From 3214287a5f93bdfb5f43c2cd63117af4dac6ae7a Mon Sep 17 00:00:00 2001
From: Andrew Duffy <andreweduffy@gmail.com>
Date: Tue, 25 Jun 2024 08:52:36 -0400
Subject: [PATCH] save

---
 vortex-datafusion/src/lib.rs | 100 ++++++++++++++++++++++++++++++++---
 1 file changed, 94 insertions(+), 6 deletions(-)

diff --git a/vortex-datafusion/src/lib.rs b/vortex-datafusion/src/lib.rs
index ba7330848f..6361d36869 100644
--- a/vortex-datafusion/src/lib.rs
+++ b/vortex-datafusion/src/lib.rs
@@ -9,13 +9,20 @@ use std::task::{Context, Poll};
 use arrow_array::{RecordBatch, StructArray as ArrowStructArray};
 use arrow_schema::SchemaRef;
 use async_trait::async_trait;
+use datafusion::arrow::buffer::NullBuffer;
 use datafusion::dataframe::DataFrame;
 use datafusion::datasource::TableProvider;
 use datafusion::execution::context::SessionState;
 use datafusion::execution::{RecordBatchStream, SendableRecordBatchStream, TaskContext};
+use datafusion::optimizer::simplify_expressions::ExprSimplifier;
 use datafusion::prelude::SessionContext;
-use datafusion_common::{exec_datafusion_err, exec_err, DataFusionError, Result as DFResult};
-use datafusion_expr::{Expr, TableProviderFilterPushDown, TableType};
+use datafusion_common::{
+    exec_datafusion_err, DataFusionError, Result as DFResult, ScalarValue, ToDFSchema,
+};
+use datafusion_common::tree_node::{TreeNodeRecursion, TreeNodeVisitor};
+use datafusion_expr::execution_props::ExecutionProps;
+use datafusion_expr::simplify::SimplifyContext;
+use datafusion_expr::{BinaryExpr, Expr, Operator, TableProviderFilterPushDown, TableType};
 use datafusion_physical_expr::EquivalenceProperties;
 use datafusion_physical_plan::{
     DisplayAs, DisplayFormatType, ExecutionMode, ExecutionPlan, Partitioning, PlanProperties,
@@ -99,9 +106,16 @@ impl TableProvider for VortexInMemoryTableProvider {
         filters: &[Expr],
         _limit: Option<usize>,
     ) -> DFResult<Arc<dyn ExecutionPlan>> {
-        if !filters.is_empty() {
-            return exec_err!("vortex does not support filter pushdown");
-        }
+        let filter_expr = if filters.is_empty() {
+            None
+        } else {
+            Some(make_simplified_conjunction(
+                filters,
+                self.schema_ref.clone(),
+            )?)
+        };
+
+        println!("simplified filter: {filter_expr:?}");
 
         let partitioning = if let Ok(chunked_array) = ChunkedArray::try_from(&self.array) {
             Partitioning::RoundRobinBatch(chunked_array.nchunks())
@@ -118,6 +132,7 @@ impl TableProvider for VortexInMemoryTableProvider {
         Ok(Arc::new(VortexMemoryExec {
             array: self.array.clone(),
             projection: projection.cloned(),
+            filter_expr,
             plan_properties,
         }))
     }
@@ -129,15 +144,88 @@ impl TableProvider for VortexInMemoryTableProvider {
         // TODO(aduffy): add support for filter pushdown
         Ok(filters
             .iter()
-            .map(|_| TableProviderFilterPushDown::Unsupported)
+            .map(|expr| {
+                match expr {
+                    // Several expressions can be pushed down.
+                    Expr::BinaryExpr(_)
+                    | Expr::IsNotNull(_)
+                    | Expr::IsNull(_)
+                    | Expr::IsTrue(_)
+                    | Expr::IsFalse(_)
+                    | Expr::IsNotTrue(_)
+                    | Expr::IsNotFalse(_)
+                    | Expr::Cast(_) => TableProviderFilterPushDown::Exact,
+
+                    // All other expressions should be handled outside of the TableProvider
+                    // via the normal DataFusion operator chain.
+                    _ => TableProviderFilterPushDown::Unsupported,
+                }
+
+                TableProviderFilterPushDown::Exact
+            })
             .collect())
     }
 }
 
+struct ValidationVisitor {}
+
+impl ValidationVisitor {
+
+}
+
+impl TreeNodeVisitor for ValidationVisitor {
+    type Node = Expr;
+
+    fn f_down(&mut self, node: &Self::Node) -> DFResult<TreeNodeRecursion> {
+
+    }
+}
+
+/// A mask determining the rows in an Array that should be treated as valid for query processing.
+/// The vector is used to determine the take order of a set of things, or otherwise we determine
+/// that we want to perform cross-filtering of the larger columns, if we so choose.
+pub(crate) struct RowSelection {
+    selection: NullBuffer,
+}
+
+/// Convert a set of expressions that must all match into a single AND expression.
+///
+/// # Returns
+///
+/// If conversion is successful, the result will be a
+/// [binary expression node][datafusion_expr::Expr::BinaryExpr] containing the conjunction.
+///
+/// Note that the set of operators must be provided here instead.
+///
+/// # Simplification
+///
+/// Simplification will occur as part of this process, so constant folding and similar optimizations
+/// will be applied before returning the final expression.
+fn make_simplified_conjunction(filters: &[Expr], schema: SchemaRef) -> DFResult<Expr> {
+    let init = Box::new(Expr::Literal(ScalarValue::Boolean(Some(true))));
+    let conjunction = filters.iter().fold(init, |conj, item| {
+        Box::new(Expr::BinaryExpr(BinaryExpr::new(
+            conj,
+            Operator::And,
+            Box::new(item.clone()),
+        )))
+    });
+
+    let schema = schema.to_dfschema_ref()?;
+
+    // simplify the expression.
+    let props = ExecutionProps::new();
+    let context = SimplifyContext::new(&props).with_schema(schema);
+    let simplifier = ExprSimplifier::new(context);
+
+    simplifier.simplify(*conjunction)
+}
+
 /// Physical plan node for scans against an in-memory, possibly chunked Vortex Array.
 #[derive(Debug, Clone)]
 struct VortexMemoryExec {
     array: Array,
+    filter_expr: Option<Expr>,
     projection: Option<Vec<usize>>,
     plan_properties: PlanProperties,
 }