jayzhan211 commented on code in PR #13134:
URL: https://github.com/apache/datafusion/pull/13134#discussion_r1819112939
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datafusion/optimizer/src/decorrelate_predicate_subquery.rs:
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@@ -296,37 +287,26 @@ fn build_join_top(
///
/// ```text
/// Projection: t1.id
-/// Filter: t1.id < 0 OR __correlated_sq_1.__exists IS NOT NULL
-/// Left Join: Filter: t1.id = __correlated_sq_1.id
+/// Filter: t1.id < 0 OR __correlated_sq_1.mark
+/// LeftMark Join: Filter: t1.id = __correlated_sq_1.id
/// TableScan: t1
/// SubqueryAlias: __correlated_sq_1
-/// Projection: t2.id, true as __exists
+/// Projection: t2.id
/// TableScan: t2
-fn existence_join(
+fn mark_join(
left: &LogicalPlan,
subquery: Arc<LogicalPlan>,
in_predicate_opt: Option<Expr>,
negated: bool,
alias_generator: &Arc<AliasGenerator>,
) -> Result<Option<(LogicalPlan, Expr)>> {
- // Add non nullable column to emulate existence join
- let always_true_expr = lit(true).alias("__exists");
- let cols = chain(
- subquery.schema().columns().into_iter().map(Expr::Column),
- iter::once(always_true_expr),
- );
- let subquery = LogicalPlanBuilder::from(subquery).project(cols)?.build()?;
let alias = alias_generator.next("__correlated_sq");
- let exists_col = Expr::Column(Column::new(Some(alias.clone()),
"__exists"));
- let exists_expr = if negated {
- exists_col.is_null()
- } else {
- exists_col.is_not_null()
- };
+ let exists_col = Expr::Column(Column::new(Some(alias.clone()), "mark"));
Review Comment:
Also here.
It seems the column has prefix `__` for `__exists` too. I think what
@jonahgao said makes sense. At least is more consistent with internal plan/expr
naming
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