Better batching with timelock (#3305)

* Better batching with timelock

Internally we were seeing that atm it takes about 2.5 seconds to delete
1k things. This is almost surely exclusively due to the overhead of
calling timelock once per cell.

* better releasenots

* comment

* fix compile

atlasdb-cassandra/src/main/java/com/palantir/atlasdb/keyvalue/cassandra/CassandraKeyValueServiceImpl.java

@@ -1757,18 +1757,33 @@ public void deleteRange(final TableReference tableRef, final RangeRequest range)
     @Override
     public void deleteAllTimestamps(TableReference tableRef, Map<Cell, Long> maxTimestampExclusiveByCell,
             boolean deleteSentinels) {
+        if (maxTimestampExclusiveByCell.isEmpty()) {
+            return;
+        }
+
         Map<InetSocketAddress, Map<Cell, Long>> keysByHost = HostPartitioner.partitionMapByHost(
                 clientPool, maxTimestampExclusiveByCell.entrySet());
+
+        // this is required by the interface of the CassandraMutationTimestampProvider, although it exists for tests
+        long maxTimestampForAllCells = maxTimestampExclusiveByCell.values().stream().mapToLong(x -> x).max().getAsLong();
+        long rangeTombstoneCassandraTimestamp =
+                mutationTimestampProvider.getRangeTombstoneTimestamp(maxTimestampForAllCells);
         for (Map.Entry<InetSocketAddress, Map<Cell, Long>> entry : keysByHost.entrySet()) {
-            deleteAllTimestampsOnSingleHost(tableRef, entry.getKey(), entry.getValue(), deleteSentinels);
+            deleteAllTimestampsOnSingleHost(
+                    tableRef,
+                    entry.getKey(),
+                    entry.getValue(),
+                    deleteSentinels,
+                    rangeTombstoneCassandraTimestamp);
         }
     }
 
     public void deleteAllTimestampsOnSingleHost(
             TableReference tableRef,
             InetSocketAddress host,
             Map<Cell, Long> maxTimestampExclusiveByCell,
-            boolean deleteSentinels) {
+            boolean deleteSentinels,
+            long rangeTombstoneCassandraTs) {
         if (maxTimestampExclusiveByCell.isEmpty()) {
             return;
         }
@@ -1778,7 +1793,8 @@ public void deleteAllTimestampsOnSingleHost(
 
                 @Override
                 public Void apply(CassandraClient client) throws Exception {
-                    insertRangeTombstones(client, maxTimestampExclusiveByCell, tableRef, deleteSentinels);
+                    insertRangeTombstones(client, maxTimestampExclusiveByCell, tableRef,
+                            deleteSentinels, rangeTombstoneCassandraTs);
                     return null;
                 }
 
@@ -1797,11 +1813,11 @@ public String toString() {
     }
 
     private void insertRangeTombstones(CassandraClient client, Map<Cell, Long> maxTimestampExclusiveByCell,
-            TableReference tableRef, boolean deleteSentinel) throws TException {
+            TableReference tableRef, boolean deleteSentinel, long rangeTombstoneCassandraTs) throws TException {
         MutationMap mutationMap = new MutationMap();
 
         maxTimestampExclusiveByCell.forEach((cell, maxTimestampExclusive) -> {
-            Mutation mutation = getMutation(cell, maxTimestampExclusive, deleteSentinel);
+            Mutation mutation = getMutation(cell, maxTimestampExclusive, deleteSentinel, rangeTombstoneCassandraTs);
 
             mutationMap.addMutationForCell(cell, tableRef, mutation);
         });
@@ -1810,15 +1826,16 @@ private void insertRangeTombstones(CassandraClient client, Map<Cell, Long> maxTi
                 deleteConsistency);
     }
 
-    private Mutation getMutation(Cell cell, long maxTimestampExclusive, boolean deleteSentinel) {
+    private Mutation getMutation(Cell cell, long maxTimestampExclusive,
+            boolean deleteSentinel, long rangeTombstoneCassandraTimestamp) {
         if (deleteSentinel) {
             return Mutations.rangeTombstoneIncludingSentinelForColumn(cell.getColumnName(), maxTimestampExclusive,
-                    mutationTimestampProvider.getRangeTombstoneTimestamp(maxTimestampExclusive));
+                    rangeTombstoneCassandraTimestamp);
         }
         return Mutations.rangeTombstoneForColumn(
                 cell.getColumnName(),
                 maxTimestampExclusive,
-                mutationTimestampProvider.getRangeTombstoneTimestamp(maxTimestampExclusive));
+                rangeTombstoneCassandraTimestamp);
     }
 
     /**

docs/source/release_notes/release-notes.rst

@@ -50,6 +50,11 @@ develop
     *    - Type
          - Change
 
+    *    - |fixed|
+         - With targeted sweep, We now only call timelock once per set of range tombstones we leave,
+           rather than once per cell.
+           (`Pull Request <https://github.com/palantir/atlasdb/pull/3305>`__)
+
     *    - |fixed|
          - We now consider only one row at a time when getting rows from the KVS with sweepable cells.
            (`Pull Request <https://github.com/palantir/atlasdb/pull/3302>`__)