tustvold commented on code in PR #2045: URL: https://github.com/apache/arrow-rs/pull/2045#discussion_r918375540
########## parquet/src/column/writer/encoder.rs: ########## @@ -0,0 +1,247 @@ +// 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. + +use crate::basic::Encoding; +use crate::column::writer::{compare_greater, fallback_encoding, has_dictionary_support, is_nan, update_max, update_min}; +use crate::data_type::private::ParquetValueType; +use crate::data_type::DataType; +use crate::encodings::encoding::{get_encoder, DictEncoder, Encoder}; +use crate::errors::{ParquetError, Result}; +use crate::file::properties::WriterProperties; +use crate::schema::types::{ColumnDescPtr, ColumnDescriptor}; +use crate::util::memory::ByteBufferPtr; + +/// A collection of [`ParquetValueType`] encoded by a [`ColumnValueEncoder`] +pub trait ColumnValues { + /// The underlying value type + type T: ParquetValueType; + + /// The number of values in this collection + fn len(&self) -> usize; + + /// Returns the min and max values in this collection, skipping any NaN values + /// + /// Returns `None` if no values found + fn min_max(&self, descr: &ColumnDescriptor) -> Option<(&Self::T, &Self::T)>; +} + +/// The encoded data for a dictionary page +pub struct DictionaryPage { + pub buf: ByteBufferPtr, + pub num_values: usize, + pub is_sorted: bool, +} + +/// The encoded values for a data page, with optional statistics +pub struct DataPageValues<T> { + pub buf: ByteBufferPtr, + pub num_values: usize, + pub encoding: Encoding, + pub min_value: Option<T>, + pub max_value: Option<T>, +} + +/// A generic encoder of [`ColumnValues`] to data and dictionary pages used by +/// [super::GenericColumnWriter`] +pub trait ColumnValueEncoder { + /// The underlying value type of [`Self::Values`] + /// + /// Note: this avoids needing to fully qualify `<Self::Values as ColumnValues>::T` + type T: ParquetValueType; + + /// The values encoded by this encoder + type Values: ColumnValues<T = Self::T> + ?Sized; + + /// Create a new [`ColumnValueEncoder`] + fn try_new(descr: &ColumnDescPtr, props: &WriterProperties) -> Result<Self> + where + Self: Sized; + + /// Write the corresponding values to this [`ColumnValueEncoder`] + fn write(&mut self, values: &Self::Values, offset: usize, len: usize) -> Result<()>; + + /// Returns the number of buffered values + fn num_values(&self) -> usize; + + /// Returns true if this encoder has a dictionary page + fn has_dictionary(&self) -> bool; + + /// Returns an estimate of the dictionary page size in bytes, or `None` if no dictionary + fn estimated_dict_page_size(&self) -> Option<usize>; + + /// Returns an estimate of the data page size in bytes + fn estimated_data_page_size(&self) -> usize; + + /// Flush the dictionary page for this column chunk if any. Any subsequent calls to + /// [`Self::write`] will not be dictionary encoded + /// + /// Note: [`Self::flush_data_page`] must be called first, as this will error if there + /// are any pending page values + fn flush_dict_page(&mut self) -> Result<Option<DictionaryPage>>; + + /// Flush the next data page for this column chunk + fn flush_data_page(&mut self) -> Result<DataPageValues<Self::T>>; +} + +pub struct ColumnValueEncoderImpl<T: DataType> { + encoder: Box<dyn Encoder<T>>, + dict_encoder: Option<DictEncoder<T>>, + descr: ColumnDescPtr, + num_values: usize, + min_value: Option<T::T>, + max_value: Option<T::T>, +} + +impl<T: DataType> ColumnValueEncoder for ColumnValueEncoderImpl<T> { + type T = T::T; + + type Values = [T::T]; + + fn try_new(descr: &ColumnDescPtr, props: &WriterProperties) -> Result<Self> { + let dict_supported = props.dictionary_enabled(descr.path()) + && has_dictionary_support(T::get_physical_type(), &props); + let dict_encoder = dict_supported.then(|| DictEncoder::new(descr.clone())); + + // Set either main encoder or fallback encoder. + let encoder = get_encoder( + descr.clone(), + props + .encoding(descr.path()) + .unwrap_or_else(|| fallback_encoding(T::get_physical_type(), &props)), + )?; + + Ok(Self { + encoder, + dict_encoder, + descr: descr.clone(), + num_values: 0, + min_value: None, + max_value: None, + }) + } + + fn write(&mut self, values: &[T::T], offset: usize, len: usize) -> Result<()> { + self.num_values += len; + + let slice = values.get(offset..offset + len).ok_or_else(|| { + general_err!( + "Expected to write {} values, but have only {}", + len, + values.len() - offset + ) + })?; + + if let Some((min, max)) = slice.min_max(&self.descr) { + update_min(&self.descr, min, &mut self.min_value); + update_max(&self.descr, max, &mut self.max_value); + } + + match &mut self.dict_encoder { + Some(encoder) => encoder.put(slice), + _ => self.encoder.put(slice), + } + } + + fn num_values(&self) -> usize { + self.num_values + } + + fn has_dictionary(&self) -> bool { + self.dict_encoder.is_some() + } + + fn estimated_dict_page_size(&self) -> Option<usize> { + Some(self.dict_encoder.as_ref()?.dict_encoded_size()) + } + + fn estimated_data_page_size(&self) -> usize { + match &self.dict_encoder { + Some(encoder) => encoder.estimated_data_encoded_size(), + _ => self.encoder.estimated_data_encoded_size(), + } + } + + fn flush_dict_page(&mut self) -> Result<Option<DictionaryPage>> { + match self.dict_encoder.take() { + Some(encoder) => { + if self.num_values != 0 { + return Err(general_err!( + "Must flush data pages before flushing dictionary" + )); + } + + let buf = encoder.write_dict()?; + + Ok(Some(DictionaryPage { + buf, + num_values: encoder.num_entries(), + is_sorted: encoder.is_sorted(), + })) + } + _ => Ok(None), + } + } + + fn flush_data_page(&mut self) -> Result<DataPageValues<T::T>> { + let (buf, encoding) = match &mut self.dict_encoder { + Some(encoder) => (encoder.write_indices()?, Encoding::RLE_DICTIONARY), + _ => (self.encoder.flush_buffer()?, self.encoder.encoding()), + }; + + Ok(DataPageValues { + buf, + encoding, + num_values: std::mem::take(&mut self.num_values), Review Comment: Because it isn't an Option -- This is an automated message from the Apache Git Service. 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