Class KeyValueCursor
- java.lang.Object
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- com.apple.foundationdb.record.cursors.AsyncIteratorCursor<KeyValue>
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- com.apple.foundationdb.record.provider.foundationdb.KeyValueCursor
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- All Implemented Interfaces:
BaseCursor<KeyValue>
,RecordCursor<KeyValue>
,AutoCloseable
,Iterator<KeyValue>
@API(MAINTAINED) public class KeyValueCursor extends AsyncIteratorCursor<KeyValue> implements BaseCursor<KeyValue>
The basic cursor for scanning ranges of the FDB database.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
KeyValueCursor.Builder
A builder forKeyValueCursor
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Nested classes/interfaces inherited from interface com.apple.foundationdb.record.RecordCursor
RecordCursor.NoNextReason
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Field Summary
Fields Modifier and Type Field Description protected Executor
executor
protected CompletableFuture<Boolean>
hasNextFuture
protected C
iterator
protected boolean
mayGetContinuation
protected RecordCursorResult<T>
nextResult
protected int
valuesSeen
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description boolean
accept(RecordCursorVisitor visitor)
Accept a visit from hierarchical visitor, which implementsRecordCursorVisitor
.void
close()
protected RecordCursorResult<T>
computeNextResult(boolean hasNext)
byte[]
getContinuation()
Deprecated.Executor
getExecutor()
RecordCursorResult<KeyValue>
getNext()
Get the next result from this cursor.RecordCursor.NoNextReason
getNoNextReason()
Deprecated.T
next()
Deprecated.CompletableFuture<Boolean>
onHasNext()
Deprecated.CompletableFuture<RecordCursorResult<KeyValue>>
onNext()
Asynchronously return the next result from this cursor.-
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface java.util.Iterator
forEachRemaining, remove
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Methods inherited from interface com.apple.foundationdb.record.RecordCursor
accept, asIterator, asList, close, filter, filterAsync, filterAsyncInstrumented, filterAsyncInstrumented, filterInstrumented, filterInstrumented, first, flatMapPipelined, forEach, forEachAsync, forEachResult, forEachResultAsync, getContinuation, getCount, getExecutor, getNoNextReason, hasNext, limitRowsTo, limitTo, map, mapEffect, mapEffect, mapPipelined, next, onHasNext, orElse, reduce, skip, skipThenLimit
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Field Detail
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valuesSeen
protected int valuesSeen
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hasNextFuture
@Nullable protected CompletableFuture<Boolean> hasNextFuture
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nextResult
@Nullable protected RecordCursorResult<T> nextResult
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mayGetContinuation
protected boolean mayGetContinuation
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Method Detail
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onNext
@Nonnull public CompletableFuture<RecordCursorResult<KeyValue>> onNext()
Description copied from interface:RecordCursor
Asynchronously return the next result from this cursor. When complete, the future will contain aRecordCursorResult
, which represents exactly one of the following:-
The next object of type
T
produced by the cursor. In addition to the next record, this result includes aRecordCursorContinuation
that can be used to continue the cursor after the last record returned. The returned continuation is guaranteed not to be an "end continuation" representing the end of the cursor: specifically,RecordCursorContinuation.isEnd()
is alwaysfalse
on the returned continuation. -
The fact that the cursor is stopped and cannot produce another record and a
RecordCursor.NoNextReason
that explains why no record could be produced. The result include a continuation that can be used to continue the cursor after the last record returned. If the result'sNoNextReason
is anything other thanRecordCursor.NoNextReason.SOURCE_EXHAUSTED
, the returned continuation must not be an end continuation. Conversely, if the result'sNoNextReason
isSOURCE_EXHAUSTED
, then the returned continuation must be an an "end continuation".
RecordCursorContinuation
can be serialized to an opaque byte array usingRecordCursorContinuation.toBytes()
. This can be passed back into a new cursor of the same type, with all other parameters remaining the same.- Specified by:
onNext
in interfaceRecordCursor<KeyValue>
- Overrides:
onNext
in classAsyncIteratorCursor<KeyValue>
- Returns:
- a future for the next result from this cursor representing either the next record or an indication of why the cursor stopped
- See Also:
RecordCursorResult
,RecordCursorContinuation
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The next object of type
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getNext
@Nonnull public RecordCursorResult<KeyValue> getNext()
Description copied from interface:RecordCursor
Get the next result from this cursor. In many cases, this is a blocking operation and should not be called within asynchronous contexts. The non-blocking version of this function,RecordCursor.onNext()
, should be preferred in such circumstances.- Specified by:
getNext
in interfaceRecordCursor<KeyValue>
- Returns:
- the next result from this cursor representing either the next record or an indication of why the cursor stopped
- See Also:
RecordCursor.onNext()
,RecordCursorResult
,RecordCursorContinuation
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computeNextResult
protected RecordCursorResult<T> computeNextResult(boolean hasNext)
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onHasNext
@Nonnull @Deprecated @API(DEPRECATED) public CompletableFuture<Boolean> onHasNext()
Deprecated.Description copied from interface:RecordCursor
Asynchronously check whether there are more records available from the cursor.- Specified by:
onHasNext
in interfaceRecordCursor<T>
- Returns:
- a future that when complete will hold
true
ifRecordCursor.next()
would return a record. - See Also:
AsyncIterator.onHasNext()
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next
@Nullable @Deprecated @API(DEPRECATED) public T next()
Deprecated.Description copied from interface:RecordCursor
Return the next value.
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getContinuation
@Nullable @Deprecated @API(DEPRECATED) public byte[] getContinuation()
Deprecated.Description copied from interface:RecordCursor
Get a byte string that can be used to continue a query after the last record returned.- Specified by:
getContinuation
in interfaceRecordCursor<T>
- Returns:
- opaque byte array denoting where the cursor should pick up. This can be passed back into a new
cursor of the same type, with all other parameters remaining the same.
Returns
null
if the underlying source is completely exhausted, independent of any limit passed to the cursor creator. Since such creators generally acceptnull
to mean no continuation, that is, start from the beginning, one must check fornull
fromgetContinuation
to keep from starting over. Result is not always defined if called beforeonHasNext
or beforenext
afteronHasNext
has returnedtrue
. That is, a continuation is only guaranteed when called "between" records from awhile (hasNext) next
loop or after its end.
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getNoNextReason
@Nonnull @Deprecated @API(DEPRECATED) public RecordCursor.NoNextReason getNoNextReason()
Deprecated.Description copied from interface:RecordCursor
Get the reason that the cursor has reached the end and returnedfalse
forRecordCursor.hasNext()
. IfhasNext
was not called or returnedtrue
last time, the result is undefined and may be an exception.- Specified by:
getNoNextReason
in interfaceRecordCursor<T>
- Returns:
- the reason that the cursor stopped
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close
public void close()
- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceRecordCursor<T>
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getExecutor
@Nonnull public Executor getExecutor()
- Specified by:
getExecutor
in interfaceRecordCursor<T>
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accept
public boolean accept(@Nonnull RecordCursorVisitor visitor)
Description copied from interface:RecordCursor
Accept a visit from hierarchical visitor, which implementsRecordCursorVisitor
. By contract, implementations of this method must return the value ofvisitor.visitLeave(this)
, which determines whether or not subsequent siblings of this cursor should be visited.- Specified by:
accept
in interfaceRecordCursor<T>
- Parameters:
visitor
- a hierarchical visitor- Returns:
true
if the subsequent siblings of thecursor
should be visited, andfalse
otherwise
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