Changeset: c47cfa18f023 for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/c47cfa18f023
Modified Files:
sql/server/rel_statistics.c
Branch: properties
Log Message:
Tunning cardinality estimation for distinct projections and single joins
diffs (155 lines):
diff --git a/sql/server/rel_statistics.c b/sql/server/rel_statistics.c
--- a/sql/server/rel_statistics.c
+++ b/sql/server/rel_statistics.c
@@ -604,12 +604,36 @@ trivial_project_exp_card(sql_exp *e)
return e->type == e_atom && e->f ? (BUN) list_length(e->f) : 1;
}
+static BUN
+rel_calc_nuniques(sql_rel *rel, sql_rel *l, list *exps)
+{
+ BUN nuniques = 0;
+
+ /* compute the highest number of unique values */
+ if (!list_empty(exps)) {
+ for (node *n = exps->h ; n && nuniques != BUN_NONE ; n =
n->next) {
+ sql_exp *e = n->data;
+ sql_rel *bt = NULL;
+ prop *p = NULL;
+
+ if (e->type == e_column && is_unique(e) &&
+ name_find_column(rel, e->l, e->r, -1, &bt) &&
bt && (p = find_prop(bt->p, PROP_COUNT))) {
+ nuniques = MAX(nuniques, p->value.lval);
+ } else if ((p = find_prop(e->p, PROP_NUNIQUES))) {
+ nuniques = MAX(nuniques, (BUN) p->value.dval);
+ } else {
+ nuniques = BUN_NONE;
+ }
+ }
+ }
+ return nuniques != BUN_NONE ? nuniques : get_rel_count(l);
+}
+
static sql_rel *
rel_get_statistics_(visitor *v, sql_rel *rel)
{
/* Don't prune updates as pruning will possibly result in removing the
joins which therefore cannot be used for constraint checking */
uint8_t has_special_modify = *(uint8_t*) v->data;
- prop *p;
bool can_be_pruned = !has_special_modify && v->storage_based_opt;
/* Don't look at the same relation twice */
@@ -635,34 +659,33 @@ rel_get_statistics_(visitor *v, sql_rel
case op_except: {
bool empty_cross = false;
int i = 0;
- sql_rel *l = rel->l, *r = rel->r;
+ sql_rel *l = rel->l, *pl = rel->l, *r = rel->r, *pr = rel->r;
- while (is_sample(l->op) || is_topn(l->op)) /* skip topN and
sample relations in the middle */
- l = l->l;
- while (is_sample(r->op) || is_topn(r->op))
- r = r->l;
+ while (is_sample(pl->op) || is_topn(pl->op)) /* skip topN and
sample relations in the middle */
+ pl = pl->l;
+ while (is_sample(r->op) || is_topn(pr->op))
+ pr = pr->l;
/* if it's not a projection, then project and propagate
statistics */
- if (!is_project(l->op) && !is_base(l->op)) {
- l = rel_project(v->sql->sa, l, rel_projections(v->sql,
l, NULL, 0, 1));
- set_count_prop(v->sql->sa, l, get_rel_count(l->l));
- l->exps = exps_exp_visitor_bottomup(v, l, l->exps, 0,
&rel_propagate_statistics, false);
+ if (!is_project(pl->op) && !is_base(l->op)) {
+ pl = rel_project(v->sql->sa, pl,
rel_projections(v->sql, pl, NULL, 0, 1));
+ set_count_prop(v->sql->sa, pl, get_rel_count(pl->l));
+ pl->exps = exps_exp_visitor_bottomup(v, pl, pl->exps,
0, &rel_propagate_statistics, false);
}
- if (!is_project(r->op) && !is_base(r->op)) {
- r = rel_project(v->sql->sa, r, rel_projections(v->sql,
r, NULL, 0, 1));
- set_count_prop(v->sql->sa, r, get_rel_count(r->l));
- r->exps = exps_exp_visitor_bottomup(v, r, r->exps, 0,
&rel_propagate_statistics, false);
+ if (!is_project(pr->op) && !is_base(pr->op)) {
+ pr = rel_project(v->sql->sa, pr,
rel_projections(v->sql, pr, NULL, 0, 1));
+ set_count_prop(v->sql->sa, pr, get_rel_count(pr->l));
+ pr->exps = exps_exp_visitor_bottomup(v, pr, pr->exps,
0, &rel_propagate_statistics, false);
}
for (node *n = rel->exps->h ; n ; n = n->next) {
- empty_cross |= rel_setop_get_statistics(v->sql, rel,
l->exps, r->exps, n->data, i);
+ empty_cross |= rel_setop_get_statistics(v->sql, rel,
pl->exps, pr->exps, n->data, i);
i++;
}
- l = rel->l;
- r = rel->r;
/* propagate row count */
if (is_union(rel->op)) {
- BUN lv = get_rel_count(l), rv = get_rel_count(r);
+ BUN lv = need_distinct(rel) ? rel_calc_nuniques(rel,
pl, pl->exps) : get_rel_count(pl),
+ rv = need_distinct(rel) ?
rel_calc_nuniques(rel, pr, pr->exps) : get_rel_count(pr);
if (lv == 0 && rv == 0) { /* both sides empty */
if (can_be_pruned)
@@ -677,7 +700,8 @@ rel_get_statistics_(visitor *v, sql_rel
set_count_prop(v->sql->sa, rel, (rv > (BUN_MAX
- lv)) ? BUN_MAX : (lv + rv)); /* overflow check */
}
} else if (is_inter(rel->op) || is_except(rel->op)) {
- BUN lv = get_rel_count(l), rv = get_rel_count(r);
+ BUN lv = need_distinct(rel) ? rel_calc_nuniques(rel,
pl, pl->exps) : get_rel_count(pl),
+ rv = need_distinct(rel) ?
rel_calc_nuniques(rel, pr, pr->exps) : get_rel_count(pr);
if (lv == 0) { /* left side empty */
if (can_be_pruned)
@@ -744,7 +768,7 @@ rel_get_statistics_(visitor *v, sql_rel
case op_full: {
BUN lv = get_rel_count(l), rv = get_rel_count(r),
uniques_estimate = BUN_MAX, join_idx_estimate = BUN_MAX;
- if (!list_empty(rel->exps)) {
+ if (!list_empty(rel->exps) && !is_single(rel)) {
for (node *n = rel->exps->h ; n ; n = n->next) {
sql_exp *e = n->data, *el = e->l, *er =
e->r;
@@ -764,7 +788,9 @@ rel_get_statistics_(visitor *v, sql_rel
}
}
}
- if (join_idx_estimate != BUN_MAX) {
+ if (is_single(rel)) {
+ set_count_prop(v->sql->sa, rel, lv);
+ } else if (join_idx_estimate != BUN_MAX) {
set_count_prop(v->sql->sa, rel,
join_idx_estimate);
} else if (uniques_estimate != BUN_MAX) {
set_count_prop(v->sql->sa, rel,
uniques_estimate);
@@ -803,7 +829,11 @@ rel_get_statistics_(visitor *v, sql_rel
} break;
case op_project: {
if (l) {
- set_count_prop(v->sql->sa, rel,
get_rel_count(l));
+ if (need_distinct(rel)) {
+ set_count_prop(v->sql->sa, rel,
rel_calc_nuniques(rel, l, rel->exps));
+ } else {
+ set_count_prop(v->sql->sa, rel,
get_rel_count(l));
+ }
} else {
BUN card = 1;
@@ -819,18 +849,8 @@ rel_get_statistics_(visitor *v, sql_rel
case op_groupby: {
if (list_empty(rel->r)) {
set_count_prop(v->sql->sa, rel, 1);
- } else if (list_length(rel->r) == 1) {
- sql_exp *e = ((list*)rel->r)->h->data;
- sql_rel *bt = NULL;
- if (e->type == e_column && is_unique(e) &&
name_find_column(rel, e->l, e->r, -1, &bt) && bt && (p = find_prop(bt->p,
PROP_COUNT))) {
- set_count_prop(v->sql->sa, rel,
p->value.lval);
- } else if ((p = find_prop(e->p,
PROP_NUNIQUES))) {
- set_count_prop(v->sql->sa, rel, (BUN)
p->value.dval);
- } else {
- set_count_prop(v->sql->sa, rel,
get_rel_count(l));
- }
} else {
- set_count_prop(v->sql->sa, rel,
get_rel_count(l));
+ set_count_prop(v->sql->sa, rel,
rel_calc_nuniques(rel, l, rel->r));
}
} break;
default:
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