Changeset: 842feff7722a for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=842feff7722a
Modified Files:
sql/server/rel_optimizer.c
sql/server/rel_unnest.c
Branch: Jun2020
Log Message:
Small fixes for rel_join2semijoin optimizer.
Disallow rel_join2semijoin on selection relations, because upper projections
may use the right side of the semijoin.
Only e_columns are allowed as the single projection under the candidate join
(e.g. aggregates may not be distinct). A better way to fix this would be adding
an "unique" property under SQL expressions.
Fixed grouping cardinalities at exp_reset_card.
diffs (53 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
@@ -5452,11 +5452,14 @@ find_simple_projection_for_join2semi(sql
if (rel->card < CARD_AGGR) /* const or groupby without group by
exps */
return true;
- if (e->card <= CARD_AGGR || find_prop(e->p, PROP_HASHCOL))
- return true;
- sql_exp *found = rel_find_exp(rel->l, e); /* grouping column on
inner relation */
- if (found && (found->card <= CARD_AGGR || find_prop(found->p,
PROP_HASHCOL)))
- return true;
+ /* a single group by column in the projection list from a group
by relation is guaranteed to be unique, but not an aggregate */
+ if (e->type == e_column) {
+ if (is_groupby(rel->op) || find_prop(e->p,
PROP_HASHCOL))
+ return true;
+ sql_exp *found = rel_find_exp(rel->l, e); /* grouping
column on inner relation */
+ if (found && ((found->type == e_column && found->card
<= CARD_AGGR) || find_prop(found->p, PROP_HASHCOL)))
+ return true;
+ }
}
return false;
}
@@ -5524,7 +5527,7 @@ static sql_rel *
rel_join2semijoin(mvc *sql, sql_rel *rel, int *changes)
{
(void)sql;
- if ((is_simple_project(rel->op) || is_groupby(rel->op) ||
(is_select(rel->op) && !rel_is_ref(rel))) && rel->l) {
+ if ((is_simple_project(rel->op) || is_groupby(rel->op)) && rel->l) {
bool swap = false;
sql_rel *l = rel->l;
sql_rel *c = find_candidate_join2semi(l, &swap);
diff --git a/sql/server/rel_unnest.c b/sql/server/rel_unnest.c
--- a/sql/server/rel_unnest.c
+++ b/sql/server/rel_unnest.c
@@ -1652,7 +1652,7 @@ exp_reset_card(mvc *sql, sql_rel *rel, s
switch(e->type) {
case e_aggr:
case e_column:
- e->card = CARD_AGGR;
+ e->card = rel->card;
break;
case e_func:
case e_convert:
@@ -1673,6 +1673,8 @@ exp_reset_card(mvc *sql, sql_rel *rel, s
l = rel->l;
if (e->card < l->card)
e->card = l->card;
+ if (need_distinct(rel)) /* Need distinct, all expressions
should have CARD_AGGR at max */
+ e->card = MIN(e->card, CARD_AGGR);
break;
case e_aggr: /* should have been corrected by rewrites already */
case e_cmp:
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