gruuya commented on code in PR #880: URL: https://github.com/apache/iceberg-rust/pull/880#discussion_r1905919573
########## crates/integrations/datafusion/src/statistics.rs: ########## @@ -0,0 +1,112 @@ +// 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 std::collections::HashMap; + +use datafusion::common::stats::Precision; +use datafusion::common::{ColumnStatistics, Statistics}; +use iceberg::spec::ManifestStatus; +use iceberg::table::Table; +use iceberg::Result; + +use crate::physical_plan::expr_to_predicate::datum_to_scalar_value; + +// Compute DataFusion table statistics for a given table/snapshot +pub async fn compute_statistics(table: &Table, snapshot_id: Option<i64>) -> Result<Statistics> { + let file_io = table.file_io(); + let metadata = table.metadata(); + let snapshot = table.snapshot(snapshot_id)?; + + let mut num_rows = 0; + let mut lower_bounds = HashMap::new(); + let mut upper_bounds = HashMap::new(); + let mut null_counts = HashMap::new(); + + let manifest_list = snapshot.load_manifest_list(file_io, metadata).await?; + + // For each existing/added manifest in the snapshot aggregate the row count, as well as null + // count and min/max values. + for manifest_file in manifest_list.entries() { + let manifest = manifest_file.load_manifest(file_io).await?; Review Comment: Thanks for the feedback, I greatly appreciate it. Regarding 1, I agree completely (and think it should be [done during table instantiation](https://github.com/apache/iceberg-rust/pull/880#discussion_r1904197220)), I mainly wanted to get some validation on the general approach first. (Perhaps it might also be an optional call via something like `IcebergTableProvider::with_statistics`, which would be chained after one of the existing construction methods.) As for point 2, is it not sufficient that I aggregate stats only for `manifest_entry.status() != ManifestStatus::Deleted` below? Put another way is it possible for `ManifestStatus::Existing | ManifestStatus::Added` entries to contain some misleading stats? Finally, while I think exposing the spec (puffin) statistics should definitely be implemented, it seems that this is not always available (it may be opt-in for some external writers such as pyiceberg/spark?), so the best course of action for starters is to gather the stats from the manifest (entries) by default. -- 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: issues-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
