alamb commented on code in PR #10701: URL: https://github.com/apache/datafusion/pull/10701#discussion_r1639702390
########## datafusion-examples/examples/advanced_parquet_index.rs: ########## @@ -0,0 +1,656 @@ +// 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 arrow::array::{ArrayRef, Int32Array, RecordBatch, StringArray}; +use arrow_schema::SchemaRef; +use async_trait::async_trait; +use bytes::Bytes; +use datafusion::datasource::listing::PartitionedFile; +use datafusion::datasource::physical_plan::parquet::{ + ParquetAccessPlan, ParquetExecBuilder, +}; +use datafusion::datasource::physical_plan::{ + parquet::ParquetFileReaderFactory, FileMeta, FileScanConfig, +}; +use datafusion::datasource::TableProvider; +use datafusion::execution::context::SessionState; +use datafusion::execution::object_store::ObjectStoreUrl; +use datafusion::parquet::arrow::arrow_reader::{ + ArrowReaderOptions, ParquetRecordBatchReaderBuilder, RowSelection, RowSelector, +}; +use datafusion::parquet::arrow::async_reader::{AsyncFileReader, ParquetObjectReader}; +use datafusion::parquet::arrow::ArrowWriter; +use datafusion::parquet::file::metadata::ParquetMetaData; +use datafusion::parquet::file::properties::{EnabledStatistics, WriterProperties}; +use datafusion::parquet::schema::types::ColumnPath; +use datafusion::physical_expr::PhysicalExpr; +use datafusion::physical_optimizer::pruning::PruningPredicate; +use datafusion::physical_plan::metrics::ExecutionPlanMetricsSet; +use datafusion::physical_plan::ExecutionPlan; +use datafusion::prelude::*; +use datafusion_common::{ + internal_datafusion_err, DFSchema, DataFusionError, Result, ScalarValue, +}; +use datafusion_expr::utils::conjunction; +use datafusion_expr::{TableProviderFilterPushDown, TableType}; +use datafusion_physical_expr::utils::{Guarantee, LiteralGuarantee}; +use futures::future::BoxFuture; +use futures::FutureExt; +use object_store::ObjectStore; +use std::any::Any; +use std::collections::{HashMap, HashSet}; +use std::fs::File; +use std::ops::Range; +use std::path::{Path, PathBuf}; +use std::sync::atomic::{AtomicBool, Ordering}; +use std::sync::Arc; +use tempfile::TempDir; +use url::Url; + +/// This example demonstrates using low level DataFusion APIs to read only +/// certain row groups and ranges from parquet files, based on external +/// information. +/// +/// Using these APIs, you can instruct DataFusion's parquet reader to skip +/// ("prune") portions of files that do not contain relevant data. These APIs +/// can be useful for doing low latency queries over a large number of Parquet +/// files on remote storage (e.g. S3) where the cost of reading the metadata for +/// each file is high (e.g. because it requires a network round trip to the +/// storage service). +/// +/// Depending on the information from the index, DataFusion can make a request +/// to the storage service (e.g. S3) to read only the necessary data. +/// +/// Note that this example uses a hard coded index implementation. For a more +/// realistic example of creating an index to prune files, see the +/// `parquet_index.rs` example. +/// +/// Specifically, this example illustrates how to: +/// 1. Use [`ParquetFileReaderFactory`] to avoid re-reading parquet metadata on each query +/// 2. Use [`PruningPredicate`] for predicate analysis +/// 3. Pass a row group selection to [`ParuetExec`] +/// 4. Pass a row selection (within a row group) to [`ParuetExec`] +/// +/// Note this is a *VERY* low level example for people who want to build their +/// own custom indexes (e.g. for low latency queries). Most users should use +/// higher level APIs for reading parquet files: +/// [`SessionContext::read_parquet`] or [`ListingTable`], which also do file +/// pruning based on parquet statistics (using the same underlying APIs) +/// +/// # Diagram Review Comment: I added a diagram here to try and explain what is going on visually for those so inclined -- 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: github-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
