itsjunetime commented on code in PR #12135:
URL: https://github.com/apache/datafusion/pull/12135#discussion_r1737065470
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datafusion/core/src/datasource/physical_plan/parquet/row_filter.rs:
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@@ -268,90 +259,183 @@ impl<'a> FilterCandidateBuilder<'a> {
/// * `Ok(Some(candidate))` if the expression can be used as an ArrowFilter
/// * `Ok(None)` if the expression cannot be used as an ArrowFilter
/// * `Err(e)` if an error occurs while building the candidate
- pub fn build(
- mut self,
- metadata: &ParquetMetaData,
- ) -> Result<Option<FilterCandidate>> {
- let expr = self.expr.clone().rewrite(&mut self).data()?;
-
- if self.non_primitive_columns || self.projected_columns {
- Ok(None)
- } else {
- let required_bytes =
- size_of_columns(&self.required_column_indices, metadata)?;
- let can_use_index = columns_sorted(&self.required_column_indices,
metadata)?;
-
- Ok(Some(FilterCandidate {
- expr,
- required_bytes,
- can_use_index,
- projection: self.required_column_indices.into_iter().collect(),
- }))
+ pub fn build(self, metadata: &ParquetMetaData) ->
Result<Option<FilterCandidate>> {
+ let Some((projection, rewritten_expr)) = non_pushdown_columns(
+ Arc::clone(&self.expr),
+ self.file_schema,
+ self.table_schema,
+ )?
+ else {
+ return Ok(None);
+ };
+
+ let required_bytes = size_of_columns(&self.required_column_indices,
metadata)?;
+ let can_use_index = columns_sorted(&self.required_column_indices,
metadata)?;
+
+ Ok(Some(FilterCandidate {
+ expr: rewritten_expr,
+ required_bytes,
+ can_use_index,
+ projection,
+ }))
+ }
+}
+
+// a struct that implements TreeNodeRewriter to traverse a PhysicalExpr tree
structure to determine
+// if any column references in the expression would prevent it from being
predicate-pushed-down.
+// if non_primitive_columns || projected_columns, it can't be pushed down.
+// can't be reused between calls to `rewrite`; each construction must be used
only once.
+struct PushdownChecker<'schema> {
+ /// Does the expression require any non-primitive columns (like structs)?
+ non_primitive_columns: bool,
+ /// Does the expression reference any columns that are in the table
+ /// schema but not in the file schema?
+ projected_columns: bool,
+ // the indices of all the columns found within the given expression which
exist inside the given
+ // [`file_schema`]
+ required_column_indices: BTreeSet<usize>,
+ file_schema: &'schema Schema,
+ table_schema: &'schema Schema,
+}
+
+impl<'schema> PushdownChecker<'schema> {
+ fn check_single_column(&mut self, column_name: &str) ->
Option<TreeNodeRecursion> {
Review Comment:
I made this into an associated function so that it can be used by itself or
as a part of `PushdownChecker`'s tree node recursion functions. It sets some
things on the `PushdownChecker` that are needed to track projected columns, so
I guess we could make it a free function, but then it would still need to pass
in all the fields of `PushdownChecker` to do all it needs to do, thus negating
the benefits of being a free function.
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