org.apache.hadoop.hbase.client

Class Get

java.lang.Object

org.apache.hadoop.hbase.client.Operation

org.apache.hadoop.hbase.client.OperationWithAttributes

org.apache.hadoop.hbase.client.Query

org.apache.hadoop.hbase.client.Get

All Implemented Interfaces:

Comparable<Row>, Attributes, Row

@InterfaceAudience.Public
@InterfaceStability.Stable
public class Get
extends Query
implements Row, Comparable<Row>

Used to perform Get operations on a single row.

To get everything for a row, instantiate a Get object with the row to get. To further narrow the scope of what to Get, use the methods below.

To get all columns from specific families, execute addFamily for each family to retrieve.

To get specific columns, execute addColumn for each column to retrieve.

To only retrieve columns within a specific range of version timestamps, execute setTimeRange.

To only retrieve columns with a specific timestamp, execute setTimestamp.

To limit the number of versions of each column to be returned, execute setMaxVersions.

To add a filter, call setFilter.

Field Summary

Fields inherited from class org.apache.hadoop.hbase.client.Query

consistency, filter, targetReplicaId

Fields inherited from class org.apache.hadoop.hbase.client.OperationWithAttributes

ID_ATRIBUTE

Constructor Summary

Constructors

Constructor and Description
Get(byte[] row) Create a Get operation for the specified row.
Get(Get get) Copy-constructor

Method Summary

Methods

Modifier and Type	Method and Description
Get	addColumn(byte[] family, byte[] qualifier) Get the column from the specific family with the specified qualifier.
Get	addFamily(byte[] family) Get all columns from the specified family.
int	compareTo(Row other)
boolean	equals(Object obj)
Set<byte[]>	familySet() Method for retrieving the keys in the familyMap
boolean	getCacheBlocks() Get whether blocks should be cached for this Get.
Map<byte[],NavigableSet<byte[]>>	getFamilyMap() Method for retrieving the get's familyMap
Map<String,Object>	getFingerprint() Compile the table and column family (i.e.
int	getMaxResultsPerColumnFamily() Method for retrieving the get's maximum number of values to return per Column Family
int	getMaxVersions() Method for retrieving the get's maximum number of version
byte[]	getRow() Method for retrieving the get's row
int	getRowOffsetPerColumnFamily() Method for retrieving the get's offset per row per column family (#kvs to be skipped)
TimeRange	getTimeRange() Method for retrieving the get's TimeRange
boolean	hasFamilies() Method for checking if any families have been inserted into this Get
int	hashCode()
boolean	isCheckExistenceOnly()
boolean	isClosestRowBefore()
int	numFamilies() Method for retrieving the number of families to get from
Get	setACL(Map<String,Permission> perms)
Get	setACL(String user, Permission perms)
Get	setAttribute(String name, byte[] value) Sets an attribute.
Get	setAuthorizations(Authorizations authorizations) Sets the authorizations to be used by this Query
Get	setCacheBlocks(boolean cacheBlocks) Set whether blocks should be cached for this Get.
Get	setCheckExistenceOnly(boolean checkExistenceOnly)
Get	setClosestRowBefore(boolean closestRowBefore)
Get	setConsistency(Consistency consistency) Sets the consistency level for this operation
Get	setFilter(Filter filter) Apply the specified server-side filter when performing the Query.
Get	setId(String id) This method allows you to set an identifier on an operation.
Get	setIsolationLevel(IsolationLevel level) Set the isolation level for this query.
Get	setMaxResultsPerColumnFamily(int limit) Set the maximum number of values to return per row per Column Family
Get	setMaxVersions() Get all available versions.
Get	setMaxVersions(int maxVersions) Get up to the specified number of versions of each column.
Get	setReplicaId(int Id) Specify region replica id where Query will fetch data from.
Get	setRowOffsetPerColumnFamily(int offset) Set offset for the row per Column Family.
Get	setTimeRange(long minStamp, long maxStamp) Get versions of columns only within the specified timestamp range, [minStamp, maxStamp).
Get	setTimeStamp(long timestamp) Get versions of columns with the specified timestamp.
Map<String,Object>	toMap(int maxCols) Compile the details beyond the scope of getFingerprint (row, columns, timestamps, etc.) into a Map along with the fingerprinted information.

Methods inherited from class org.apache.hadoop.hbase.client.Query

getACL, getAuthorizations, getConsistency, getFilter, getIsolationLevel, getReplicaId

Methods inherited from class org.apache.hadoop.hbase.client.OperationWithAttributes

getAttribute, getAttributeSize, getAttributesMap, getId

Methods inherited from class org.apache.hadoop.hbase.client.Operation

toJSON, toJSON, toMap, toString, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

Get

public Get(byte[] row)

Create a Get operation for the specified row.

If no further operations are done, this will get the latest version of all columns in all families of the specified row.

Parameters:

row - row key

Get

public Get(Get get)

Copy-constructor

Parameters:

get -

Method Detail

isCheckExistenceOnly

public boolean isCheckExistenceOnly()

setCheckExistenceOnly

public Get setCheckExistenceOnly(boolean checkExistenceOnly)

isClosestRowBefore

public boolean isClosestRowBefore()

setClosestRowBefore

public Get setClosestRowBefore(boolean closestRowBefore)

addFamily

public Get addFamily(byte[] family)

Get all columns from the specified family.

Overrides previous calls to addColumn for this family.

Parameters:

family - family name

Returns:

the Get object

addColumn

public Get addColumn(byte[] family,
            byte[] qualifier)

Get the column from the specific family with the specified qualifier.

Overrides previous calls to addFamily for this family.

Parameters:

family - family name

qualifier - column qualifier

Returns:

the Get objec

setTimeRange

public Get setTimeRange(long minStamp,
               long maxStamp)
                 throws IOException

Get versions of columns only within the specified timestamp range, [minStamp, maxStamp).

Parameters:

minStamp - minimum timestamp value, inclusive

maxStamp - maximum timestamp value, exclusive

Returns:

this for invocation chaining

Throws:

IOException - if invalid time range

setTimeStamp

public Get setTimeStamp(long timestamp)
                 throws IOException

Get versions of columns with the specified timestamp.

Parameters:

timestamp - version timestamp

Returns:

this for invocation chaining

Throws:

IOException

setMaxVersions

public Get setMaxVersions()

Get all available versions.

Returns:

this for invocation chaining

setMaxVersions

public Get setMaxVersions(int maxVersions)
                   throws IOException

Get up to the specified number of versions of each column.

Parameters:

maxVersions - maximum versions for each column

Returns:

this for invocation chaining

Throws:

IOException - if invalid number of versions

setMaxResultsPerColumnFamily

public Get setMaxResultsPerColumnFamily(int limit)

Set the maximum number of values to return per row per Column Family

Parameters:

limit - the maximum number of values returned / row / CF

Returns:

this for invocation chaining

setRowOffsetPerColumnFamily

public Get setRowOffsetPerColumnFamily(int offset)

Set offset for the row per Column Family. This offset is only within a particular row/CF combination. It gets reset back to zero when we move to the next row or CF.

Parameters:

offset - is the number of kvs that will be skipped.

Returns:

this for invocation chaining

setFilter

public Get setFilter(Filter filter)

Description copied from class: Query

Apply the specified server-side filter when performing the Query. Only Filter.filterKeyValue(Cell) is called AFTER all tests for ttl, column match, deletes and max versions have been run.

Overrides:

setFilter in class Query

Parameters:

filter - filter to run on the server

Returns:

this for invocation chaining

setCacheBlocks

public Get setCacheBlocks(boolean cacheBlocks)

Set whether blocks should be cached for this Get.

This is true by default. When true, default settings of the table and family are used (this will never override caching blocks if the block cache is disabled for that family or entirely).

Parameters:

cacheBlocks - if false, default settings are overridden and blocks will not be cached

getCacheBlocks

public boolean getCacheBlocks()

Get whether blocks should be cached for this Get.

Returns:

true if default caching should be used, false if blocks should not be cached

getRow

public byte[] getRow()

Method for retrieving the get's row

Specified by:

getRow in interface Row

Returns:

row

getMaxVersions

public int getMaxVersions()

Method for retrieving the get's maximum number of version

Returns:

the maximum number of version to fetch for this get

getMaxResultsPerColumnFamily

public int getMaxResultsPerColumnFamily()

Method for retrieving the get's maximum number of values to return per Column Family

Returns:

the maximum number of values to fetch per CF

getRowOffsetPerColumnFamily

public int getRowOffsetPerColumnFamily()

Method for retrieving the get's offset per row per column family (#kvs to be skipped)

Returns:

the row offset

getTimeRange

public TimeRange getTimeRange()

Method for retrieving the get's TimeRange

Returns:

timeRange

familySet

public Set<byte[]> familySet()

Method for retrieving the keys in the familyMap

Returns:

keys in the current familyMap

numFamilies

public int numFamilies()

Method for retrieving the number of families to get from

Returns:

number of families

hasFamilies

public boolean hasFamilies()

Method for checking if any families have been inserted into this Get

Returns:

true if familyMap is non empty false otherwise

getFamilyMap

public Map<byte[],NavigableSet<byte[]>> getFamilyMap()

Method for retrieving the get's familyMap

Returns:

familyMap

getFingerprint

public Map<String,Object> getFingerprint()

Compile the table and column family (i.e. schema) information into a String. Useful for parsing and aggregation by debugging, logging, and administration tools.

Specified by:

getFingerprint in class Operation

Returns:

Map

toMap

public Map<String,Object> toMap(int maxCols)

Compile the details beyond the scope of getFingerprint (row, columns, timestamps, etc.) into a Map along with the fingerprinted information. Useful for debugging, logging, and administration tools.

Specified by:

toMap in class Operation

Parameters:

maxCols - a limit on the number of columns output prior to truncation

Returns:

Map

compareTo

public int compareTo(Row other)

Specified by:

compareTo in interface Comparable<Row>

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

setAttribute

public Get setAttribute(String name,
               byte[] value)

Description copied from interface: Attributes

Sets an attribute. In case value = null attribute is removed from the attributes map. Attribute names starting with _ indicate system attributes.

Specified by:

setAttribute in interface Attributes

Overrides:

setAttribute in class OperationWithAttributes

Parameters:

name - attribute name

value - attribute value

setId

public Get setId(String id)

Description copied from class: OperationWithAttributes

This method allows you to set an identifier on an operation. The original motivation for this was to allow the identifier to be used in slow query logging, but this could obviously be useful in other places. One use of this could be to put a class.method identifier in here to see where the slow query is coming from.

Overrides:

setId in class OperationWithAttributes

Parameters:

id - id to set for the scan

setAuthorizations

public Get setAuthorizations(Authorizations authorizations)

Description copied from class: Query

Sets the authorizations to be used by this Query

Overrides:

setAuthorizations in class Query

setACL

public Get setACL(Map<String,Permission> perms)

Overrides:

setACL in class Query

Parameters:

perms - A map of permissions for a user or users

setACL

public Get setACL(String user,
         Permission perms)

Overrides:

setACL in class Query

Parameters:

user - User short name

perms - Permissions for the user

setConsistency

public Get setConsistency(Consistency consistency)

Description copied from class: Query

Sets the consistency level for this operation

Overrides:

setConsistency in class Query

Parameters:

consistency - the consistency level

setReplicaId

public Get setReplicaId(int Id)

Description copied from class: Query

Specify region replica id where Query will fetch data from. Use this together with Query.setConsistency(Consistency) passing Consistency.TIMELINE to read data from a specific replicaId.
Expert: This is an advanced API exposed. Only use it if you know what you are doing

Overrides:

setReplicaId in class Query

setIsolationLevel

public Get setIsolationLevel(IsolationLevel level)

Description copied from class: Query

Set the isolation level for this query. If the isolation level is set to READ_UNCOMMITTED, then this query will return data from committed and uncommitted transactions. If the isolation level is set to READ_COMMITTED, then this query will return data from committed transactions only. If a isolation level is not explicitly set on a Query, then it is assumed to be READ_COMMITTED.

Overrides:

setIsolationLevel in class Query

Parameters:

level - IsolationLevel for this query