yonatan-sevenai commented on code in PR #21593:
URL: https://github.com/apache/datafusion/pull/21593#discussion_r3100818826
##########
datafusion/sql/src/unparser/plan.rs:
##########
@@ -376,29 +406,112 @@ impl Unparser<'_> {
.select_to_sql_recursively(&new_plan, query, select,
relation);
}
- // Projection can be top-level plan for unnest relation
- // The projection generated by the `RecursiveUnnestRewriter`
from a UNNEST relation will have
- // only one expression, which is the placeholder column
generated by the rewriter.
- let unnest_input_type = if p.expr.len() == 1 {
- Self::check_unnest_placeholder_with_outer_ref(&p.expr[0])
- } else {
- None
- };
+ // Projection can be top-level plan for unnest relation.
+ // The projection generated by the `RecursiveUnnestRewriter`
+ // will have at least one expression referencing an unnest
+ // placeholder column.
+ let unnest_input_type: Option<UnnestInputType> =
+ p.expr.iter().find_map(Self::find_unnest_placeholder);
+
+ // --- UNNEST table factor path (BigQuery, etc.) ---
+ // Only fires for a single bare-placeholder projection.
+ // Uses peel_to_unnest_with_modifiers (rather than matching
+ // p.input directly) to handle Limit/Sort between Projection
+ // and Unnest.
if self.dialect.unnest_as_table_factor()
- && unnest_input_type.is_some()
- && let LogicalPlan::Unnest(unnest) = &p.input.as_ref()
+ && p.expr.len() == 1
+ && Self::is_bare_unnest_placeholder(&p.expr[0])
+ && let Some((unnest, unnest_plan)) =
+ self.peel_to_unnest_with_modifiers(p.input.as_ref(),
query)?
&& let Some(unnest_relation) =
self.try_unnest_to_table_factor_sql(unnest)?
{
relation.unnest(unnest_relation);
return self.select_to_sql_recursively(
- p.input.as_ref(),
+ unnest_plan,
query,
select,
relation,
);
}
+ // --- Snowflake LATERAL FLATTEN path ---
+ // `peel_to_unnest_with_modifiers` walks through any
+ // intermediate Limit/Sort nodes (the optimizer can insert
+ // these between the Projection and the Unnest), applies
+ // their modifiers to the query, and returns the Unnest +
+ // the LogicalPlan ref to recurse into. This bypasses the
+ // normal Limit/Sort handlers which would wrap the subtree
+ // in a derived subquery.
+ // SELECT rendering is delegated to
+ // `reconstruct_select_statement`, which rewrites
+ // placeholder columns to `"_unnest"."VALUE"` via
+ // `unproject_unnest_expr_as_flatten_value` — this works
+ // for bare, wrapped, and multi-expression projections.
+ if self.dialect.unnest_as_lateral_flatten()
+ && unnest_input_type.is_some()
+ && let Some((unnest, unnest_plan)) =
+ self.peel_to_unnest_with_modifiers(p.input.as_ref(),
query)?
+ && let Some(flatten) =
+ self.try_unnest_to_lateral_flatten_sql(unnest)?
+ {
+ let inner_projection =
+ Self::peel_to_inner_projection(unnest.input.as_ref())
+ .ok_or_else(|| {
+ DataFusionError::Internal(format!(
+ "Unnest input is not a Projection: {:?}",
+ unnest.input
+ ))
+ })?;
+
+ // An outer plan (e.g. a wrapping Projection) may have
+ // already set SELECT columns; only set them once.
+ if !select.already_projected() {
+ self.reconstruct_select_statement(plan, p, select)?;
+ }
+
+ if matches!(
+ inner_projection.input.as_ref(),
+ LogicalPlan::EmptyRelation(_)
+ ) {
+ // Inline array (e.g. UNNEST([1,2,3])):
+ // FLATTEN is the sole FROM source.
+ relation.flatten(flatten);
+ return self.select_to_sql_recursively(
+ unnest_plan,
+ query,
+ select,
+ relation,
+ );
+ }
+
+ // Non-empty source (table, subquery, etc.):
+ // recurse to set the primary FROM, then attach FLATTEN
+ // as a CROSS JOIN.
+ self.select_to_sql_recursively(unnest_plan, query, select,
relation)?;
+
+ let flatten_factor = flatten.build().map_err(|e| {
+ DataFusionError::Internal(format!("Failed to build
FLATTEN: {e}"))
Review Comment:
Thanks!
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