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

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

static String

COLUMN_DELIMITER

Constructor Summary

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

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