org.apache.kudu.client

Class 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.

Method Summary

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 RowResultIterator.next().

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 RowResultIterator.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.

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.

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>