KuduScanner

java.lang.Object
- org.apache.kudu.client.KuduScanner

All Implemented Interfaces:

Iterable<RowResult>
```
@InterfaceAudience.Public
 @InterfaceStability.Evolving
public class KuduScanner
extends Object
implements Iterable<RowResult>
```
Synchronous version of AsyncKuduScanner. Offers the same API but with blocking methods.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class KuduScanner.KuduScannerBuilder
A Builder class to build KuduScanner.

Nested Classes
Modifier and Type	Class and Description
`static class`	`KuduScanner.KuduScannerBuilder` A Builder class to build `KuduScanner`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`RowResultIterator`	`close()` Closes this scanner (don't forget to call this when you're done with it!).
`long`	`getBatchSizeBytes()` Returns the maximum number of bytes returned by the scanner, on each batch.
`boolean`	`getCacheBlocks()` Returns if this scanner was configured to cache data blocks or not.
`long`	`getLimit()` Returns the maximum number of rows that this scanner was configured to return.
`Schema`	`getProjectionSchema()` Returns the projection schema of this scanner.
`AsyncKuduScanner.ReadMode`	`getReadMode()` Returns the ReadMode for this scanner.
`ResourceMetrics`	`getResourceMetrics()` Returns the resource metrics of this scanner.
`long`	`getScanRequestTimeout()` Returns the current value of the scanner's scan request timeout.
`boolean`	`hasMoreRows()` Tells if the last rpc returned that there might be more rows to scan.
`boolean`	`isClosed()`
`KuduScannerIterator`	`iterator()`
`void`	`keepAlive()` Keep the current remote scanner alive.
`RowResultIterator`	`nextRows()` Scans a number of rows.
`void`	`setReuseRowResult(boolean reuseRowResult)` If set to true, the `RowResult` object returned by the `RowResultIterator` will be reused with each call to `Iterator.next()`.
`void`	`setRowDataFormat(AsyncKuduScanner.RowDataFormat rowDataFormat)` Optionally set expected row data format.
`boolean`	`startKeepAlivePeriodically(int keepAliveIntervalMS)` Keep the current remote scanner alive by sending keep-alive requests periodically.
`boolean`	`stopKeepAlivePeriodically()` Stop keeping the current remote scanner alive periodically.

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

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Method Detail
  - hasMoreRows
```
public boolean hasMoreRows()
```
    Tells if the last rpc returned that there might be more rows to scan.
    
    Returns:
    
    true if there might be more data to scan, else false
  - setReuseRowResult
```
public void setReuseRowResult(boolean reuseRowResult)
```
    If set to true, the RowResult object returned by the RowResultIterator will be reused with each call to Iterator.next(). This can be a useful optimization to reduce the number of objects created. Note: DO NOT use this if the RowResult is stored between calls to next(). Enabling this optimization means that a call to next() mutates the previously returned RowResult. Accessing the previously returned RowResult after a call to next(), by storing all RowResults in a collection and accessing them later for example, will lead to all of the stored RowResults being mutated as per the data in the last RowResult returned.
  - setRowDataFormat
```
public void setRowDataFormat(AsyncKuduScanner.RowDataFormat rowDataFormat)
```
    Optionally set expected row data format.
    
    Parameters:
    
    rowDataFormat - Row data format to be expected.
  - nextRows
```
public RowResultIterator nextRows()
                           throws KuduException
```
    Scans a number of rows.
    Once this method returns null once (which indicates that this Scanner is done scanning), calling it again leads to an undefined behavior.
    
    Returns:
    
    a list of rows.
    
    Throws:
    
    KuduException - if anything went wrong.
  - keepAlive
```
public final void keepAlive()
                     throws KuduException
```
    Keep the current remote scanner alive.
    Keep the current remote scanner alive on the Tablet server for an additional time-to-live. This is useful if the interval in between nextRows() calls is big enough that the remote scanner might be garbage collected. The scanner time-to-live can be configured on the tablet server via the --scanner_ttl_ms configuration flag and has a default of 60 seconds.
    This does not invalidate any previously fetched results.
    Note that an exception thrown by this method should not be taken as indication that the scan has failed. Subsequent calls to nextRows() might still be successful, particularly if the scanner is configured to be fault tolerant.
    
    Throws:
    
    KuduException - if anything went wrong.
  - startKeepAlivePeriodically
```
public final boolean startKeepAlivePeriodically(int keepAliveIntervalMS)
                                         throws KuduException
```
    Keep the current remote scanner alive by sending keep-alive requests periodically.
    startKeepAlivePeriodically() uses a timer to call keepAlive() periodically, which is defined by parameter keepAliveIntervalMS. It sends keep-alive requests to the server periodically using a separate thread. This is useful if the client takes long time to handle the fetched data before having the chance to call keepAlive(). This can be called after the scanner is opened and the timer can be stopped by calling stopKeepAlivePeriodically().
    
    Throws:
    
    KuduException - if anything went wrong.
    * @return true if starting keep-alive timer successfully.
  - stopKeepAlivePeriodically
```
public final boolean stopKeepAlivePeriodically()
```
    Stop keeping the current remote scanner alive periodically.
    This function stops to send keep-alive requests to the server periodically. After function startKeepAlivePeriodically is called, this function can be used to stop the keep-alive timer at any time. The timer will be stopped automatically after finishing scanning. But it can also be stopped manually by calling this function.
    
    Returns:
    
    true if stopping keep-alive timer successfully.
  - isClosed
```
public boolean isClosed()
```
    Returns:
    
    true if the scanner has been closed.
  - close
```
public RowResultIterator close()
                        throws KuduException
```
    Closes this scanner (don't forget to call this when you're done with it!).
    Closing a scanner already closed has no effect.
    
    Returns:
    
    a deferred object that indicates the completion of the request
    
    Throws:
    
    KuduException - if anything went wrong.
  - getLimit
```
public long getLimit()
```
    Returns the maximum number of rows that this scanner was configured to return.
    
    Returns:
    
    a long representing the maximum number of rows that can be returned
  - getCacheBlocks
```
public boolean getCacheBlocks()
```
    Returns if this scanner was configured to cache data blocks or not.
    
    Returns:
    
    true if this scanner will cache blocks, else else.
  - getBatchSizeBytes
```
public long getBatchSizeBytes()
```
    Returns the maximum number of bytes returned by the scanner, on each batch.
    
    Returns:
    
    a long representing the maximum number of bytes that a scanner can receive at once from a tablet server
  - getReadMode
```
public AsyncKuduScanner.ReadMode getReadMode()
```
    Returns the ReadMode for this scanner.
    
    Returns:
    
    the configured read mode for this scanner
  - getProjectionSchema
```
public Schema getProjectionSchema()
```
    Returns the projection schema of this scanner. If specific columns were not specified during scanner creation, the table schema is returned.
    
    Returns:
    
    the projection schema for this scanner
  - getResourceMetrics
```
public ResourceMetrics getResourceMetrics()
```
    Returns the resource metrics of this scanner.
    
    Returns:
    
    the resource metrics for this scanner
  - getScanRequestTimeout
```
public long getScanRequestTimeout()
```
    Returns the current value of the scanner's scan request timeout.
    
    Returns:
    
    the timeout value, in milliseconds
  - iterator
```
public KuduScannerIterator iterator()
```
    Specified by:
    
    iterator in interface Iterable<RowResult>

Class KuduScanner

Nested Class Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Method Detail

hasMoreRows

setReuseRowResult

setRowDataFormat

nextRows

keepAlive

startKeepAlivePeriodically

stopKeepAlivePeriodically

isClosed

close

getLimit

getCacheBlocks

getBatchSizeBytes

getReadMode

getProjectionSchema

getResourceMetrics

getScanRequestTimeout

iterator