rdettai commented on a change in pull request #1141: URL: https://github.com/apache/arrow-datafusion/pull/1141#discussion_r735326567
########## File path: datafusion/src/datasource/listing/helpers.rs ########## @@ -0,0 +1,682 @@ +// 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. + +//! Helper functions for the table implementation + +use std::sync::Arc; + +use arrow::{ + array::{ + Array, ArrayBuilder, ArrayRef, Date64Array, Date64Builder, StringArray, + StringBuilder, UInt64Array, UInt64Builder, + }, + datatypes::{DataType, Field, Schema}, + record_batch::RecordBatch, +}; +use chrono::{TimeZone, Utc}; +use futures::{ + stream::{self}, + StreamExt, TryStreamExt, +}; +use log::debug; + +use crate::{ + error::Result, + execution::context::ExecutionContext, + logical_plan::{self, Expr}, + physical_plan::functions::Volatility, + scalar::ScalarValue, +}; + +use crate::datasource::{ + object_store::{FileMeta, ObjectStore, SizedFile}, + MemTable, PartitionedFile, PartitionedFileStream, +}; + +const FILE_SIZE_COLUMN_NAME: &str = "_df_part_file_size_"; +const FILE_PATH_COLUMN_NAME: &str = "_df_part_file_path_"; +const FILE_MODIFIED_COLUMN_NAME: &str = "_df_part_file_modified_"; + +/// Partition the list of files into `n` groups +pub fn split_files( + partitioned_files: Vec<PartitionedFile>, + n: usize, +) -> Vec<Vec<PartitionedFile>> { + if partitioned_files.is_empty() { + return vec![]; + } + let mut chunk_size = partitioned_files.len() / n; + if partitioned_files.len() % n > 0 { + chunk_size += 1; + } + partitioned_files + .chunks(chunk_size) + .map(|c| c.to_vec()) + .collect() +} + +/// Discover the partitions on the given path and prune out files +/// relative to irrelevant partitions using `filters` expressions +/// TODO for tables with many files (10k+), it will usually more efficient +/// to first list the folders relative to the first partition dimension, +/// prune those, then list only the contain of the remaining folders. +pub async fn pruned_partition_list( + store: &dyn ObjectStore, + table_path: &str, + filters: &[Expr], + file_extension: &str, + table_partition_dims: &[String], +) -> Result<PartitionedFileStream> { + if table_partition_dims.is_empty() { + Ok(Box::pin( + store + .list_file_with_suffix(table_path, file_extension) + .await? + .map(|f| { + Ok(PartitionedFile { + file_meta: f?, + partition_values: vec![], + }) + }), + )) + } else { + let applicable_filters = filters + .iter() + .filter(|f| expr_applicable_for_cols(table_partition_dims, f)); + + let table_partition_dims = table_partition_dims.to_vec(); + let stream_path = table_path.to_owned(); + // TODO avoid collecting but have a streaming memory table instead + let batches: Vec<RecordBatch> = store + .list_file_with_suffix(table_path, file_extension) + .await? + .chunks(64) + .map(|v| v.into_iter().collect::<Result<Vec<_>>>()) + .map(move |metas| { + paths_to_batch(&table_partition_dims, &stream_path, &metas?) + }) + .try_collect() + .await?; + + let mem_table = MemTable::try_new(batches[0].schema(), vec![batches])?; + + // Filter the partitions using a local datafusion context + // TODO having the external context would allow us to resolve `Volatility::Stable` + // scalar functions (`ScalarFunction` & `ScalarUDF`) and `ScalarVariable`s + let mut ctx = ExecutionContext::new(); + let mut df = ctx.read_table(Arc::new(mem_table))?; + for filter in applicable_filters { + df = df.filter(filter.clone())?; + } + let filtered_batches = df.collect().await?; + + Ok(Box::pin(stream::iter( + batches_to_paths(&filtered_batches).into_iter().map(Ok), + ))) + } +} + +/// convert the paths of the files to a record batch with the following columns: +/// - one column for the file size named `_df_part_file_size_` +/// - one column for with the original path named `_df_part_file_path_` +/// - one column for with the last modified date named `_df_part_file_modified_` +/// - ... one column by partition ... +/// Note: For the last modified date, this looses precisions higher than millisecond. +fn paths_to_batch( + table_partition_dims: &[String], + table_path: &str, + metas: &[FileMeta], +) -> Result<RecordBatch> { + let mut key_builder = StringBuilder::new(metas.len()); + let mut length_builder = UInt64Builder::new(metas.len()); + let mut modified_builder = Date64Builder::new(metas.len()); + let mut partition_builders = table_partition_dims + .iter() + .map(|_| StringBuilder::new(metas.len())) + .collect::<Vec<_>>(); + for file_meta in metas { + if let Some(partition_values) = + parse_partitions_for_path(table_path, file_meta.path(), table_partition_dims) + { + key_builder.append_value(file_meta.path())?; + length_builder.append_value(file_meta.size())?; + match file_meta.last_modified { + Some(lm) => modified_builder.append_value(lm.timestamp_millis())?, + None => modified_builder.append_null()?, + } + for (i, part_val) in partition_values.iter().enumerate() { + partition_builders[i].append_value(part_val)?; + } + } else { + debug!("No partitioning for path {}", file_meta.path()); + } + } + + // finish all builders + let mut col_arrays: Vec<ArrayRef> = vec![ + ArrayBuilder::finish(&mut key_builder), + ArrayBuilder::finish(&mut length_builder), + ArrayBuilder::finish(&mut modified_builder), + ]; + for mut partition_builder in partition_builders { + col_arrays.push(ArrayBuilder::finish(&mut partition_builder)); + } + + // put the schema together + let mut fields = vec![ + Field::new(FILE_SIZE_COLUMN_NAME, DataType::Utf8, false), + Field::new(FILE_PATH_COLUMN_NAME, DataType::UInt64, false), Review comment: yes thanks -- This is an automated message from the Apache Git Service. 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