Changeset: 744fde31e79c for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=744fde31e79c
Modified Files:
sql/server/rel_optimizer.c
Branch: Oct2020
Log Message:
A projection doesn't change the input cardinality for an union.
rel_push_project_down_union optimization is allowed on that case
diffs (21 lines):
diff --git a/sql/server/rel_optimizer.c b/sql/server/rel_optimizer.c
--- a/sql/server/rel_optimizer.c
+++ b/sql/server/rel_optimizer.c
@@ -5628,7 +5628,7 @@ rel_push_project_down_union(visitor *v,
sql_rel *ul = u->l;
sql_rel *ur = u->r;
- if (!u || !is_union(u->op) || need_distinct(u) || is_single(u)
|| !u->exps || rel_is_ref(u) || project_unsafe(rel,0))
+ if (!u || !is_union(u->op) || need_distinct(u) || !u->exps ||
rel_is_ref(u) || project_unsafe(rel,0))
return rel;
/* don't push project down union of single values */
if ((is_project(ul->op) && !ul->l) || (is_project(ur->op) &&
!ur->l))
@@ -5664,6 +5664,8 @@ rel_push_project_down_union(visitor *v,
rel_projections(v->sql, rel, NULL, 1, 1));
if (need_distinct)
set_distinct(rel);
+ if (is_single(u))
+ set_single(rel);
v->changes++;
rel->l = rel_merge_projects(v, rel->l);
rel->r = rel_merge_projects(v, rel->r);
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