[GitHub] [arrow-datafusion] Dandandan commented on a change in pull request #365: Refactor: move RowGroupPredicateBuilder into its own module, rename to PruningPredicateBuilder

[GitBox <gi...@apache.org>]

Dandandan commented on a change in pull request #365:
URL: https://github.com/apache/arrow-datafusion/pull/365#discussion_r635552829



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File path: datafusion/src/physical_optimizer/pruning.rs
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@@ -0,0 +1,769 @@
+// 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.
+
+//! This module contains code to rule out row groups / partitions /
+//! etc based on statistics prior in order to skip evaluating entire
+//! swaths of rows.
+//!
+//! This code is currently specific to Parquet, but soon (TM), via
+//! https://github.com/apache/arrow-datafusion/issues/363 it will
+//! be genericized.
+
+use std::{collections::HashSet, sync::Arc};
+
+use arrow::{
+    array::{
+        make_array, new_null_array, ArrayData, ArrayRef, BooleanArray,
+        BooleanBufferBuilder,
+    },
+    buffer::MutableBuffer,
+    datatypes::{DataType, Field, Schema},
+    record_batch::RecordBatch,
+};
+
+use parquet::file::{
+    metadata::RowGroupMetaData, statistics::Statistics as ParquetStatistics,
+};
+
+use crate::{
+    error::{DataFusionError, Result},
+    execution::context::ExecutionContextState,
+    logical_plan::{Expr, Operator},
+    optimizer::utils,
+    physical_plan::{planner::DefaultPhysicalPlanner, ColumnarValue, PhysicalExpr},
+};
+
+#[derive(Debug, Clone)]
+/// Builder used for generating predicate functions that can be used
+/// to prune data based on statistics (e.g. parquet row group metadata)
+pub struct PruningPredicateBuilder {
+    schema: Schema,
+    predicate_expr: Arc<dyn PhysicalExpr>,
+    stat_column_req: Vec<(String, StatisticsType, Field)>,
+}
+
+impl PruningPredicateBuilder {
+    /// Try to create a new instance of [`PruningPredicateBuilder`]
+    ///
+    /// This will translate the filter expression into a statistics predicate expression
+    ///
+    /// For example,  `(column / 2) = 4` becomes `(column_min / 2) <= 4 && 4 <= (column_max / 2))`
+    pub fn try_new(expr: &Expr, schema: Schema) -> Result<Self> {
+        // build predicate expression once
+        let mut stat_column_req = Vec::<(String, StatisticsType, Field)>::new();
+        let logical_predicate_expr =
+            build_predicate_expression(expr, &schema, &mut stat_column_req)?;
+        // println!(
+        //     "PruningPredicateBuilder::try_new, logical_predicate_expr: {:?}",

Review comment:
       Those println comments could be removed?




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