Merge pull request #155 from seanpmorgan/reversed-scan

Adding reversed scanner, and new compat mode 0.98

happybase/connection.py

@@ -20,7 +20,7 @@
 
 STRING_OR_BINARY = (six.binary_type, six.text_type)
 
-COMPAT_MODES = ('0.90', '0.92', '0.94', '0.96')
+COMPAT_MODES = ('0.90', '0.92', '0.94', '0.96', '0.98')
 THRIFT_TRANSPORTS = dict(
     buffered=TBufferedTransport,
     framed=TFramedTransport,
@@ -33,7 +33,7 @@
 DEFAULT_HOST = 'localhost'
 DEFAULT_PORT = 9090
 DEFAULT_TRANSPORT = 'buffered'
-DEFAULT_COMPAT = '0.96'
+DEFAULT_COMPAT = '0.98'
 DEFAULT_PROTOCOL = 'binary'
 
 

happybase/table.py

@@ -222,7 +222,7 @@ def cells(self, row, column, versions=None, timestamp=None,
     def scan(self, row_start=None, row_stop=None, row_prefix=None,
              columns=None, filter=None, timestamp=None,
              include_timestamp=False, batch_size=1000, scan_batching=None,
-             limit=None, sorted_columns=False):
+             limit=None, sorted_columns=False, reverse=False):
         """Create a scanner for data in the table.
 
         This method returns an iterable that can be used for looping over the
@@ -268,6 +268,11 @@ def scan(self, row_start=None, row_stop=None, row_prefix=None,
         by this scanner will be retrieved in sorted order, and the data
         will be stored in `OrderedDict` instances.
 
+        If `reverse` is `True`, the scanner will perform the scan in reverse.
+        This means that `row_start` must be lexicographically after `row_stop`.
+        Note that the start of the range is inclusive, while the end is
+        exclusive just as in the forward scan.
+
         **Compatibility notes:**
 
         * The `filter` argument is only available when using HBase 0.92
@@ -277,6 +282,12 @@ def scan(self, row_start=None, row_stop=None, row_prefix=None,
         * The `sorted_columns` argument is only available when using
           HBase 0.96 (or up).
 
+        * The `reverse` argument is only available when using HBase 0.98
+          (or up).
+
+        .. versionadded:: TODO
+           `reverse` argument
+
         .. versionadded:: 0.8
            `sorted_columns` argument
 
@@ -294,6 +305,7 @@ def scan(self, row_start=None, row_stop=None, row_prefix=None,
         :param bool scan_batching: server-side scan batching (optional)
         :param int limit: max number of rows to return
         :param bool sorted_columns: whether to return sorted columns
+        :param bool reverse: whether to perform scan in reverse
 
         :return: generator yielding the rows matching the scan
         :rtype: iterable of `(row_key, row_data)` tuples
@@ -311,14 +323,22 @@ def scan(self, row_start=None, row_stop=None, row_prefix=None,
             raise NotImplementedError(
                 "'sorted_columns' is only supported in HBase >= 0.96")
 
+        if reverse and self.connection.compat < '0.98':
+            raise NotImplementedError(
+                "'reverse' is only supported in HBase >= 0.98")
+
         if row_prefix is not None:
             if row_start is not None or row_stop is not None:
                 raise TypeError(
                     "'row_prefix' cannot be combined with 'row_start' "
                     "or 'row_stop'")
 
-            row_start = row_prefix
-            row_stop = bytes_increment(row_prefix)
+            if reverse:
+                row_start = bytes_increment(row_prefix)
+                row_stop = row_prefix
+            else:
+                row_start = row_prefix
+                row_stop = bytes_increment(row_prefix)
 
         if row_start is None:
             row_start = ''
@@ -376,6 +396,7 @@ def scan(self, row_start=None, row_stop=None, row_prefix=None,
                 filterString=filter,
                 batchSize=scan_batching,
                 sortColumns=sorted_columns,
+                reversed=reverse,
             )
             scan_id = self.connection.client.scannerOpenWithScan(
                 self.name, scan, {})

tests/test_api.py

@@ -27,7 +27,7 @@
 
 HAPPYBASE_HOST = os.environ.get('HAPPYBASE_HOST')
 HAPPYBASE_PORT = os.environ.get('HAPPYBASE_PORT')
-HAPPYBASE_COMPAT = os.environ.get('HAPPYBASE_COMPAT', '0.96')
+HAPPYBASE_COMPAT = os.environ.get('HAPPYBASE_COMPAT', '0.98')
 HAPPYBASE_TRANSPORT = os.environ.get('HAPPYBASE_TRANSPORT', 'buffered')
 KEEP_TABLE = ('HAPPYBASE_NO_CLEANUP' in os.environ)
 
@@ -446,6 +446,34 @@ def test_scan_sorting():
         list(row.items()))
 
 
+def test_scan_reverse():
+
+    if connection.compat < '0.98':
+        with assert_raises(NotImplementedError):
+            list(table.scan(reverse=True))
+        return
+
+    with table.batch() as b:
+        for i in range(2000):
+            b.put(('row-scan-reverse-%04d' % i).encode('ascii'),
+                  {b'cf1:col1': b'v1',
+                   b'cf1:col2': b'v2'})
+
+    scan = table.scan(row_prefix=b'row-scan-reverse', reverse=True)
+    assert_equal(2000, len(list(scan)))
+
+    scan = table.scan(limit=10, reverse=True)
+    assert_equal(10, len(list(scan)))
+
+    scan = table.scan(row_start=b'row-scan-reverse-1999',
+                      row_stop=b'row-scan-reverse-0000', reverse=True)
+    key, data = next(scan)
+    assert_equal(b'row-scan-reverse-1999', key)
+
+    key, data = list(scan)[-1]
+    assert_equal(b'row-scan-reverse-0001', key)
+
+
 def test_scan_filter_and_batch_size():
     # See issue #54 and #56
     filter = b"SingleColumnValueFilter ('cf1', 'qual1', =, 'binary:val1')"