use farey function
This commit is contained in:
Erik Johnston
parent
ca11acf388
commit
1205362f1d
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@ -21,6 +21,7 @@ from gmpy2 import mpq as Fraction
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from fractions import Fraction as FractionPy
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from synapse.storage._base import SQLBaseStore
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from synapse.storage.engines import PostgresEngine
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from synapse.util.katriel_bodlaender import OrderedListStore
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import synapse.metrics
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@ -91,12 +92,13 @@ class ChunkDBOrderedListStore(OrderedListStore):
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this.
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"""
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def __init__(self,
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txn, room_id, clock,
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txn, room_id, clock, database_engine,
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rebalance_max_denominator=100,
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max_denominator=100000):
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self.txn = txn
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self.room_id = room_id
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self.clock = clock
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self.database_engine = database_engine
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self.rebalance_md = rebalance_max_denominator
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self.max_denominator = max_denominator
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@ -390,69 +392,43 @@ class ChunkDBOrderedListStore(OrderedListStore):
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logger.info("Rebalancing room %s, chunk %s", self.room_id, node_id)
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old_order = self._get_order(node_id)
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new_order = FractionPy(
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int(old_order.numerator),
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int(old_order.denominator),
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).limit_denominator(
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self.rebalance_md,
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)
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new_order = Fraction(new_order.numerator, new_order.denominator)
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if new_order < old_order:
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new_order += Fraction(1, new_order.denominator)
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count_nodes = [node_id]
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next_id = node_id
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while True:
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next_id = self.get_next(next_id)
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a, b, c, d = find_farey_terms(old_order, self.rebalance_md)
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n = max(b, d)
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if not next_id:
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max_order = None
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break
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count_nodes.append(next_id)
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max_order = self._get_order(next_id)
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if len(count_nodes) < self.rebalance_md * (max_order - new_order):
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break
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if len(count_nodes) == 1:
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orders = [new_order]
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if max_order:
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orders = stern_brocot_range(len(count_nodes), new_order, max_order)
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orders.sort(reverse=True)
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else:
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orders = [
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Fraction(int(math.ceil(new_order)) + i, 1)
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for i in xrange(0, len(count_nodes))
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]
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orders.reverse()
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assert len(count_nodes) == len(orders)
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next_id = node_id
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prev_order = old_order
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while orders:
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order = orders.pop()
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if max_order:
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assert old_order <= new_order <= max_order
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else:
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assert old_order <= new_order
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assert prev_order < order
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SQLBaseStore._simple_update_txn(
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self.txn,
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table="chunk_linearized",
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keyvalues={"chunk_id": next_id},
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updatevalues={
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"numerator": int(order.numerator),
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"denominator": int(order.denominator),
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},
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with_sql = """
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WITH RECURSIVE chunks (chunk_id, next, n, a, b, c, d) AS (
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SELECT chunk_id, next_chunk_id, ?, ?, ?, ?, ?
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FROM chunk_linearized WHERE chunk_id = ?
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UNION ALL
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SELECT n.chunk_id, n.next_chunk_id, n, c, d, ((n + b) / d) * c - a, ((n + b) / d) * d - b
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FROM chunks AS c
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INNER JOIN chunk_linearized AS l ON l.chunk_id = c.chunk_id
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INNER JOIN chunk_linearized AS n ON n.chunk_id = l.next_chunk_id
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WHERE c * 1.0 / d > n.numerator * 1.0 / n.denominator
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)
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"""
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next_id = self.get_next(next_id)
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if isinstance(self.database_engine, PostgresEngine):
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sql = with_sql + """
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UPDATE chunk_linearized AS l
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SET numerator = a, denominator = b
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FROM chunks AS c
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WHERE c.chunk_id = l.chunk_id
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"""
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else:
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sql = with_sql + """
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UPDATE chunk_linearized
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SET (numerator, denominator) = (
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SELECT a, b FROM chunks
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WHERE chunks.chunk_id = chunk_linearized.chunk_id
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)
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WHERE chunk_id in (SELECT chunk_id FROM chunks)
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"""
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self.txn.execute(sql, (
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n, a, b, c, d, node_id
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))
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rebalance_counter.inc()
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@ -512,7 +488,7 @@ def stern_brocot_single(min_frac, max_frac):
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def stern_brocot_range_depth(min_frac, max_denom):
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assert 0 < min_frac
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states = stern_brocot_single(min_frac)
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states = stern_brocot_singless(min_frac)
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while len(states):
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a, b, c, d = states.pop()
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@ -534,22 +510,51 @@ def stern_brocot_range_depth(min_frac, max_denom):
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def stern_brocot_single(min_frac):
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def stern_brocot_state(min_frac, target_d):
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assert 0 <= min_frac
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states = []
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a, b, c, d = 0, 1, 1, 0
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states.append((a, b, c, d))
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while True:
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f = Fraction(a + c, b + d)
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if b + d >= target_d:
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return a + c, b + d, c, d
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if f < min_frac:
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a, b, c, d = a + c, b + d, c, d
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elif f == min_frac:
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return states
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return a + c, b + d, c, d
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else:
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a, b, c, d = a, b, a + c, b + d
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states.append((a, b, c, d))
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def find_farey_terms(min_frac, max_denom):
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states = deque([(0, 1, 1, 0)])
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while True:
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a, b, c, d = states.popleft()
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left = a / float(b)
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mid = (a + c) / float(b + d)
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right = c / float(d) if d > 0 else None
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if min_frac < left:
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if b >= max_denom or d >= max_denom:
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return a, b, c, d
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if b + d >= max_denom:
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return a + c, b + d, c, d
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states.append((a, b, a + c, b + d))
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elif min_frac < mid:
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if b + d >= max_denom:
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return a + c, b + d, c, d
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states.append((a, b, a + c, b + d))
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states.append((a + c, b + d, c, d))
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elif right is None or min_frac < right:
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states.append((a + c, b + d, c, d))
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else:
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states.append((a + c, b + d, c, d))
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@ -44,7 +44,9 @@ class ChunkLinearizerStoreTestCase(tests.unittest.TestCase):
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def test_txn(txn):
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table = ChunkDBOrderedListStore(
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txn, room_id, self.clock, 5, 100,
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txn, room_id, self.clock,
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self.store.database_engine,
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5, 100,
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)
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table.add_node("A")
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@ -71,7 +73,9 @@ class ChunkLinearizerStoreTestCase(tests.unittest.TestCase):
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def test_txn(txn):
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table = ChunkDBOrderedListStore(
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txn, room_id, self.clock, 5, 100,
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txn, room_id, self.clock,
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self.store.database_engine,
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5, 100,
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)
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nodes = [(i, "node_%d" % (i,)) for i in xrange(1, 1000)]
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@ -116,7 +120,9 @@ class ChunkLinearizerStoreTestCase(tests.unittest.TestCase):
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def test_txn(txn):
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table = ChunkDBOrderedListStore(
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txn, room_id, self.clock, 5, 1000,
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txn, room_id, self.clock,
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self.store.database_engine,
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5, 1000,
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)
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table.add_node("a")
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@ -152,7 +158,9 @@ class ChunkLinearizerStoreTestCase(tests.unittest.TestCase):
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def test_txn(txn):
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table = ChunkDBOrderedListStore(
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txn, room_id, self.clock, 5, 100,
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txn, room_id, self.clock,
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self.store.database_engine,
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5, 100,
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)
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table.add_node("a")
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@ -193,7 +201,9 @@ class ChunkLinearizerStoreTestCase(tests.unittest.TestCase):
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def test_txn(txn):
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table = ChunkDBOrderedListStore(
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txn, room_id, self.clock, 5, 100,
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txn, room_id, self.clock,
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self.store.database_engine,
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5, 100,
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)
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table.add_node("A")
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@ -216,7 +226,9 @@ class ChunkLinearizerStoreTestCase(tests.unittest.TestCase):
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def test_txn(txn):
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table = ChunkDBOrderedListStore(
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txn, room_id, self.clock, 5, 100,
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txn, room_id, self.clock,
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self.store.database_engine,
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5, 100,
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)
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table.add_node("A")
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