projection's schema

Throws:

ParseException

getColumnSchema

public Schema.ColumnSchema getColumnSchema(String name)
                                    throws ParseException

Get a column's schema

Parameters:

name - column name

Returns:

Column schema for the named column

Throws:

ParseException

getColumnSchemaOnParsedName

public Schema.ColumnSchema getColumnSchemaOnParsedName(Schema.ParsedName pn)
                                                throws ParseException

Get a subcolumn's schema and move the name just parsed into the next subtype

Parameters:

pn - The name of subcolumn to be parsed. On return it contains the subcolumn at the next level after parsing

Returns:

the discovered Column Schema for the subcolumn

Throws:

ParseException

getColumnSchema

public Schema.ColumnSchema getColumnSchema(Schema.ParsedName pn)
                                    throws ParseException

find the most fitting subcolumn containing the name: the parsed name is set after the field name plus any possible separator of '.' or '#'. This is used to help discover the most fitting column schema in multiple CG schemas. For instance, if pn contains a name of r.r1.f11 and current schema has r.r1:record(f11:int, f12), it will return f11's column schema, and pn is set at "f12".

Parameters:

pn - The name of subcolumn to be parsed. On return it contains the subcolumn at the next level after parsing

Returns:

the discovered Column Schema for the subcolumn

Throws:

ParseException

unionSchema

public void unionSchema(Schema other)
                 throws ParseException

union compatible schemas. Exception will be thrown if a name appears in multiple schemas but the types are different.

Throws:

ParseException

toProjectionString

public String toProjectionString()

return untyped schema string for projection