sgrebnov commented on code in PR #13132:
URL: https://github.com/apache/datafusion/pull/13132#discussion_r1817953084
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datafusion/sql/src/unparser/utils.rs:
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@@ -239,6 +239,87 @@ pub(crate) fn unproject_sort_expr(
Ok(sort_expr)
}
+/// Iterates through the children of a [LogicalPlan] to find a TableScan node
before encountering
+/// a Projection or any unexpected node that indicates the presence of a
Projection (SELECT) in the plan.
+/// If a TableScan node is found, returns the TableScan node without filters,
along with the collected filters separately.
+/// If the plan contains a Projection, returns None.
+///
+/// Note: If a table alias is present, TableScan filters are rewritten to
reference the alias.
+///
+/// LogicalPlan example:
+/// Filter: ta.j1_id < 5
+/// Alias: ta
+/// TableScan: j1, j1_id > 10
+///
+/// Will return LogicalPlan below:
+/// Alias: ta
+/// TableScan: j1
+/// And filters: [ta.j1_id < 5, ta.j1_id > 10]
+pub(crate) fn try_transform_to_simple_table_scan_with_filters(
+ plan: &LogicalPlan,
+) -> Result<Option<(LogicalPlan, Vec<Expr>)>> {
+ let mut filters: Vec<Expr> = vec![];
+ let mut plan_stack = vec![plan];
+ let mut table_alias = None;
+
+ while let Some(current_plan) = plan_stack.pop() {
+ match current_plan {
+ LogicalPlan::SubqueryAlias(alias) => {
+ table_alias = Some(alias.alias.clone());
+ plan_stack.push(alias.input.as_ref());
+ }
+ LogicalPlan::Filter(filter) => {
+ filters.push(filter.predicate.clone());
+ plan_stack.push(filter.input.as_ref());
+ }
+ LogicalPlan::TableScan(table_scan) => {
+ let table_schema = table_scan.source.schema();
+ // optional rewriter if table has an alias
+ let mut filter_alias_rewriter =
+ table_alias.as_ref().map(|alias_name| TableAliasRewriter {
+ table_schema: &table_schema,
+ alias_name: alias_name.clone(),
+ });
+
+ // rewrite filters to use table alias if present
+ let table_scan_filters = table_scan
Review Comment:
`unparse_table_scan_pushdown` has similar filters rewriting logic (other
logic is different as it adds filters directly to new plan) - this could be
refactored to re-use some common rewrite logic
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