org.apache.pig.piggybank.storage
Class IndexedStorage

java.lang.Object
  org.apache.pig.LoadFunc
      org.apache.pig.FileInputLoadFunc
          org.apache.pig.builtin.PigStorage
              org.apache.pig.piggybank.storage.IndexedStorage

All Implemented Interfaces:

IndexableLoadFunc, LoadMetadata, LoadPushDown, OrderedLoadFunc, OverwritableStoreFunc, StoreFuncInterface, StoreMetadata

public class IndexedStorage
extends PigStorage
implements IndexableLoadFunc

IndexedStorage is a form of PigStorage that supports a per record seek. IndexedStorage creates a separate (hidden) index file for every data file that is written. The format of the index file is:

 | Header     |
 | Index Body |
 | Footer     |
 

The Header contains the list of record indices (field numbers) that represent index keys. The Index Body contains a Tuple for each record in the data. The fields of the Tuple are:

• The index key(s) Tuple
• The number of records that share this index key.
• Offset into the data file to read the first matching record.

The Footer contains sequentially:

• The smallest key(s) Tuple in the index.
• The largest key(s) Tuple in the index.
• The offset in bytes to the start of the footer

IndexStorage implements IndexableLoadFunc and can be used as the 'right table' in a PIG 'merge' or 'merge-sparse' join. IndexStorage does not require the data to be globally partitioned & sorted by index keys. Each partition (separate index) must be locally sorted. Also note IndexStorage is a loader to demonstrate "merge-sparse" join.

Nested Class Summary

static class	IndexedStorage.IndexedStorageInputFormat Internal InputFormat class
static class	IndexedStorage.IndexedStorageOutputFormat Internal OutputFormat class
static class	IndexedStorage.IndexManager IndexManager manages the index file (both writing and reading) It keeps track of the last index read during reading.

Nested classes/interfaces inherited from interface org.apache.pig.LoadPushDown

LoadPushDown.OperatorSet, LoadPushDown.RequiredField, LoadPushDown.RequiredFieldList, LoadPushDown.RequiredFieldResponse

Field Summary

protected int	currentReaderIndexStart Index into the the list of readers to the current reader.
protected byte	fieldDelimiter Delimiter to use between fields
protected int[]	offsetsToIndexKeys Offsets to index keys in tuple
protected Comparator<IndexedStorage.IndexedStorageInputFormat.IndexedStorageRecordReader>	readerComparator Comparator used to compare key tuples.
protected IndexedStorage.IndexedStorageInputFormat.IndexedStorageRecordReader[]	readers List of record readers.

Fields inherited from class org.apache.pig.builtin.PigStorage

caster, in, mLog, mRequiredColumns, schema, signature, writer

Constructor Summary

IndexedStorage(String delimiter, String offsetsToIndexKeys)
Constructs a Pig Storer that uses specified regex as a field delimiter.

Method Summary

void	close() A method called by the Pig runtime to give an opportunity for implementations to perform cleanup actions like closing the underlying input stream.
org.apache.hadoop.mapreduce.InputFormat	getInputFormat() This will be called during planning on the front end.
Tuple	getNext() Retrieves the next tuple to be processed.
org.apache.hadoop.mapreduce.OutputFormat	getOutputFormat() Return the OutputFormat associated with StoreFuncInterface.
void	initialize(org.apache.hadoop.conf.Configuration conf) IndexableLoadFunc interface implementation
void	seekNear(Tuple keys) This method is called by the Pig runtime to indicate to the LoadFunc to position its underlying input stream near the keys supplied as the argument.

Methods inherited from class org.apache.pig.builtin.PigStorage

checkSchema, cleanupOnFailure, cleanupOnSuccess, cleanupOutput, equals, equals, getFeatures, getPartitionKeys, getSchema, getStatistics, hashCode, prepareToRead, prepareToWrite, pushProjection, putNext, readField, relToAbsPathForStoreLocation, setLocation, setPartitionFilter, setStoreFuncUDFContextSignature, setStoreLocation, setUDFContextSignature, shouldOverwrite, storeSchema, storeStatistics

Methods inherited from class org.apache.pig.FileInputLoadFunc

getSplitComparable

Methods inherited from class org.apache.pig.LoadFunc

getAbsolutePath, getLoadCaster, getPathStrings, join, relativeToAbsolutePath, warn

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

readers

protected IndexedStorage.IndexedStorageInputFormat.IndexedStorageRecordReader[] readers

List of record readers.

currentReaderIndexStart

protected int currentReaderIndexStart

Index into the the list of readers to the current reader. Readers before this index have been fully scanned for keys.

fieldDelimiter

protected byte fieldDelimiter

Delimiter to use between fields

offsetsToIndexKeys

protected final int[] offsetsToIndexKeys

Offsets to index keys in tuple

readerComparator

protected Comparator<IndexedStorage.IndexedStorageInputFormat.IndexedStorageRecordReader> readerComparator

Comparator used to compare key tuples.

Constructor Detail

IndexedStorage

public IndexedStorage(String delimiter,
                      String offsetsToIndexKeys)

Constructs a Pig Storer that uses specified regex as a field delimiter.

Parameters:

delimiter - - field delimiter to use

offsetsToIndexKeys - - list of offset into Tuple for index keys (comma separated)

Method Detail

getOutputFormat

public org.apache.hadoop.mapreduce.OutputFormat getOutputFormat()

Description copied from interface: StoreFuncInterface

Return the OutputFormat associated with StoreFuncInterface. This will be called on the front end during planning and on the backend during execution.

Specified by:

getOutputFormat in interface StoreFuncInterface

Overrides:

getOutputFormat in class PigStorage

Returns:

the OutputFormat associated with StoreFuncInterface

getInputFormat

public org.apache.hadoop.mapreduce.InputFormat getInputFormat()

Description copied from class: LoadFunc

This will be called during planning on the front end. This is the instance of InputFormat (rather than the class name) because the load function may need to instantiate the InputFormat in order to control how it is constructed.

Overrides:

getInputFormat in class PigStorage

Returns:

the InputFormat associated with this loader.

getNext

public Tuple getNext()
              throws IOException

Description copied from class: LoadFunc

Retrieves the next tuple to be processed. Implementations should NOT reuse tuple objects (or inner member objects) they return across calls and should return a different tuple object in each call.

Overrides:

getNext in class PigStorage

Returns:

the next tuple to be processed or null if there are no more tuples to be processed.

Throws:

IOException - if there is an exception while retrieving the next tuple

initialize

public void initialize(org.apache.hadoop.conf.Configuration conf)
                throws IOException

IndexableLoadFunc interface implementation

Specified by:

initialize in interface IndexableLoadFunc

Parameters:

conf - The job configuration object

Throws:

IOException

seekNear

public void seekNear(Tuple keys)
              throws IOException

Description copied from interface: IndexableLoadFunc

This method is called by the Pig runtime to indicate to the LoadFunc to position its underlying input stream near the keys supplied as the argument. Specifically: 1) if the keys are present in the input stream, the loadfunc implementation should position its read position to a record where the key(s) is/are the biggest key(s) less than the key(s) supplied in the argument OR to the record with the first occurrence of the keys(s) supplied. 2) if the key(s) are absent in the input stream, the implementation should position its read position to a record where the key(s) is/are the biggest key(s) less than the key(s) supplied OR to the first record where the key(s) is/are the smallest key(s) greater than the keys(s) supplied. The description above holds for descending order data in a similar manner with "biggest" and "less than" replaced with "smallest" and "greater than" and vice versa.

Specified by:

seekNear in interface IndexableLoadFunc

Parameters:

keys - Tuple with join keys (which are a prefix of the sort keys of the input data). For example if the data is sorted on columns in position 2,4,5 any of the following Tuples are valid as an argument value: (fieldAt(2)) (fieldAt(2), fieldAt(4)) (fieldAt(2), fieldAt(4), fieldAt(5)) The following are some invalid cases: (fieldAt(4)) (fieldAt(2), fieldAt(5)) (fieldAt(4), fieldAt(5))

Throws:

IOException - When the loadFunc is unable to position to the required point in its input stream

close

public void close()
           throws IOException

Description copied from interface: IndexableLoadFunc

A method called by the Pig runtime to give an opportunity for implementations to perform cleanup actions like closing the underlying input stream. This is necessary since while performing a join the Pig run time may determine than no further join is possible with remaining records and may indicate to the IndexableLoader to cleanup by calling this method.

Specified by:

close in interface IndexableLoadFunc

Throws:

IOException - if the loadfunc is unable to perform its close actions.