xudong963 commented on code in PR #15787:
URL: https://github.com/apache/datafusion/pull/15787#discussion_r2052289117
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datafusion/optimizer/src/optimize_projections/mod.rs:
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@@ -785,13 +785,24 @@ fn rewrite_projection_given_requirements(
/// Projection is unnecessary, when
/// - input schema of the projection, output schema of the projection are
same, and
/// - all projection expressions are either Column or Literal
-fn is_projection_unnecessary(input: &LogicalPlan, proj_exprs: &[Expr]) ->
Result<bool> {
- // First check if all expressions are trivial (cheaper operation than
`projection_schema`)
- if !proj_exprs.iter().all(is_expr_trivial) {
+pub fn is_projection_unnecessary(
+ input: &LogicalPlan,
+ proj_exprs: &[Expr],
+) -> Result<bool> {
+ // First check if the number of expressions is equal to the number of
fields in the input schema.
+ if proj_exprs.len() != input.schema().fields().len() {
return Ok(false);
}
- let proj_schema = projection_schema(input, proj_exprs)?;
- Ok(&proj_schema == input.schema())
+ Ok(input.schema().iter().zip(proj_exprs.iter()).all(
+ |((field_relation, field_name), expr)| {
+ // Check if the expression is a column and if it matches the field
name
+ if let Expr::Column(col) = expr {
Review Comment:
The method is used to check if the `projection` can be removed, if the expr
in projection isn't column, I think the projection should be retained.
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