wgtmac commented on code in PR #42133: URL: https://github.com/apache/arrow/pull/42133#discussion_r1638318695
########## cpp/src/arrow/array/statistics.h: ########## @@ -0,0 +1,84 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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. + +#pragma once + +#include <optional> +#include <variant> + +#include "arrow/util/visibility.h" + +namespace arrow { + +/// \brief Statistics for an Array +/// +/// Apache Arrow format doesn't have statistics but data source such +/// as Apache Parquet may have statistics. Statistics associate with +/// data source can be read unified API via this class. +struct ARROW_EXPORT ArrayStatistics { + public: + using ElementBufferType = std::variant<bool, int8_t, uint8_t, int16_t, uint16_t, Review Comment: Apart from var-len type, how do we support timestamp, internal and other primitive types? ########## cpp/src/arrow/array/statistics.h: ########## @@ -0,0 +1,84 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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. + +#pragma once + +#include <optional> +#include <variant> + +#include "arrow/util/visibility.h" + +namespace arrow { + +/// \brief Statistics for an Array +/// +/// Apache Arrow format doesn't have statistics but data source such +/// as Apache Parquet may have statistics. Statistics associate with +/// data source can be read unified API via this class. +struct ARROW_EXPORT ArrayStatistics { + public: + using ElementBufferType = std::variant<bool, int8_t, uint8_t, int16_t, uint16_t, Review Comment: BTW, should we add an optional buffer to store values for string/binary types? Thus we can use std::string_view to represent them. If the min/max values are exact values, we can point them to the values in the arrow array and do not store any value in the optional buffer. ########## cpp/src/arrow/array/statistics.h: ########## @@ -0,0 +1,84 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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. + +#pragma once + +#include <optional> +#include <variant> + +#include "arrow/util/visibility.h" + +namespace arrow { + +/// \brief Statistics for an Array +/// +/// Apache Arrow format doesn't have statistics but data source such +/// as Apache Parquet may have statistics. Statistics associate with +/// data source can be read unified API via this class. +struct ARROW_EXPORT ArrayStatistics { + public: + using ElementBufferType = std::variant<bool, int8_t, uint8_t, int16_t, uint16_t, + int32_t, uint32_t, int64_t, uint64_t>; + + ArrayStatistics() = default; + ~ArrayStatistics() = default; + + /// \brief The number of null values, may not be set + std::optional<int64_t> null_count = std::nullopt; + + /// \brief The number of distinct values, may not be set + std::optional<int64_t> distinct_count = std::nullopt; + + /// \brief The current minimum value buffer, may not be set + std::optional<ElementBufferType> min_buffer = std::nullopt; Review Comment: Are they exact min/max values, or they can be lower/upper bounds? Should we add a flag to indicate this case? FYI, parquet has a flag to indicate whether the value is exact or not. ########## cpp/src/arrow/array/statistics.h: ########## @@ -0,0 +1,84 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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. + +#pragma once + +#include <optional> +#include <variant> + +#include "arrow/util/visibility.h" + +namespace arrow { + +/// \brief Statistics for an Array +/// +/// Apache Arrow format doesn't have statistics but data source such +/// as Apache Parquet may have statistics. Statistics associate with +/// data source can be read unified API via this class. +struct ARROW_EXPORT ArrayStatistics { + public: + using ElementBufferType = std::variant<bool, int8_t, uint8_t, int16_t, uint16_t, + int32_t, uint32_t, int64_t, uint64_t>; + + ArrayStatistics() = default; + ~ArrayStatistics() = default; + + /// \brief The number of null values, may not be set + std::optional<int64_t> null_count = std::nullopt; + + /// \brief The number of distinct values, may not be set + std::optional<int64_t> distinct_count = std::nullopt; Review Comment: Is this really useful? AFAIK, Parquet does not populate this. ########## cpp/src/parquet/arrow/reader_internal.cc: ########## @@ -330,15 +331,30 @@ Status TransferInt(RecordReader* reader, MemoryPool* pool, auto values = reinterpret_cast<const ParquetCType*>(reader->values()); auto out_ptr = reinterpret_cast<ArrowCType*>(data->mutable_data()); std::copy(values, values + length, out_ptr); + int64_t null_count = 0; + std::vector<std::shared_ptr<Buffer>> buffers = {nullptr, std::move(data)}; if (field->nullable()) { - *out = std::make_shared<ArrayType<ArrowType>>(field->type(), length, std::move(data), - reader->ReleaseIsValid(), - reader->null_count()); - } else { - *out = - std::make_shared<ArrayType<ArrowType>>(field->type(), length, std::move(data), - /*null_bitmap=*/nullptr, /*null_count=*/0); + null_count = reader->null_count(); + buffers[0] = reader->ReleaseIsValid(); + } + auto array_data = + ::arrow::ArrayData::Make(field->type(), length, std::move(buffers), null_count); + array_data->statistics.null_count = null_count; + auto statistics = metadata->statistics().get(); + if (statistics) { + if (statistics->HasDistinctCount()) { + array_data->statistics.distinct_count = statistics->distinct_count(); + } + if (statistics->HasMinMax()) { + auto typed_statistics = + static_cast<::parquet::TypedStatistics<ParquetType>*>(statistics); + array_data->statistics.min_buffer = + static_cast<ArrowCType>(typed_statistics->min()); + array_data->statistics.max_buffer = + static_cast<ArrowCType>(typed_statistics->max()); + } } + *out = std::make_shared<ArrayType<ArrowType>>(std::move(array_data)); Review Comment: IIRC, the current parquet reader will return a chunked array containing one or multiple arrays (may or may not from different row groups). Here the stats do not contain the exact min/max values because they are from the row group level. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
