Package com.apple.foundationdb

Interface ReadTransaction

    • Field Detail

      • ROW_LIMIT_UNLIMITED

        static final int ROW_LIMIT_UNLIMITED
        When passed to a getRange() call that takes a limit parameter, indicates that the query should return unlimited rows.
        See Also:
        Constant Field Values

    • Method Detail

      • isSnapshot

        boolean isSnapshot()
        Gets whether this transaction is a snapshot view of the database. In other words, this returns whether read conflict ranges are omitted for any reads done through this ReadTransaction.
        For more information about how to use snapshot reads correctly, see Using snapshot reads.
        Returns:
        whether this is a snapshot view of the database with relaxed isolation properties
        See Also:
        snapshot()

      • snapshot

        ReadTransaction snapshot()
        Return a special-purpose, read-only view of the database. Reads done through this interface are known as "snapshot reads". Snapshot reads selectively relax FoundationDB's isolation property, reducing Transaction conflicts but making reasoning about concurrency harder.

        For more information about how to use snapshot reads correctly, see Using snapshot reads.
        Returns:
        a read-only view of this ReadTransaction with relaxed isolation properties

      • getReadVersion

        java.util.concurrent.CompletableFuture<java.lang.Long> getReadVersion()
        Gets the version at which the reads for this Transaction will access the database.
        Returns:
        the version for database reads

      • setReadVersion

        void setReadVersion​(long version)
        Directly sets the version of the database at which to execute reads. The normal operation of a transaction is to determine an appropriately recent version; this call overrides that behavior. If the version is set too far in the past, transaction_too_old errors will be thrown from read operations. Infrequently used.
        Parameters:
        version - the version at which to read from the database

      • addReadConflictRangeIfNotSnapshot

        boolean addReadConflictRangeIfNotSnapshot​(byte[] keyBegin,
                                          byte[] keyEnd)
        Adds the read conflict range that this ReadTransaction would have added as if it had read the given key range. If this is a snapshot view of the database, this will not add the conflict range. This mirrors how reading a range through a snapshot view of the database does not add a conflict range for the read keys.
        Parameters:
        keyBegin - the first key in the range (inclusive)
        keyEnd - the last key in the range (exclusive)
        Returns:
        true if the read conflict range was added and false otherwise
        See Also:
        Transaction.addReadConflictRange(byte[], byte[])

      • addReadConflictKeyIfNotSnapshot

        boolean addReadConflictKeyIfNotSnapshot​(byte[] key)
        Adds the read conflict range that this ReadTransaction would have added as if it had read the given key. If this is a snapshot view of the database, this will not add the conflict range. This mirrors how reading a key through a snapshot view of the database does not add a conflict range for the read key.
        Parameters:
        key - the key to add to the read conflict range set (it this is not a snapshot view of the database)
        Returns:
        true if the read conflict key was added and false otherwise
        See Also:
        Transaction.addReadConflictKey(byte[])

      • get

        java.util.concurrent.CompletableFuture<byte[]> get​(byte[] key)
        Gets a value from the database. The call will return null if the key is not present in the database.
        Parameters:
        key - the key whose value to fetch from the database
        Returns:
        a CompletableFuture which will be set to the value corresponding to the key or to null if the key does not exist.

      • getKey

        java.util.concurrent.CompletableFuture<byte[]> getKey​(KeySelector selector)
        Returns the key referenced by the specified KeySelector. By default, the key is cached for the duration of the transaction, providing a potential performance benefit. However, the value of the key is also retrieved, using network bandwidth. Invoking setReadYourWritesDisable will avoid both the caching and the increased network bandwidth.
        Parameters:
        selector - the relative key location to resolve
        Returns:
        a CompletableFuture which will be set to an absolute database key
        See Also:
        KeySelector

      • getRange

        AsyncIterable<KeyValue> getRange​(KeySelector begin,
                                 KeySelector end)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by KeySelectors, with the begin KeySelector inclusive and the end KeySelector exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(KeySelector begin,
                                 KeySelector end,
                                 int limit)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by KeySelectors, with the begin KeySelector inclusive and the end KeySelector exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results.
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(KeySelector begin,
                                 KeySelector end,
                                 int limit,
                                 boolean reverse)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by KeySelectors, with the begin KeySelector inclusive and the end KeySelector exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results. If reverse is true rows will be limited starting at the end of the range.
        reverse - return results starting at the end of the range in reverse order. Reading ranges in reverse is supported natively by the database and should have minimal extra cost.
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(KeySelector begin,
                                 KeySelector end,
                                 int limit,
                                 boolean reverse,
                                 StreamingMode mode)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by KeySelectors, with the begin KeySelector inclusive and the end KeySelector exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results. If reverse is true rows will be limited starting at the end of the range.
        reverse - return results starting at the end of the range in reverse order. Reading ranges in reverse is supported natively by the database and should have minimal extra cost.
        mode - provide a hint about how the results are to be used. This can provide speed improvements or efficiency gains based on the caller's knowledge of the upcoming access pattern.

        When converting the result of this query to a list using AsyncIterable.asList() with the ITERATOR streaming mode, the query is automatically modified to fetch results in larger batches. This is done because it is known in advance that the AsyncIterable.asList() function will fetch all results in the range. If a limit is specified, the EXACT streaming mode will be used, and otherwise it will use WANT_ALL. To achieve comparable performance when iterating over an entire range without using AsyncIterable.asList(), the same streaming mode would need to be used.

        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(byte[] begin,
                                 byte[] end)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(byte[] begin,
                                 byte[] end,
                                 int limit)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results.
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(byte[] begin,
                                 byte[] end,
                                 int limit,
                                 boolean reverse)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results. If reverse is true rows will be limited starting at the end of the range.
        reverse - return results starting at the end of the range in reverse order. Reading ranges in reverse is supported natively by the database and should have minimal extra cost.
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(byte[] begin,
                                 byte[] end,
                                 int limit,
                                 boolean reverse,
                                 StreamingMode mode)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results. If reverse is true rows will be limited starting at the end of the range.
        reverse - return results starting at the end of the range in reverse order. Reading ranges in reverse is supported natively by the database and should have minimal extra cost.
        mode - provide a hint about how the results are to be used. This can provide speed improvements or efficiency gains based on the caller's knowledge of the upcoming access pattern.

        When converting the result of this query to a list using AsyncIterable.asList() with the ITERATOR streaming mode, the query is automatically modified to fetch results in larger batches. This is done because it is known in advance that the AsyncIterable.asList() function will fetch all results in the range. If a limit is specified, the EXACT streaming mode will be used, and otherwise it will use WANT_ALL. To achieve comparable performance when iterating over an entire range without using AsyncIterable.asList(), the same streaming mode would need to be used.

        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(Range range)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive. Ranges are returned from calls to Tuple.range() and Range.startsWith(byte[]).

        Note: users of older version of the API should replace old calls to getRangeStartsWith( k ) with getRange(Range.startsWith( k ))
        Parameters:
        range - the range of keys to return
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(Range range,
                                 int limit)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive. Ranges are returned from calls to Tuple.range() and Range.startsWith(byte[]).

        Note: users of older version of the API should replace old calls to getRangeStartsWith( k ) with getRange(Range.startsWith( k ))
        Parameters:
        range - the range of keys to return
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results.
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(Range range,
                                 int limit,
                                 boolean reverse)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive. Ranges are returned from calls to Tuple.range() and Range.startsWith(byte[]).

        Note: users of older version of the API should replace old calls to getRangeStartsWith( k ) with getRange(Range.startsWith( k ))
        Parameters:
        range - the range of keys to return
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results. If reverse is true rows will be limited starting at the end of the range.
        reverse - return results starting at the end of the range in reverse order. Reading ranges in reverse is supported natively by the database and should have minimal extra cost.
        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getRange

        AsyncIterable<KeyValue> getRange​(Range range,
                                 int limit,
                                 boolean reverse,
                                 StreamingMode mode)
        Gets an ordered range of keys and values from the database. The begin and end keys are specified by byte[] arrays, with the begin key inclusive and the end key exclusive. Ranges are returned from calls to Tuple.range() and Range.startsWith(byte[]).

        Note: users of older version of the API should replace old calls to getRangeStartsWith( k ) with getRange(Range.startsWith( k ))
        Parameters:
        range - the range of keys to return
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results. If reverse is true rows will be limited starting at the end of the range.
        reverse - return results starting at the end of the range in reverse order. Reading ranges in reverse is supported natively by the database and should have minimal extra cost.
        mode - provide a hint about how the results are to be used. This can provide speed improvements or efficiency gains based on the caller's knowledge of the upcoming access pattern.

        When converting the result of this query to a list using AsyncIterable.asList() with the ITERATOR streaming mode, the query is automatically modified to fetch results in larger batches. This is done because it is known in advance that the AsyncIterable.asList() function will fetch all results in the range. If a limit is specified, the EXACT streaming mode will be used, and otherwise it will use WANT_ALL. To achieve comparable performance when iterating over an entire range without using AsyncIterable.asList(), the same streaming mode would need to be used.

        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getMappedRange

        AsyncIterable<MappedKeyValue> getMappedRange​(KeySelector begin,
                                             KeySelector end,
                                             byte[] mapper,
                                             int limit,
                                             boolean reverse,
                                             StreamingMode mode)
        WARNING: This feature is considered experimental at this time. It is only allowed when using snapshot isolation AND disabling read-your-writes.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        mapper - TODO
        limit - the maximum number of results to return. Limits results to the first keys in the range. Pass ROW_LIMIT_UNLIMITED if this query should not limit the number of results. If reverse is true rows will be limited starting at the end of the range.
        reverse - return results starting at the end of the range in reverse order. Reading ranges in reverse is supported natively by the database and should have minimal extra cost.
        mode - provide a hint about how the results are to be used. This can provide speed improvements or efficiency gains based on the caller's knowledge of the upcoming access pattern.

        When converting the result of this query to a list using AsyncIterable.asList() with the ITERATOR streaming mode, the query is automatically modified to fetch results in larger batches. This is done because it is known in advance that the AsyncIterable.asList() function will fetch all results in the range. If a limit is specified, the EXACT streaming mode will be used, and otherwise it will use WANT_ALL. To achieve comparable performance when iterating over an entire range without using AsyncIterable.asList(), the same streaming mode would need to be used.

        Returns:
        a handle to access the results of the asynchronous call
        See Also:
        KeySelector, AsyncIterator

      • getEstimatedRangeSizeBytes

        java.util.concurrent.CompletableFuture<java.lang.Long> getEstimatedRangeSizeBytes​(byte[] begin,
                                                                                  byte[] end)
        Gets an estimate for the number of bytes stored in the given range. Note: the estimated size is calculated based on the sampling done by FDB server. The sampling algorithm works roughly in this way: the larger the key-value pair is, the more likely it would be sampled and the more accurate its sampled size would be. And due to that reason it is recommended to use this API to query against large ranges for accuracy considerations. For a rough reference, if the returned size is larger than 3MB, one can consider the size to be accurate.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        Returns:
        a handle to access the results of the asynchronous call

      • getEstimatedRangeSizeBytes

        java.util.concurrent.CompletableFuture<java.lang.Long> getEstimatedRangeSizeBytes​(Range range)
        Gets an estimate for the number of bytes stored in the given range. Note: the estimated size is calculated based on the sampling done by FDB server. The sampling algorithm works roughly in this way: the larger the key-value pair is, the more likely it would be sampled and the more accurate its sampled size would be. And due to that reason it is recommended to use this API to query against large ranges for accuracy considerations. For a rough reference, if the returned size is larger than 3MB, one can consider the size to be accurate.
        Parameters:
        range - the range of the keys
        Returns:
        a handle to access the results of the asynchronous call

      • getRangeSplitPoints

        java.util.concurrent.CompletableFuture<KeyArrayResult> getRangeSplitPoints​(byte[] begin,
                                                                           byte[] end,
                                                                           long chunkSize)
        Gets a list of keys that can split the given range into (roughly) equally sized chunks based on chunkSize. Note: the returned split points contain the start key and end key of the given range.
        Parameters:
        begin - the beginning of the range (inclusive)
        end - the end of the range (exclusive)
        Returns:
        a handle to access the results of the asynchronous call

      • getRangeSplitPoints

        java.util.concurrent.CompletableFuture<KeyArrayResult> getRangeSplitPoints​(Range range,
                                                                           long chunkSize)
        Gets a list of keys that can split the given range into (roughly) equally sized chunks based on chunkSize Note: the returned split points contain the start key and end key of the given range.
        Parameters:
        range - the range of the keys
        Returns:
        a handle to access the results of the asynchronous call

      • options

        TransactionOptions options()
        Returns a set of options that can be set on a Transaction
        Returns:
        a set of transaction-specific options affecting this Transaction