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feat: avoid spurious tombstones in table output #6405

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merged 5 commits into from
Oct 12, 2020
Merged

feat: avoid spurious tombstones in table output #6405

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a10e5eb
chore: fix master build
big-andy-coates Oct 12, 2020
cc7f1da
feat: avoid supurious tombstones
big-andy-coates Oct 12, 2020
fcee2d4
test: updated test & historical plans
big-andy-coates Oct 12, 2020
8bc96c1
test: temp disable historical plans that fail
big-andy-coates Oct 12, 2020
64480bf
test: disable _correct_ tests ;)
big-andy-coates Oct 12, 2020
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63 changes: 0 additions & 63 deletions ksqldb-engine/src/test/java/io/confluent/ksql/function/KudafUndoAggregatorTest.java
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10 changes: 6 additions & 4 deletions ...db-execution/src/main/java/io/confluent/ksql/execution/function/udaf/KudafAggregator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -52,9 +52,11 @@ public KudafAggregator(

@Override
public GenericRow apply(final K k, final GenericRow rowValue, final GenericRow aggRowValue) {
final GenericRow result = GenericRow.fromList(aggRowValue.values());
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Kafka Streams does not expect the aggregator to mutate its parameters. The streams code is passing in the "old value", which ksqlDB was then mutating and returning as the "new value". This meant, when then function returned, the old and new values matched. This is obviously bad!

Code now takes a copy and mutates that. There is a perf hit, obviously, but it's unavoidable.

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Not sure I understand -- why did the old code work, in that case? Or did something change on the Streams side recently?

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The old code works because we were never enabling the sending of old values. We now do, to avoid the spurious tombstones.

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Sorry, still not understanding. What was being sent before, if not the old values? Was this method even being called, previously?

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The processing nodes in the streams topology can optionally include the old/previous value, as well as the new/current value, to child nodes. This is not on by default. An upstream change to how table filters is handled means this is now turned on.

The streams code for aggregation looks something like:

V process(K key, Change<V> change) {
   // Get old value from store:
   final V oldAgg = store.get(key);

   // Undo any previous value:
  final T intermediateAgg = value.oldValue != null && oldAgg != null
    ? remove.apply(key, value.oldValue, oldAgg)
    : oldAgg;

   // Then add the new value
   final T newAgg;
   if (value.newValue != null) {
       final T initializedAgg = intermediateAgg == null
         ?  initializer.apply();
          : intermediateAgg;

       newAgg = add.apply(key, value.newValue, initializedAgg);
   } else {
       newAgg = intermediateAgg;
   }

   // update the store with the new value. & forard
   store.put(key, newAgg);
   tupleForwarder.maybeForward(key, newAgg, sendOldValues ? oldAgg : null);
}

The two calls: remove.apply(key, value.oldValue, oldAgg) and add.apply(key, value.newValue, initializedAgg) are calling out to ksqlDB code. If these calls directly mutate the oldAgg or initializedAgg parameters passed, rather than creating copies, then the old and new values forwarded to child nodes will match. i.e. in tupleForwarder.maybeForward(key, newAgg, sendOldValues ? oldAgg : null), the parameters newAgg and oldAgg will have the same updated value, rather than oldAgg holding the previous value. This breaks downstream processes, which expect the old and new value.

Previously the nodes weren't configured to send old values, so where just sending null for the old value and downstream could handle this correctly.


// copy over group-by and aggregate parameter columns into the output row
for (int idx = 0; idx < nonAggColumnCount; idx++) {
aggRowValue.set(idx, rowValue.get(idx));
result.set(idx, rowValue.get(idx));
}

// compute the aggregation and write it into the output row. Its assumed that
Expand All @@ -63,12 +65,12 @@ public GenericRow apply(final K k, final GenericRow rowValue, final GenericRow a
for (int idx = nonAggColumnCount; idx < columnCount; idx++) {
final KsqlAggregateFunction<Object, Object, Object> func = aggregateFunctionForColumn(idx);
final Object currentValue = rowValue.get(func.getArgIndexInValue());
final Object currentAggregate = aggRowValue.get(idx);
final Object currentAggregate = result.get(idx);
final Object newAggregate = func.aggregate(currentValue, currentAggregate);
aggRowValue.set(idx, newAggregate);
result.set(idx, newAggregate);
}

return aggRowValue;
return result;
}

public KsqlTransformer<K, GenericRow> getResultMapper() {
Expand Down
10 changes: 6 additions & 4 deletions ...xecution/src/main/java/io/confluent/ksql/execution/function/udaf/KudafUndoAggregator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -51,17 +51,19 @@ public KudafUndoAggregator(
@SuppressWarnings({"unchecked", "rawtypes"})
@Override
public GenericRow apply(final Struct k, final GenericRow rowValue, final GenericRow aggRowValue) {
final GenericRow result = GenericRow.fromList(aggRowValue.values());
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As above.


for (int idx = 0; idx < nonAggColumnCount; idx++) {
aggRowValue.set(idx, rowValue.get(idx));
result.set(idx, rowValue.get(idx));
}

for (int idx = nonAggColumnCount; idx < columnCount; idx++) {
final TableAggregationFunction function = aggregateFunctions.get(idx - nonAggColumnCount);
final Object argument = rowValue.get(function.getArgIndexInValue());
final Object previous = aggRowValue.get(idx);
aggRowValue.set(idx, function.undo(argument, previous));
final Object previous = result.get(idx);
result.set(idx, function.undo(argument, previous));
}

return aggRowValue;
return result;
}
}
107 changes: 107 additions & 0 deletions ...xecution/src/test/java/io/confluent/ksql/execution/function/udaf/KudafAggregatorTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,107 @@
/*
* Copyright 2020 Confluent Inc.
*
* Licensed under the Confluent Community License (the "License"); you may not use
* this file except in compliance with the License. You may obtain a copy of the
* License at
*
* http://www.confluent.io/confluent-community-license
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/

package io.confluent.ksql.execution.function.udaf;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.not;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.when;

import com.google.common.collect.ImmutableList;
import io.confluent.ksql.GenericRow;
import io.confluent.ksql.execution.transform.KsqlProcessingContext;
import io.confluent.ksql.function.KsqlAggregateFunction;
import java.util.function.Function;
import org.apache.kafka.connect.data.Struct;
import org.apache.kafka.streams.kstream.Merger;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnitRunner;

@RunWith(MockitoJUnitRunner.class)
public class KudafAggregatorTest {

@Mock
private KsqlAggregateFunction<Long, String, String> func1;
@Mock
private Struct key;
@Mock
private Merger<Struct, String> func1Merger;
@Mock
private Function<String, String> func1ResultMapper;
@Mock
private KsqlProcessingContext ctx;
private KudafAggregator<String> aggregator;

@Before
public void setUp() {
aggregator = new KudafAggregator<>(2, ImmutableList.of(func1));

when(func1.getMerger()).thenReturn(func1Merger);
when(func1.getResultMapper()).thenReturn(func1ResultMapper);

when(func1.aggregate(any(), any())).thenReturn("func1-result");
when(func1Merger.apply(any(), any(), any())).thenReturn("func1-merged");
when(func1ResultMapper.apply(any())).thenReturn("func1-result");
}

@Test
public void shouldNotMutateParametersOnApply() {
// Given:
final GenericRow value = GenericRow.genericRow(1, 2L);
final GenericRow agg = GenericRow.genericRow(1, 2L, 3);

// When:
final GenericRow result = aggregator.apply("key", value, agg);

// Then:
assertThat(value, is(GenericRow.genericRow(1, 2L)));
assertThat(agg, is(GenericRow.genericRow(1, 2L, 3)));
assertThat("invalid test", result, is(not(GenericRow.genericRow(1, 2L, 3))));
}

@Test
public void shouldNotMutateParametersOnMerge() {
// Given:
final GenericRow aggOne = GenericRow.genericRow(1, 2L, 4);
final GenericRow aggTwo = GenericRow.genericRow(1, 2L, 3);

// When:
final GenericRow result = aggregator.getMerger().apply(key, aggOne, aggTwo);

// Then:
assertThat(aggOne, is(GenericRow.genericRow(1, 2L, 4)));
assertThat(aggTwo, is(GenericRow.genericRow(1, 2L, 3)));
assertThat("invalid test", result, is(not(GenericRow.genericRow(1, 2L, 4))));
assertThat("invalid test", result, is(not(GenericRow.genericRow(1, 2L, 3))));
}

@Test
public void shouldNotMutateParametersOnResultsMap() {
// Given:
final GenericRow agg = GenericRow.genericRow(1, 2L, 4);

// When:
final GenericRow result = aggregator.getResultMapper().transform("k", agg, ctx);

// Then:
assertThat(agg, is(GenericRow.genericRow(1, 2L, 4)));
assertThat("invalid test", result, is(not(GenericRow.genericRow(1, 2L, 4))));
}
}
79 changes: 79 additions & 0 deletions ...tion/src/test/java/io/confluent/ksql/execution/function/udaf/KudafUndoAggregatorTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,79 @@
/*
* Copyright 2020 Confluent Inc.
*
* Licensed under the Confluent Community License (the "License"); you may not use
* this file except in compliance with the License. You may obtain a copy of the
* License at
*
* http://www.confluent.io/confluent-community-license
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/

package io.confluent.ksql.execution.function.udaf;

import static io.confluent.ksql.GenericRow.genericRow;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.not;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.when;

import com.google.common.collect.ImmutableList;
import io.confluent.ksql.GenericRow;
import io.confluent.ksql.execution.function.TableAggregationFunction;
import org.apache.kafka.connect.data.Struct;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnitRunner;

@RunWith(MockitoJUnitRunner.class)
public class KudafUndoAggregatorTest {

@Mock
private TableAggregationFunction<Long, String, String> func1;
@Mock
private Struct key;
private KudafUndoAggregator aggregator;

@Before
public void setUp() {
aggregator = new KudafUndoAggregator(2, ImmutableList.of(func1));

when(func1.undo(any(), any())).thenReturn("func1-undone");
}

@Test
public void shouldNotMutateParametersOnApply() {
// Given:
final GenericRow value = GenericRow.genericRow(1, 2L);
final GenericRow agg = GenericRow.genericRow(1, 2L, 3);

// When:
final GenericRow result = aggregator.apply(key, value, agg);

// Then:
assertThat(value, is(GenericRow.genericRow(1, 2L)));
assertThat(agg, is(GenericRow.genericRow(1, 2L, 3)));
assertThat("invalid test", result, is(not(GenericRow.genericRow(1, 2L, 3))));
}

@Test
public void shouldApplyUndoableAggregateFunctions() {
// Given:
final GenericRow value = genericRow(1, 2L);
final GenericRow aggRow = genericRow(1, 2L, 3);

// When:
final GenericRow resultRow = aggregator.apply(key, value, aggRow);

// Then:
assertThat(resultRow, equalTo(genericRow(1, 2L, "func1-undone")));
}
}