tustvold commented on code in PR #8294: URL: https://github.com/apache/arrow-datafusion/pull/8294#discussion_r1406752147
########## datafusion/core/src/datasource/physical_plan/parquet/statistics.rs: ########## @@ -0,0 +1,807 @@ +// 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. + +//! [`RowGroupStatisticsConverter`] tp converts parquet RowGroup statistics to arrow [`ArrayRef`]. + +use arrow::{array::ArrayRef, datatypes::DataType}; +use arrow_array::new_empty_array; +use arrow_schema::Field; +use datafusion_common::{Result, ScalarValue}; +use parquet::file::{ + metadata::RowGroupMetaData, statistics::Statistics as ParquetStatistics, +}; + +// Convert the bytes array to i128. +// The endian of the input bytes array must be big-endian. +pub(crate) fn from_bytes_to_i128(b: &[u8]) -> i128 { + // The bytes array are from parquet file and must be the big-endian. + // The endian is defined by parquet format, and the reference document + // https://github.com/apache/parquet-format/blob/54e53e5d7794d383529dd30746378f19a12afd58/src/main/thrift/parquet.thrift#L66 + i128::from_be_bytes(sign_extend_be(b)) +} + +// Copy from arrow-rs +// https://github.com/apache/arrow-rs/blob/733b7e7fd1e8c43a404c3ce40ecf741d493c21b4/parquet/src/arrow/buffer/bit_util.rs#L55 +// Convert the byte slice to fixed length byte array with the length of 16 +fn sign_extend_be(b: &[u8]) -> [u8; 16] { + assert!(b.len() <= 16, "Array too large, expected less than 16"); + let is_negative = (b[0] & 128u8) == 128u8; + let mut result = if is_negative { [255u8; 16] } else { [0u8; 16] }; + for (d, s) in result.iter_mut().skip(16 - b.len()).zip(b) { + *d = *s; + } + result +} + +/// Converts parquet RowGroup statistics (stored in +/// [`RowGroupMetaData`]) into an arrow [`ArrayRef`] +/// +/// For example, given a parquet file with 3 Row Groups, when asked for +/// statistics for column "A" it will return a single array with 3 elements, +/// +pub(crate) struct RowGroupStatisticsConverter<'a> { + field: &'a Field, +} + +/// Extract a single min/max statistics from a [`ParquetStatistics`] object +/// +/// * `$column_statistics` is the `ParquetStatistics` object +/// * `$func is the function` (`min`/`max`) to call to get the value +/// * `$bytes_func` is the function (`min_bytes`/`max_bytes`) to call to get the value as bytes +/// * `$target_arrow_type` is the [`DataType`] of the target statistics +macro_rules! get_statistic { + ($column_statistics:expr, $func:ident, $bytes_func:ident, $target_arrow_type:expr) => {{ + if !$column_statistics.has_min_max_set() { + return None; + } + match $column_statistics { + ParquetStatistics::Boolean(s) => Some(ScalarValue::Boolean(Some(*s.$func()))), + ParquetStatistics::Int32(s) => { + match $target_arrow_type { + // int32 to decimal with the precision and scale + Some(DataType::Decimal128(precision, scale)) => { + Some(ScalarValue::Decimal128( + Some(*s.$func() as i128), + precision, + scale, + )) + } + _ => Some(ScalarValue::Int32(Some(*s.$func()))), + } + } + ParquetStatistics::Int64(s) => { + match $target_arrow_type { + // int64 to decimal with the precision and scale + Some(DataType::Decimal128(precision, scale)) => { + Some(ScalarValue::Decimal128( + Some(*s.$func() as i128), + precision, + scale, + )) + } + _ => Some(ScalarValue::Int64(Some(*s.$func()))), + } + } + // 96 bit ints not supported + ParquetStatistics::Int96(_) => None, + ParquetStatistics::Float(s) => Some(ScalarValue::Float32(Some(*s.$func()))), + ParquetStatistics::Double(s) => Some(ScalarValue::Float64(Some(*s.$func()))), + ParquetStatistics::ByteArray(s) => { + match $target_arrow_type { + // decimal data type + Some(DataType::Decimal128(precision, scale)) => { + Some(ScalarValue::Decimal128( + Some(from_bytes_to_i128(s.$bytes_func())), + precision, + scale, + )) + } + _ => { + let s = std::str::from_utf8(s.$bytes_func()) + .map(|s| s.to_string()) + .ok(); + Some(ScalarValue::Utf8(s)) + } + } + } + // type not supported yet + ParquetStatistics::FixedLenByteArray(s) => { + match $target_arrow_type { + // just support the decimal data type + Some(DataType::Decimal128(precision, scale)) => { + Some(ScalarValue::Decimal128( + Some(from_bytes_to_i128(s.$bytes_func())), + precision, + scale, + )) + } + _ => None, + } + } + } + }}; +} + +#[derive(Debug, Clone, Copy)] +enum MinMax { + Min, + Max, +} + +impl<'a> RowGroupStatisticsConverter<'a> { Review Comment: > columns by their name (in the arrow Schema) The problem is this is not how parquet addresses the columns, and trying to pretend otherwise is going to result in a number of peculiar bugs -- This is an automated message from the Apache Git Service. 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