ClientScanner (Apache HBase 1.2.12 API)

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

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<Result>, ResultScanner

Direct Known Subclasses:

ClientSmallScanner, ReversedClientScanner
```
@InterfaceAudience.Private
public class ClientScanner
extends AbstractClientScanner
```
Implements the scanner interface for the HBase client. If there are multiple regions in a table, this scanner will iterate through them all.

Field Summary

Fields
Modifier and Type	Field and Description
`protected LinkedList<Result>`	`cache`
`protected int`	`caching`
`protected ScannerCallableWithReplicas`	`callable`
`protected RpcRetryingCaller<Result[]>`	`caller`
`protected boolean`	`closed`
`protected org.apache.hadoop.conf.Configuration`	`conf`
`private ClusterConnection`	`connection`
`protected HRegionInfo`	`currentRegion`
`protected Cell`	`lastCellLoadedToCache` The last cell from a not full Row which is added to cache
`protected long`	`lastNext`
`protected Result`	`lastResult`
`private static org.apache.commons.logging.Log`	`LOG`
`(package private) static byte[]`	`MAX_BYTE_ARRAY`
`protected long`	`maxScannerResultSize`
`private static KeyValue.MetaComparator`	`metaComparator`
`protected LinkedList<Result>`	`partialResults` A list of partial results that have been returned from the server.
`protected byte[]`	`partialResultsRow` The row for which we are accumulating partial Results (i.e.
`protected ExecutorService`	`pool`
`protected int`	`primaryOperationTimeout`
`private int`	`retries`
`protected RpcControllerFactory`	`rpcControllerFactory`
`protected Scan`	`scan`
`protected boolean`	`scanMetricsPublished`
`protected int`	`scannerTimeout`
`private TableName`	`tableName`

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

Constructor Summary

Constructors
Constructor and Description
`ClientScanner(org.apache.hadoop.conf.Configuration conf, Scan scan, TableName tableName, ClusterConnection connection, RpcRetryingCallerFactory rpcFactory, RpcControllerFactory controllerFactory, ExecutorService pool, int primaryOperationTimeout)` Create a new ClientScanner for the specified table Note that the passed `Scan`'s start row maybe changed changed.

Method Summary

Methods
Modifier and Type	Method and Description
`private void`	`addResultsToList(List<Result> outputList, Result[] inputArray, int start, int end)` Helper method for adding results between the indices [start, end) to the outputList
`private void`	`addToPartialResults(Result result)` A convenience method for adding a Result to our list of partials.
`(package private) Result[]`	`call(ScannerCallableWithReplicas callable, RpcRetryingCaller<Result[]> caller, int scannerTimeout)`
`protected boolean`	`checkScanStopRow(byte[] endKey)`
`private void`	`clearPartialResults()` Convenience method for clearing the list of partials and resetting the partialResultsRow.
`void`	`close()` Closes the scanner and releases any resources it has allocated
`private int`	`compare(Cell a, Cell b)` Compare two Cells considering reversed scanner.
`protected static byte[]`	`createClosestRowBefore(byte[] row)` Create the closest row before the specified row
`private boolean`	`doneWithRegion(long remainingResultSize, int remainingRows, boolean regionHasMoreResults)`
`private Result`	`filterLoadedCell(Result result)`
`int`	`getCacheSize()`
`protected int`	`getCaching()`
`protected org.apache.hadoop.conf.Configuration`	`getConf()`
`protected ClusterConnection`	`getConnection()`
`protected long`	`getMaxResultSize()`
`protected ExecutorService`	`getPool()`
`protected int`	`getPrimaryOperationTimeout()`
`protected List<Result>`	`getResultsToAddToCache(Result[] resultsFromServer, boolean heartbeatMessage)` This method ensures all of our book keeping regarding partial results is kept up to date.
`protected int`	`getRetries()`
`protected Scan`	`getScan()`
`protected ScannerCallableWithReplicas`	`getScannerCallable(byte[] localStartKey, int nbRows)`
`protected int`	`getScannerTimeout()`
`protected TableName`	`getTable()`
`protected byte[]`	`getTableName()` Deprecated. As of release 0.96 (HBASE-9508). This will be removed in HBase 2.0.0. Use `getTable()`.
`protected long`	`getTimestamp()`
`protected void`	`initializeScannerInConstruction()`
`(package private) boolean`	`isAnyRPCcancelled()`
`protected void`	`loadCache()` Contact the servers to load more `Result`s in the cache.
`Result`	`next()` Grab the next row's worth of values.
`protected boolean`	`nextScanner(int nbRows, boolean done)`
`private boolean`	`possiblyNextScanner(int nbRows, boolean done)`
`boolean`	`renewLease()` Allow the client to renew the scanner's lease on the server.
`protected void`	`updateLastCellLoadedToCache(Result result)`
`protected void`	`writeScanMetrics()` Publish the scan metrics.

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

- Field Detail
  - LOG
```
private static final org.apache.commons.logging.Log LOG
```
  - MAX_BYTE_ARRAY
```
static byte[] MAX_BYTE_ARRAY
```
  - scan
```
protected Scan scan
```
  - closed
```
protected boolean closed
```
  - currentRegion
```
protected HRegionInfo currentRegion
```
  - callable
```
protected ScannerCallableWithReplicas callable
```
  - cache
```
protected final LinkedList<Result> cache
```
  - partialResults
```
protected final LinkedList<Result> partialResults
```
    A list of partial results that have been returned from the server. This list should only contain results if this scanner does not have enough partial results to form the complete result.
  - partialResultsRow
```
protected byte[] partialResultsRow
```
    The row for which we are accumulating partial Results (i.e. the row of the Results stored inside partialResults). Changes to partialResultsRow and partialResults are kept in sync via the methods addToPartialResults(Result) and clearPartialResults()
  - lastCellLoadedToCache
```
protected Cell lastCellLoadedToCache
```
    The last cell from a not full Row which is added to cache
  - caching
```
protected final int caching
```
  - lastNext
```
protected long lastNext
```
  - lastResult
```
protected Result lastResult
```
  - maxScannerResultSize
```
protected final long maxScannerResultSize
```
  - connection
```
private final ClusterConnection connection
```
  - tableName
```
private final TableName tableName
```
  - scannerTimeout
```
protected final int scannerTimeout
```
  - scanMetricsPublished
```
protected boolean scanMetricsPublished
```
  - caller
```
protected RpcRetryingCaller<Result[]> caller
```
  - rpcControllerFactory
```
protected RpcControllerFactory rpcControllerFactory
```
  - conf
```
protected org.apache.hadoop.conf.Configuration conf
```
  - primaryOperationTimeout
```
protected final int primaryOperationTimeout
```
  - retries
```
private int retries
```
  - pool
```
protected final ExecutorService pool
```
  - metaComparator
```
private static KeyValue.MetaComparator metaComparator
```
- Constructor Detail
  - ClientScanner
```
public ClientScanner(org.apache.hadoop.conf.Configuration conf,
             Scan scan,
             TableName tableName,
             ClusterConnection connection,
             RpcRetryingCallerFactory rpcFactory,
             RpcControllerFactory controllerFactory,
             ExecutorService pool,
             int primaryOperationTimeout)
              throws IOException
```
    Create a new ClientScanner for the specified table Note that the passed Scan's start row maybe changed changed.
    
    Parameters:
    conf - The Configuration to use.
    scan - Scan to use in this scanner
    tableName - The table that we wish to scan
    connection - Connection identifying the cluster
    
    Throws:
    
    IOException
- Method Detail
  - initializeScannerInConstruction
```
protected void initializeScannerInConstruction()
                                        throws IOException
```
    Throws:
    
    IOException
  - getConnection
```
protected ClusterConnection getConnection()
```
  - getTableName
```
@Deprecated
protected byte[] getTableName()
```
    Deprecated. As of release 0.96 (HBASE-9508). This will be removed in HBase 2.0.0. Use getTable().
    
    Returns:
    Table name
  - getTable
```
protected TableName getTable()
```
  - getRetries
```
protected int getRetries()
```
  - getScannerTimeout
```
protected int getScannerTimeout()
```
  - getConf
```
protected org.apache.hadoop.conf.Configuration getConf()
```
  - getScan
```
protected Scan getScan()
```
  - getPool
```
protected ExecutorService getPool()
```
  - getPrimaryOperationTimeout
```
protected int getPrimaryOperationTimeout()
```
  - getCaching
```
protected int getCaching()
```
  - getTimestamp
```
protected long getTimestamp()
```
  - getMaxResultSize
```
protected long getMaxResultSize()
```
  - checkScanStopRow
```
protected boolean checkScanStopRow(byte[] endKey)
```
  - possiblyNextScanner
```
private boolean possiblyNextScanner(int nbRows,
                          boolean done)
                             throws IOException
```
    Throws:
    
    IOException
  - nextScanner
```
protected boolean nextScanner(int nbRows,
                  boolean done)
                       throws IOException
```
    Throws:
    
    IOException
  - isAnyRPCcancelled
```
boolean isAnyRPCcancelled()
```
  - call
```
Result[] call(ScannerCallableWithReplicas callable,
            RpcRetryingCaller<Result[]> caller,
            int scannerTimeout)
        throws IOException,
               RuntimeException
```
    Throws:
    
    IOException
    
    RuntimeException
  - getScannerCallable
```
@InterfaceAudience.Private
protected ScannerCallableWithReplicas getScannerCallable(byte[] localStartKey,
                                                                       int nbRows)
```
  - writeScanMetrics
```
protected void writeScanMetrics()
```
    Publish the scan metrics. For now, we use scan.setAttribute to pass the metrics back to the application or TableInputFormat.Later, we could push it to other systems. We don't use metrics framework because it doesn't support multi-instances of the same metrics on the same machine; for scan/map reduce scenarios, we will have multiple scans running at the same time. By default, scan metrics are disabled; if the application wants to collect them, this behavior can be turned on by calling calling Scan.setScanMetricsEnabled(boolean)
    This invocation clears the scan metrics. Metrics are aggregated in the Scan instance.
  - 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
  - getCacheSize
```
public int getCacheSize()
```
  - loadCache
```
protected void loadCache()
                  throws IOException
```
    Contact the servers to load more Results in the cache.
    
    Throws:
    
    IOException
  - doneWithRegion
```
private boolean doneWithRegion(long remainingResultSize,
                     int remainingRows,
                     boolean regionHasMoreResults)
```
    Parameters:
    remainingResultSize -
    remainingRows -
    regionHasMoreResults -
    
    Returns:
    true when the current region has been exhausted. When the current region has been exhausted, the region must be changed before scanning can continue
  - getResultsToAddToCache
```
protected List<Result> getResultsToAddToCache(Result[] resultsFromServer,
                                  boolean heartbeatMessage)
                                       throws IOException
```
    This method ensures all of our book keeping regarding partial results is kept up to date. This method should be called once we know that the results we received back from the RPC request do not contain errors. We return a list of results that should be added to the cache. In general, this list will contain all NON-partial results from the input array (unless the client has specified that they are okay with receiving partial results)
    
    Parameters:
    resultsFromServer - The array of Results returned from the server
    heartbeatMessage - Flag indicating whether or not the response received from the server represented a complete response, or a heartbeat message that was sent to keep the client-server connection alive
    
    Returns:
    the list of results that should be added to the cache.
    
    Throws:
    
    IOException
  - addToPartialResults
```
private void addToPartialResults(Result result)
                          throws IOException
```
    A convenience method for adding a Result to our list of partials. This method ensure that only Results that belong to the same row as the other partials can be added to the list.
    
    Parameters:
    result - The result that we want to add to our list of partial Results
    
    Throws:
    
    IOException
  - clearPartialResults
```
private void clearPartialResults()
```
    Convenience method for clearing the list of partials and resetting the partialResultsRow.
  - addResultsToList
```
private void addResultsToList(List<Result> outputList,
                    Result[] inputArray,
                    int start,
                    int end)
```
    Helper method for adding results between the indices [start, end) to the outputList
    
    Parameters:
    outputList - the list that results will be added to
    inputArray - the array that results are taken from
    start - beginning index (inclusive)
    end - ending index (exclusive)
  - close
```
public void close()
```
    Description copied from interface: ResultScanner
    
    Closes the scanner and releases any resources it has allocated
  - createClosestRowBefore
```
protected static byte[] createClosestRowBefore(byte[] row)
```
    Create the closest row before the specified row
    
    Parameters:
    row -
    
    Returns:
    a new byte array which is the closest front row of the specified one
  - renewLease
```
public boolean renewLease()
```
    Description copied from class: AbstractClientScanner
    
    Allow the client to renew the scanner's lease on the server.
    
    Specified by:
    
    renewLease in class AbstractClientScanner
    
    Returns:
    true if the lease was successfully renewed, false otherwise.
  - updateLastCellLoadedToCache
```
protected void updateLastCellLoadedToCache(Result result)
```
  - compare
```
private int compare(Cell a,
          Cell b)
```
    Compare two Cells considering reversed scanner. ReversedScanner only reverses rows, not columns.
  - filterLoadedCell
```
private Result filterLoadedCell(Result result)
```

Class ClientScanner

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

Field Detail

LOG

MAX_BYTE_ARRAY

scan

closed

currentRegion

callable

cache

partialResults

partialResultsRow

lastCellLoadedToCache

caching

lastNext

lastResult

maxScannerResultSize

connection

tableName

scannerTimeout

scanMetricsPublished

caller

rpcControllerFactory

conf

primaryOperationTimeout

retries

pool

metaComparator

Constructor Detail

ClientScanner

Method Detail

initializeScannerInConstruction

getConnection

getTableName

getTable

getRetries

getScannerTimeout

getConf

getScan

getPool

getPrimaryOperationTimeout

getCaching

getTimestamp

getMaxResultSize

checkScanStopRow

possiblyNextScanner

nextScanner

isAnyRPCcancelled

call

getScannerCallable

writeScanMetrics

next

getCacheSize

loadCache

doneWithRegion

getResultsToAddToCache

addToPartialResults

clearPartialResults

addResultsToList

close

createClosestRowBefore

renewLease

updateLastCellLoadedToCache

compare

filterLoadedCell