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Calculate Iceberg NDV with a Theta sketch
Iceberg specification defines the Apache DataSketches's Theta as the common data sketch for keeping track of distinct values in a table. This change replaces the use of HLL within Iceberg's ANALYZE with Theta sketch. The follow-up work is to store the serialized compact form of the sketch inside the Iceberg Puffin statistics file, but this requires Iceberg API changes, which are still in progress. A side effect of this change is that complex types (array, map, row) can no longer be analyzed: Trino can calculate a HyperLogLog for these types, while Iceberg does not specify binary representation for these types, which is required to feed data into a Theta sketch. However, NDV for complex types is not as useful as it is for scalar types, so this shouldn't matter in practice.
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32 changes: 32 additions & 0 deletions
32
plugin/trino-iceberg/src/main/java/io/trino/plugin/iceberg/aggregation/DataSketchState.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,32 @@ | ||
| /* | ||
| * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package io.trino.plugin.iceberg.aggregation; | ||
|
|
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| import io.trino.spi.function.AccumulatorState; | ||
| import io.trino.spi.function.AccumulatorStateMetadata; | ||
| import org.apache.datasketches.theta.CompactSketch; | ||
| import org.apache.datasketches.theta.UpdateSketch; | ||
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| @AccumulatorStateMetadata(stateSerializerClass = DataSketchStateSerializer.class) | ||
| public interface DataSketchState | ||
| extends AccumulatorState | ||
| { | ||
| UpdateSketch getUpdateSketch(); | ||
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| void setUpdateSketch(UpdateSketch value); | ||
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| CompactSketch getCompactSketch(); | ||
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| void setCompactSketch(CompactSketch value); | ||
| } |
73 changes: 73 additions & 0 deletions
73
...-iceberg/src/main/java/io/trino/plugin/iceberg/aggregation/DataSketchStateSerializer.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| /* | ||
| * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package io.trino.plugin.iceberg.aggregation; | ||
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|
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| import io.airlift.slice.Slice; | ||
| import io.airlift.slice.Slices; | ||
| import io.trino.spi.block.Block; | ||
| import io.trino.spi.block.BlockBuilder; | ||
| import io.trino.spi.function.AccumulatorStateSerializer; | ||
| import io.trino.spi.type.Type; | ||
| import org.apache.datasketches.memory.WritableMemory; | ||
| import org.apache.datasketches.theta.CompactSketch; | ||
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| import java.util.Optional; | ||
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| import static com.google.common.base.Preconditions.checkArgument; | ||
| import static io.trino.spi.type.VarbinaryType.VARBINARY; | ||
|
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| public class DataSketchStateSerializer | ||
| implements AccumulatorStateSerializer<DataSketchState> | ||
| { | ||
| @Override | ||
| public Type getSerializedType() | ||
| { | ||
| return VARBINARY; | ||
| } | ||
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| @Override | ||
| public void serialize(DataSketchState state, BlockBuilder out) | ||
| { | ||
| serializeToVarbinary(state, out); | ||
| } | ||
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| public static void serializeToVarbinary(DataSketchState state, BlockBuilder out) | ||
| { | ||
| if (state.getUpdateSketch() == null && state.getCompactSketch() == null) { | ||
| out.appendNull(); | ||
| } | ||
| else { | ||
| checkArgument(state.getUpdateSketch() == null || state.getCompactSketch() == null, "A state must not have both transient accumulator and combined form set"); | ||
| CompactSketch compactSketch = Optional.ofNullable(state.getCompactSketch()) | ||
| .orElseGet(() -> state.getUpdateSketch().compact()); | ||
| Slice slice = Slices.wrappedBuffer(compactSketch.toByteArray()); | ||
| VARBINARY.writeSlice(out, slice); | ||
| } | ||
| } | ||
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| @Override | ||
| public void deserialize(Block block, int index, DataSketchState state) | ||
| { | ||
| if (!block.isNull(index)) { | ||
| state.setCompactSketch(deserialize(block, index)); | ||
| } | ||
| } | ||
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| public static CompactSketch deserialize(Block block, int index) | ||
| { | ||
| checkArgument(!block.isNull(index), "Value is null"); | ||
| Slice slice = VARBINARY.getSlice(block, index); | ||
| return CompactSketch.heapify(WritableMemory.writableWrap(slice.getBytes())); | ||
| } | ||
| } |
124 changes: 124 additions & 0 deletions
124
...iceberg/src/main/java/io/trino/plugin/iceberg/aggregation/IcebergThetaSketchForStats.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| /* | ||
| * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package io.trino.plugin.iceberg.aggregation; | ||
|
|
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| import io.trino.spi.block.Block; | ||
| import io.trino.spi.block.BlockBuilder; | ||
| import io.trino.spi.function.AggregationFunction; | ||
| import io.trino.spi.function.AggregationState; | ||
| import io.trino.spi.function.BlockIndex; | ||
| import io.trino.spi.function.BlockPosition; | ||
| import io.trino.spi.function.CombineFunction; | ||
| import io.trino.spi.function.InputFunction; | ||
| import io.trino.spi.function.OutputFunction; | ||
| import io.trino.spi.function.SqlType; | ||
| import io.trino.spi.function.TypeParameter; | ||
| import io.trino.spi.type.StandardTypes; | ||
| import io.trino.spi.type.Type; | ||
| import org.apache.datasketches.Family; | ||
| import org.apache.datasketches.theta.SetOperation; | ||
| import org.apache.datasketches.theta.Sketch; | ||
| import org.apache.datasketches.theta.Union; | ||
| import org.apache.datasketches.theta.UpdateSketch; | ||
| import org.apache.iceberg.types.Conversions; | ||
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| import javax.annotation.Nullable; | ||
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| import java.nio.ByteBuffer; | ||
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| import static com.google.common.base.Verify.verify; | ||
| import static io.trino.plugin.iceberg.IcebergTypes.convertTrinoValueToIceberg; | ||
| import static io.trino.plugin.iceberg.TypeConverter.toIcebergType; | ||
| import static io.trino.spi.type.TypeUtils.readNativeValue; | ||
| import static java.util.Objects.requireNonNull; | ||
|
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| @AggregationFunction(value = IcebergThetaSketchForStats.NAME, hidden = true) | ||
| public final class IcebergThetaSketchForStats | ||
| { | ||
| private IcebergThetaSketchForStats() {} | ||
|
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| public static final String NAME = "$iceberg_theta_stat"; | ||
|
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| @InputFunction | ||
| @TypeParameter("T") | ||
| public static void input(@TypeParameter("T") Type type, @AggregationState DataSketchState state, @BlockPosition @SqlType("T") Block block, @BlockIndex int index) | ||
| { | ||
| verify(!block.isNull(index), "Input function is not expected to be called on a NULL input"); | ||
|
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| Object trinoValue = readNativeValue(type, block, index); | ||
| org.apache.iceberg.types.Type icebergType = toIcebergType(type); | ||
| Object icebergValue = convertTrinoValueToIceberg(type, trinoValue); | ||
| ByteBuffer byteBuffer = Conversions.toByteBuffer(icebergType, icebergValue); | ||
| requireNonNull(byteBuffer, "byteBuffer is null"); // trino value isn't null | ||
| byte[] bytes = getBytes(byteBuffer); | ||
| getOrCreateUpdateSketch(state).update(bytes); | ||
| } | ||
|
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| @CombineFunction | ||
| public static void combine(@AggregationState DataSketchState state, @AggregationState DataSketchState otherState) | ||
| { | ||
| Union union = SetOperation.builder().buildUnion(); | ||
| addIfPresent(union, state.getUpdateSketch()); | ||
| addIfPresent(union, state.getCompactSketch()); | ||
| addIfPresent(union, otherState.getUpdateSketch()); | ||
| addIfPresent(union, otherState.getCompactSketch()); | ||
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| state.setUpdateSketch(null); | ||
| state.setCompactSketch(union.getResult()); | ||
| } | ||
|
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| @OutputFunction(StandardTypes.VARBINARY) | ||
| public static void output(@AggregationState DataSketchState state, BlockBuilder out) | ||
| { | ||
| if (state.getUpdateSketch() == null && state.getCompactSketch() == null) { | ||
| getOrCreateUpdateSketch(state); | ||
| } | ||
| DataSketchStateSerializer.serializeToVarbinary(state, out); | ||
| } | ||
|
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| private static UpdateSketch getOrCreateUpdateSketch(@AggregationState DataSketchState state) | ||
| { | ||
| UpdateSketch sketch = state.getUpdateSketch(); | ||
| if (sketch == null) { | ||
| // Must match Iceberg table statistics specification | ||
| // https://iceberg.apache.org/puffin-spec/#apache-datasketches-theta-v1-blob-type | ||
| sketch = UpdateSketch.builder() | ||
| .setFamily(Family.ALPHA) | ||
| .build(); | ||
| state.setUpdateSketch(sketch); | ||
| } | ||
| return sketch; | ||
| } | ||
|
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| private static void addIfPresent(Union union, @Nullable Sketch input) | ||
| { | ||
| if (input != null) { | ||
| union.union(input); | ||
| } | ||
| } | ||
|
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| private static byte[] getBytes(ByteBuffer byteBuffer) | ||
| { | ||
| int length = byteBuffer.remaining(); | ||
| if (byteBuffer.hasArray() && byteBuffer.arrayOffset() == 0) { | ||
| byte[] bytes = byteBuffer.array(); | ||
| if (bytes.length == length) { | ||
| return bytes; | ||
| } | ||
| } | ||
| byte[] bytes = new byte[length]; | ||
| byteBuffer.get(bytes); | ||
| return bytes; | ||
| } | ||
| } |
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