xudong963 commented on code in PR #3170: URL: https://github.com/apache/arrow-rs/pull/3170#discussion_r1031396521
########## parquet/examples/async_read_parquet.rs: ########## @@ -0,0 +1,63 @@ +// 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::util::pretty::print_batches; +use futures::TryStreamExt; +use parquet::arrow::arrow_reader::{ArrowPredicate, RowFilter}; +use parquet::arrow::{ParquetRecordBatchStreamBuilder, ProjectionMask}; +use parquet::errors::Result; +use std::time::SystemTime; +use tokio::fs::File; + +#[tokio::main(flavor = "current_thread")] +async fn main() -> Result<()> { + // Create parquet file that will be read. + let testdata = arrow::util::test_util::parquet_test_data(); + let path = format!("{}/alltypes_plain.parquet", testdata); + let file = File::open(path).await.unwrap(); + + // Create a async parquet reader builder with batch_size. + // batch_size is the number of rows to read up to buffer once from pages, defaults to 1024 + let mut builder = ParquetRecordBatchStreamBuilder::new(file) + .await + .unwrap() + .with_batch_size(8192); + let file_metadata = builder.metadata().file_metadata(); + + let mask = ProjectionMask::roots(file_metadata.schema_descr(), [1, 2]); + // Set projection mask to read only leaf columns 1 and 2. + builder = builder.with_projection(mask); + + // Highlight: set `RowFilter`, it'll push down filter predicates to skip IO and decode. + // For more specific usage: please refer to https://github.com/apache/arrow-datafusion/blob/master/datafusion/core/src/physical_plan/file_format/parquet/row_filter.rs. + let predicates: Vec<Box<dyn ArrowPredicate>> = Vec::new(); Review Comment: Ok (failure to be lazy 🤣 ) -- 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]
