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feat(vector): Add support for flat map encoding in vector function map_filter #13829

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feat(vector): Add support for flat map encoding in vector function map_filter #13829

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208 changes: 194 additions & 14 deletions velox/functions/prestosql/FilterFunctions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
#include "velox/expression/VectorFunction.h"
#include "velox/functions/lib/LambdaFunctionUtil.h"
#include "velox/functions/lib/RowsTranslationUtil.h"
#include "velox/vector/FlatMapVector.h"
#include "velox/vector/FunctionVector.h"

namespace facebook::velox::functions {
Expand All @@ -34,7 +35,7 @@ class FilterFunctionBase : public exec::VectorFunction {
static vector_size_t doApply(
const SelectivityVector& rows,
const std::shared_ptr<T>& input,
const VectorPtr& lambdas,
const VectorPtr& lambda,
const std::vector<VectorPtr>& lambdaArgs,
exec::EvalCtx& context,
BufferPtr& resultOffsets,
Expand All @@ -60,7 +61,7 @@ class FilterFunctionBase : public exec::VectorFunction {
getElementToTopLevelRows(numElements, rows, input.get(), pool);

exec::LocalDecodedVector bitsDecoder(context);
auto iter = lambdas->asUnchecked<FunctionVector>()->iterator(&rows);
auto iter = lambda->asUnchecked<FunctionVector>()->iterator(&rows);
while (auto entry = iter.next()) {
auto elementRows =
toElementRows<T>(numElements, *entry.rows, input.get());
Expand Down Expand Up @@ -173,27 +174,177 @@ class ArrayFilterFunction : public FilterFunctionBase {
// - https://prestodb.io/docs/current/functions/lambda.html
// - https://prestodb.io/blog/2020/03/02/presto-lambda
class MapFilterFunction : public FilterFunctionBase {
public:
void apply(
private:
// Builds a SelectivityVector based upon FlatMapVector's inMap buffer. This
// buffer indicates whether or not a particular key is present in that map's
// row. When applying lambda functions we should avoid executing on key-value
// pairs that are not present in that particular row. SelectivityVector
// rowsToFilterOn is used to filter out those rows.
void buildInMapSelectivityVector(
SelectivityVector& rowsToFilterOn,
BufferPtr flattenedInMap,
BufferPtr inMap,
vector_size_t inMapSize,
const SelectivityVector& rows,
const vector_size_t* decodedIndices) const {
// Flatten inMap buffer.
auto* mutableFlattedInMap = flattenedInMap->asMutable<uint64_t>();
bits::fillBits(mutableFlattedInMap, 0, inMapSize, false);
auto* mutableInMap = inMap->asMutable<uint64_t>();
rows.applyToSelected([&](vector_size_t row) {
if (bits::isBitSet(mutableInMap, decodedIndices[row])) {
bits::setBit(mutableFlattedInMap, decodedIndices[row]);
}
});

// Extract flattened inMap buffer values for next lambda call.
rowsToFilterOn.clearAll();
auto bits = rowsToFilterOn.asMutableRange().bits();
bits::orBits(bits, mutableFlattedInMap, 0, rowsToFilterOn.size());
rowsToFilterOn.updateBounds();
}

// Apply filter function to vector of encoding FlatMapVector. Because the
// entirety of the map values are stored in in a list of vectors (one vector
// per key), we will need to apply the filter function on each vector and
// associated inMap buffer. Additionally, we will have to reduce the number of
// distinct keys stored in the FlatMapVector if they key list changes.
void applyFlatMapVector(
DecodedVector& decodedMap,
const SelectivityVector& rows,
std::vector<VectorPtr>& args,
const TypePtr& outputType,
exec::EvalCtx& context,
VectorPtr& result) const override {
VELOX_CHECK_EQ(args.size(), 2);
exec::LocalDecodedVector mapDecoder(context, *args[0], rows);
auto& decodedMap = *mapDecoder.get();
VectorPtr& result) const {
// Current map and fields
const FlatMapVector& flatMap =
*(decodedMap.base())->template as<FlatMapVector>();
auto distinctKeys = flatMap.distinctKeys();
auto mapValues = flatMap.mapValues();
auto numRows = rows.size();
BufferPtr decodedIndices =
AlignedBuffer::allocate<vector_size_t>(numRows, flatMap.pool());
auto mutableIndices = decodedIndices->asMutable<vector_size_t>();
for (int i = 0; i < decodedMap.size(); i++) {
mutableIndices[i] = decodedMap.indices()[i];
}

// Result map fields
auto filteredKeysIndices = AlignedBuffer::allocate<vector_size_t>(
distinctKeys->size(), context.pool());
std::vector<VectorPtr> filteredMapValues;
std::vector<BufferPtr> filteredInMaps;
uint64_t* filteredInMap;
auto numDistinct = 0;
auto rawIndices = filteredKeysIndices->asMutable<vector_size_t>();

// Lambda function
auto iter = args[1]->asUnchecked<FunctionVector>()->iterator(&rows);
exec::LocalDecodedVector bitsDecoder(context);
SelectivityVector rowsToFilterOn(flatMap.size());
// Selectivity vector to help ignore filtering for key-value pairs
// identified by inMap buffer. Let's allocate here to avoid during each
// iteration.
auto flattenedInMap =
AlignedBuffer::allocate<bool>(flatMap.size(), context.pool(), 0);

// Apply lambda function to each map value vector and its associated key
// from our flat map vector. If the key is not filtered out, we will copy it
// to our result vector.
while (auto entry = iter.next()) {
for (int channel = 0; channel < mapValues.size(); ++channel) {
// Only apply lambda function to values that are in the map.
buildInMapSelectivityVector(
rowsToFilterOn,
flattenedInMap,
flatMap.inMaps()[channel],
flatMap.size(),
*entry.rows,
decodedMap.indices());

// Call lambda function and decode its output bit vector. We will
// use it to determine what will persist to the final result vector.
VectorPtr lambdaResultBits;
entry.callable->apply(
rowsToFilterOn,
nullptr,
nullptr,
&context,
{
BaseVector::wrapInConstant(
flatMap.size(), channel, distinctKeys),
mapValues[channel],
},
decodedIndices,
&lambdaResultBits);
bitsDecoder.get()->decode(*lambdaResultBits);

bool isFilteredIn = false;
entry.rows->applyToSelected([&](vector_size_t row) {
row = decodedMap.indices()[row];
if (rowsToFilterOn.isValid(row) &&
!bitsDecoder.get()->isNullAt(row) &&
bitsDecoder.get()->valueAt<bool>(row)) {
// First time seeing this key; let's copy over its associated values
// vector and define a new filtered inMap buffer. Let's also note
// the index of this key for key filtering.
if (!isFilteredIn) {
filteredMapValues.push_back(
BaseVector::copy(*mapValues[channel]));
filteredInMaps.push_back(
AlignedBuffer::allocate<bool>(numRows, context.pool(), 0));
filteredInMap = filteredInMaps.back()->asMutable<uint64_t>();
rawIndices[numDistinct++] = channel;
isFilteredIn = true;
}
bits::setBit(filteredInMap, row);
}
});
}
}

// Resize filtered distinct keys indices in order to wrap in dictionary and
// create our result filtered flat map vector
filteredKeysIndices->setSize(numDistinct * sizeof(vector_size_t));
auto localResult = std::make_shared<FlatMapVector>(
context.pool(),
outputType,
nullptr,
flatMap.size(),
BaseVector::wrapInDictionary(
BufferPtr(nullptr), filteredKeysIndices, numDistinct, distinctKeys),
std::move(filteredMapValues),
std::move(filteredInMaps));

auto flatMap = flattenMap(rows, args[0], decodedMap);
// Handle wrapped encoding if necessary
if (decodedMap.isIdentityMapping()) {
context.moveOrCopyResult(localResult, rows, result);
} else {
context.moveOrCopyResult(
BaseVector::wrapInDictionary(
nullptr, decodedIndices, decodedMap.size(), localResult),
rows,
result);
}
}

VectorPtr keys = flatMap->mapKeys();
VectorPtr values = flatMap->mapValues();
// Applies filter function on traditional map vector.
void applyMapVector(
DecodedVector& decodedMap,
const SelectivityVector& rows,
std::vector<VectorPtr>& args,
const TypePtr& outputType,
exec::EvalCtx& context,
VectorPtr& result) const {
auto mapVector = flattenMap(rows, args[0], decodedMap);
VectorPtr keys = mapVector->mapKeys();
VectorPtr values = mapVector->mapValues();
BufferPtr resultSizes;
BufferPtr resultOffsets;
BufferPtr selectedIndices;
auto numSelected = doApply(
rows,
flatMap,
mapVector,
args[1],
{keys, values},
context,
Expand All @@ -220,9 +371,9 @@ class MapFilterFunction : public FilterFunctionBase {
true /*flattenIfRedundant*/)
: nullptr;
// Set nulls for rows not present in 'rows'.
BufferPtr newNulls = addNullsForUnselectedRows(flatMap, rows);
BufferPtr newNulls = addNullsForUnselectedRows(mapVector, rows);
auto localResult = std::make_shared<MapVector>(
flatMap->pool(),
mapVector->pool(),
outputType,
std::move(newNulls),
rows.end(),
Expand All @@ -233,6 +384,35 @@ class MapFilterFunction : public FilterFunctionBase {
context.moveOrCopyResult(localResult, rows, result);
}

public:
void apply(
const SelectivityVector& rows,
std::vector<VectorPtr>& args,
const TypePtr& outputType,
exec::EvalCtx& context,
VectorPtr& result) const override {
VELOX_CHECK_EQ(args.size(), 2);
exec::LocalDecodedVector mapDecoder(context, *args[0], rows);
auto& decodedMap = *mapDecoder.get();

// Flattening input maps will peel if possible, but may simply cast if the
// vector is an identify mapping.
switch (decodedMap.base()->encoding()) {
case VectorEncoding::Simple::FLAT_MAP: {
applyFlatMapVector(decodedMap, rows, args, outputType, context, result);
break;
}
case VectorEncoding::Simple::MAP: {
applyMapVector(decodedMap, rows, args, outputType, context, result);
break;
}
default:
VELOX_UNSUPPORTED(
"map_filter not supported for encoding: {}",
decodedMap.base()->encoding());
}
}

static std::vector<std::shared_ptr<exec::FunctionSignature>> signatures() {
// map(K,V), function(K,V,boolean) -> map(K,V)
return {exec::FunctionSignatureBuilder()
Expand Down
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