TableSnapshotScanner (Apache HBase 1.4.11 API)

java.lang.Object
- org.apache.hadoop.hbase.client.AbstractClientScanner
- - org.apache.hadoop.hbase.client.TableSnapshotScanner

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<Result>, ResultScanner
```
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class TableSnapshotScanner
extends AbstractClientScanner
```
A Scanner which performs a scan over snapshot files. Using this class requires copying the snapshot to a temporary empty directory, which will copy the snapshot reference files into that directory. Actual data files are not copied.
This also allows one to run the scan from an online or offline hbase cluster. The snapshot files can be exported by using the ExportSnapshot tool, to a pure-hdfs cluster, and this scanner can be used to run the scan directly over the snapshot files. The snapshot should not be deleted while there are open scanners reading from snapshot files.
An internal RegionScanner is used to execute the Scan obtained from the user for each region in the snapshot.
HBase owns all the data and snapshot files on the filesystem. Only the HBase user can read from snapshot files and data files. HBase also enforces security because all the requests are handled by the server layer, and the user cannot read from the data files directly. To read from snapshot files directly from the file system, the user who is running the MR job must have sufficient permissions to access snapshot and reference files. This means that to run mapreduce over snapshot files, the job has to be run as the HBase user or the user must have group or other priviledges in the filesystem (See HBASE-8369). Note that, given other users access to read from snapshot/data files will completely circumvent the access control enforced by HBase.

See Also:
TableSnapshotInputFormat

Field Summary
- Fields inherited from class org.apache.hadoop.hbase.client.AbstractClientScanner
  scanMetrics

Constructor Summary

Constructors
Constructor and Description
`TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.Path rootDir, org.apache.hadoop.fs.Path restoreDir, String snapshotName, Scan scan)` Creates a TableSnapshotScanner.
`TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.Path restoreDir, String snapshotName, Scan scan)` Creates a TableSnapshotScanner.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`close()` Closes the scanner and releases any resources it has allocated
`Result`	`next()` Grab the next row's worth of values.
`boolean`	`renewLease()` Allow the client to renew the scanner's lease on the server.

Methods inherited from class org.apache.hadoop.hbase.client.AbstractClientScanner
getScanMetrics, initScanMetrics, iterator, next

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - TableSnapshotScanner
```
public TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf,
                    org.apache.hadoop.fs.Path restoreDir,
                    String snapshotName,
                    Scan scan)
                     throws IOException
```
    Creates a TableSnapshotScanner.
    
    Parameters:
    conf - the configuration
    restoreDir - a temporary directory to copy the snapshot files into. Current user should have write permissions to this directory, and this should not be a subdirectory of rootdir. The scanner deletes the contents of the directory once the scanner is closed.
    snapshotName - the name of the snapshot to read from
    scan - a Scan representing scan parameters
    
    Throws:
    
    IOException - in case of error
  - TableSnapshotScanner
```
public TableSnapshotScanner(org.apache.hadoop.conf.Configuration conf,
                    org.apache.hadoop.fs.Path rootDir,
                    org.apache.hadoop.fs.Path restoreDir,
                    String snapshotName,
                    Scan scan)
                     throws IOException
```
    Creates a TableSnapshotScanner.
    
    Parameters:
    conf - the configuration
    rootDir - root directory for HBase.
    restoreDir - a temporary directory to copy the snapshot files into. Current user should have write permissions to this directory, and this should not be a subdirectory of rootdir. The scanner deletes the contents of the directory once the scanner is closed.
    snapshotName - the name of the snapshot to read from
    scan - a Scan representing scan parameters
    
    Throws:
    
    IOException - in case of error
- Method Detail
  - next
```
public Result next()
            throws IOException
```
    Description copied from interface: ResultScanner
    
    Grab the next row's worth of values. The scanner will return a Result.
    
    Returns:
    Result object if there is another row, null if the scanner is exhausted.
    
    Throws:
    
    IOException - e
  - close
```
public void close()
```
    Description copied from interface: ResultScanner
    
    Closes the scanner and releases any resources it has allocated
  - renewLease
```
public boolean renewLease()
```
    Description copied from interface: ResultScanner
    
    Allow the client to renew the scanner's lease on the server.
    
    Returns:
    true if the lease was successfully renewed, false otherwise.

Class TableSnapshotScanner

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Constructor Detail

TableSnapshotScanner

TableSnapshotScanner

Method Detail

next

close

renewLease