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
public class Get
extends Query
implements 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

colFamTimeRangeMap, consistency, filter, loadColumnFamiliesOnDemand, targetReplicaId

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

ID_ATRIBUTE

Fields inherited from interface org.apache.hadoop.hbase.client.Row

COMPARATOR

Constructor Summary

Constructors

Constructor and Description
Get(byte[] row) Create a Get operation for the specified row.
Get(byte[] row, int rowOffset, int rowLength) Create a Get operation for the specified row.
Get(ByteBuffer row) Create a Get operation for the specified row.
Get(Get get) Copy-constructor n

Method Summary

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) Compare this row to another row.
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 n
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 n
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 n
boolean	hasFamilies() Method for checking if any families have been inserted into this Get
int	hashCode()
boolean	isCheckExistenceOnly()
boolean	isClosestRowBefore() Deprecated. since 2.0.0 and will be removed in 3.0.0
int	numFamilies() Method for retrieving the number of families to get from
Get	readAllVersions() Get all available versions.
Get	readVersions(int versions) Get up to the specified number of versions of each column.
Get	setACL(Map<String,org.apache.hadoop.hbase.security.access.Permission> perms) Set the ACL for the operation.
Get	setACL(String user, org.apache.hadoop.hbase.security.access.Permission perms) Set the ACL for the operation.
Get	setAttribute(String name, byte[] value) Sets an attribute.
Get	setAuthorizations(org.apache.hadoop.hbase.security.visibility.Authorizations authorizations) Sets the authorizations to be used by this Query n
Get	setCacheBlocks(boolean cacheBlocks) Set whether blocks should be cached for this Get.
Get	setCheckExistenceOnly(boolean checkExistenceOnly)
Get	setClosestRowBefore(boolean closestRowBefore) Deprecated. since 2.0.0 and will be removed in 3.0.0
Get	setColumnFamilyTimeRange(byte[] cf, long minStamp, long maxStamp) Get versions of columns only within the specified timestamp range, [minStamp, maxStamp) on a per CF bases.
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	setLoadColumnFamiliesOnDemand(boolean value) Set the value indicating whether loading CFs on demand should be allowed (cluster default is false).
Get	setMaxResultsPerColumnFamily(int limit) Set the maximum number of values to return per row per Column Family
Get	setMaxVersions() Deprecated. It is easy to misunderstand with column family's max versions, so use readAllVersions() instead.
Get	setMaxVersions(int maxVersions) Deprecated. It is easy to misunderstand with column family's max versions, so use readVersions(int) instead.
Get	setPriority(int priority)
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.
Get	setTimeStamp(long timestamp) Deprecated. As of release 2.0.0, this will be removed in HBase 3.0.0. Use setTimestamp(long) instead
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

doLoadColumnFamiliesOnDemand, getACL, getAuthorizations, getColumnFamilyTimeRange, getConsistency, getFilter, getIsolationLevel, getLoadColumnFamiliesOnDemandValue, getReplicaId

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

getAttribute, getAttributeSize, getAttributesMap, getId, getPriority

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 n

Get

public Get(byte[] row,
           int rowOffset,
           int rowLength)

Create a Get operation for the specified row. nnn

Get

public Get(ByteBuffer row)

Create a Get operation for the specified row. n

Method Detail

isCheckExistenceOnly

public boolean isCheckExistenceOnly()

setCheckExistenceOnly

public Get setCheckExistenceOnly(boolean checkExistenceOnly)

isClosestRowBefore

@Deprecated
public boolean isClosestRowBefore()

Deprecated. since 2.0.0 and will be removed in 3.0.0

This will always return the default value which is false as client cannot set the value to this property any more.

setClosestRowBefore

@Deprecated
public Get setClosestRowBefore(boolean closestRowBefore)

Deprecated. since 2.0.0 and will be removed in 3.0.0

This is not used any more and does nothing. Use reverse scan instead.

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 n * @return this for invocation chaining

Throws:

IOException

setTimeStamp

@Deprecated
public Get setTimeStamp(long timestamp)
                             throws IOException

Deprecated. As of release 2.0.0, this will be removed in HBase 3.0.0. Use setTimestamp(long) instead

Get versions of columns with the specified timestamp.

Parameters:

timestamp - version timestamp

Returns:

this for invocation chaining

Throws:

IOException

setTimestamp

public Get setTimestamp(long timestamp)

Get versions of columns with the specified timestamp.

Parameters:

timestamp - version timestamp

Returns:

this for invocation chaining

setColumnFamilyTimeRange

public Get setColumnFamilyTimeRange(byte[] cf,
                                    long minStamp,
                                    long maxStamp)

Description copied from class: Query

Get versions of columns only within the specified timestamp range, [minStamp, maxStamp) on a per CF bases. Note, default maximum versions to return is 1. If your time range spans more than one version and you want all versions returned, up the number of versions beyond the default. Column Family time ranges take precedence over the global time range.

Overrides:

setColumnFamilyTimeRange in class Query

Parameters:

cf - the column family for which you want to restrict

minStamp - minimum timestamp value, inclusive

maxStamp - maximum timestamp value, exclusive n

setMaxVersions

@Deprecated
public Get setMaxVersions()

Deprecated. It is easy to misunderstand with column family's max versions, so use readAllVersions() instead.

Get all available versions.

Returns:

this for invocation chaining

setMaxVersions

@Deprecated
public Get setMaxVersions(int maxVersions)
                               throws IOException

Deprecated. It is easy to misunderstand with column family's max versions, so use readVersions(int) instead.

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

readAllVersions

public Get readAllVersions()

Get all available versions.

Returns:

this for invocation chaining

readVersions

public Get readVersions(int versions)
                 throws IOException

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

Parameters:

versions - specified number of versions for each column

Returns:

this for invocation chaining

Throws:

IOException - if invalid number of versions

setLoadColumnFamiliesOnDemand

public Get setLoadColumnFamiliesOnDemand(boolean value)

Description copied from class: Query

Set the value indicating whether loading CFs on demand should be allowed (cluster default is false). On-demand CF loading doesn't load column families until necessary, e.g. if you filter on one column, the other column family data will be loaded only for the rows that are included in result, not all rows like in normal case. With column-specific filters, like SingleColumnValueFilter w/filterIfMissing == true, this can deliver huge perf gains when there's a cf with lots of data; however, it can also lead to some inconsistent results, as follows: - if someone does a concurrent update to both column families in question you may get a row that never existed, e.g. for { rowKey = 5, { cat_videos => 1 }, { video => "my cat" } } someone puts rowKey 5 with { cat_videos => 0 }, { video => "my dog" }, concurrent scan filtering on "cat_videos == 1" can get { rowKey = 5, { cat_videos => 1 }, { video => "my dog" } }. - if there's a concurrent split and you have more than 2 column families, some rows may be missing some column families.

Overrides:

setLoadColumnFamiliesOnDemand in class Query

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.filterCell(org.apache.hadoop.hbase.Cell) is called AFTER all tests for ttl, column match, deletes and column family's 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 n

Specified by:

getRow in interface 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 n

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 n

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. n

Specified by:

getFingerprint in class Operation

Returns:

a map containing fingerprint information (i.e. column families)

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 n

Returns:

a map containing parameters of a query (i.e. rows, columns...)

compareTo

public int compareTo(Row other)

Description copied from interface: Row

Compare this row to another row.

Specified by:

compareTo in interface Comparable<Row>

Specified by:

compareTo in interface 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. n * id to set for the scan

Overrides:

setId in class OperationWithAttributes

setAuthorizations

public Get setAuthorizations(org.apache.hadoop.hbase.security.visibility.Authorizations authorizations)

Description copied from class: Query

Sets the authorizations to be used by this Query n

Overrides:

setAuthorizations in class Query

setACL

public Get setACL(Map<String,org.apache.hadoop.hbase.security.access.Permission> perms)

Description copied from class: Query

Set the ACL for the operation.

Overrides:

setACL in class Query

Parameters:

perms - A map of permissions for a user or users

setACL

public Get setACL(String user,
                  org.apache.hadoop.hbase.security.access.Permission perms)

Description copied from class: Query

Set the ACL for the operation.

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 n

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

setPriority

public Get setPriority(int priority)

Overrides:

setPriority in class OperationWithAttributes