Changeset: ef30e857ad20 for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/ef30e857ad20
Modified Files:
sql/server/rel_optimizer.c
Branch: antipush
Log Message:
Added push select up optimization.
This optimization will run once after all other relational optimizations to
avoid infinite optimization loops with push ups and push downs.
diffs (79 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
@@ -4737,6 +4737,64 @@ rel_push_join_exps_down(visitor *v, sql_
return rel;
}
+static bool
+point_select_on_unique_column(sql_rel *rel)
+{
+ if (is_select(rel->op) && !list_empty(rel->exps)) {
+ for (node *n = rel->exps->h; n ; n = n->next) {
+ sql_exp *e = n->data, *el = e->l, *er = e->r, *found =
NULL;
+
+ if (is_compare(e->type) && e->flag == cmp_equal) {
+ if (is_numeric_upcast(el))
+ el = el->l;
+ if (is_alias(el->type) && exp_is_atom(er) &&
(found = rel_find_exp(rel->l, el)) &&
+ is_unique(found) && (!is_semantics(e)
|| !has_nil(el) || !has_nil(er)))
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
+/*
+ * A point select on an unique column reduces the number of rows to 1. If the
same select is under a
+ * join, the opposite side's select can be pushed above the join.
+ */
+static sql_rel *
+rel_push_select_up(visitor *v, sql_rel *rel)
+{
+ if ((is_join(rel->op) || is_semi(rel->op)) && !rel_is_ref(rel)) {
+ sql_rel *l = rel->l, *r = rel->r;
+ bool can_pushup_left = is_select(l->op) && !rel_is_ref(l),
+ can_pushup_right = is_select(r->op) && !rel_is_ref(r)
&& !is_semi(rel->op);
+
+ if (can_pushup_left || can_pushup_right) {
+ if (can_pushup_left)
+ can_pushup_left =
point_select_on_unique_column(r);
+ if (can_pushup_right)
+ can_pushup_right =
point_select_on_unique_column(l);
+
+ /* if both selects retrieve one row each, it's not
worth it to push both up */
+ if (can_pushup_left && !can_pushup_right) {
+ sql_rel *ll = l->l;
+ rel->l = ll;
+ l->l = rel;
+ rel = l;
+ assert(is_select(rel->op));
+ v->changes++;
+ } else if (!can_pushup_left && can_pushup_right) {
+ sql_rel *rl = r->l;
+ rel->r = rl;
+ r->l = rel;
+ rel = r;
+ assert(is_select(rel->op));
+ v->changes++;
+ }
+ }
+ }
+ return rel;
+}
+
/*
* Push {semi}joins down, pushes the joins through group by expressions.
* When the join is on the group by columns, we can push the joins left
@@ -9751,5 +9809,10 @@ rel_optimizer(mvc *sql, sql_rel *rel, in
#ifndef NDEBUG
assert(level < 20);
#endif
+ /* Run the following optimizers only once after the others run to avoid
an infinite optimization loop */
+ gp = (global_props) {.cnt = {0},};
+ rel_properties(sql, &gp, rel); /* collect relational tree properties */
+ if ((gp.cnt[op_join] || gp.cnt[op_left] || gp.cnt[op_right] ||
gp.cnt[op_full] || gp.cnt[op_semi] || gp.cnt[op_anti]) && gp.cnt[op_select])
+ rel = rel_visitor_bottomup(&v, rel, &rel_push_select_up);
return rel;
}
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