Changeset: 8c4d80b0600e for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=8c4d80b0600e
Modified Files:
sql/server/rel_optimizer.c
sql/server/rel_rewriter.c
sql/server/rel_rewriter.h
Branch: default
Log Message:
Embed rel_remove_empty_select optimizer changes on the optimizers it runs on to
avoid an extra AST iteration whenever empty selects/joins are generated
diffs (267 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
@@ -4468,6 +4468,9 @@ rel_push_groupby_down(visitor *v, sql_re
/*
* Push select down, pushes the selects through (simple) projections. Also
* it cleans up the projections which become useless.
+ *
+ * WARNING - Make sure to call try_remove_empty_select macro before returning
so we ensure
+ * possible generated empty selects will get removed without the need to call
rel_remove_empty_select optimizer
*/
static sql_rel *
rel_push_select_down(visitor *v, sql_rel *rel)
@@ -4490,8 +4493,8 @@ rel_push_select_down(visitor *v, sql_rel
}
/* don't make changes for empty selects */
- if (is_select(rel->op) && (!rel->exps || list_length(rel->exps) == 0))
- return rel;
+ if (is_select(rel->op) && list_empty(rel->exps))
+ return try_remove_empty_select(v, rel);
/* merge 2 selects */
r = rel->l;
@@ -4500,7 +4503,7 @@ rel_push_select_down(visitor *v, sql_rel
rel->l = NULL;
rel_destroy(rel);
v->changes++;
- return rel_push_select_down(v, r);
+ return try_remove_empty_select(v, r);
}
/*
* Push select through semi/anti join
@@ -4534,8 +4537,7 @@ rel_push_select_down(visitor *v, sql_rel
}
exps = rel->exps;
- if (rel->op == op_project &&
- r && r->op == op_project && !(rel_is_ref(r)))
+ if (rel->op == op_project && r && r->op == op_project &&
!(rel_is_ref(r)))
return rel_merge_projects(v, rel);
/* push select through join */
@@ -4592,38 +4594,35 @@ rel_push_select_down(visitor *v, sql_rel
}
n = next;
}
- return rel;
}
if (is_select(rel->op) && r && r->op == op_project && !(rel_is_ref(r))){
sql_rel *pl = r->l;
/* we cannot push through rank (row_number etc) functions or
projects with distinct */
- if (!pl || project_unsafe(r,1))
- return rel;
-
- /* introduce selects under the project (if needed) */
- set_processed(pl);
- for (n = exps->h; n;) {
- node *next = n->next;
- sql_exp *e = n->data, *ne = NULL;
-
- if (e->type == e_cmp) {
- ne = exp_push_down_prj(v->sql, e, r, pl);
-
- /* can we move it down */
- if (ne && ne != e && pl->exps) {
- if (!is_select(pl->op) ||
rel_is_ref(pl))
- r->l = pl =
rel_select(v->sql->sa, pl, NULL);
- rel_select_add_exp(v->sql->sa, pl, ne);
- list_remove_node(exps, NULL, n);
- v->changes++;
+ if (pl && !project_unsafe(r, 1)) {
+ /* introduce selects under the project (if needed) */
+ set_processed(pl);
+ for (n = exps->h; n;) {
+ node *next = n->next;
+ sql_exp *e = n->data, *ne = NULL;
+
+ if (e->type == e_cmp) {
+ ne = exp_push_down_prj(v->sql, e, r,
pl);
+
+ /* can we move it down */
+ if (ne && ne != e && pl->exps) {
+ if (!is_select(pl->op) ||
rel_is_ref(pl))
+ r->l = pl =
rel_select(v->sql->sa, pl, NULL);
+ rel_select_add_exp(v->sql->sa,
pl, ne);
+ list_remove_node(exps, NULL, n);
+ v->changes++;
+ }
}
- }
- n = next;
- }
- return rel;
- }
- return rel;
+ n = next;
+ }
+ }
+ }
+ return try_remove_empty_select(v, rel);
}
static sql_rel *
@@ -4699,6 +4698,8 @@ rel_push_select_down_join(visitor *v, sq
}
n = next;
}
+ if (is_join(rel->op) && list_empty(rel->exps))
+ rel->exps = NULL; /* crossproduct */
}
return rel;
}
@@ -5037,6 +5038,8 @@ rel_join_push_exps_down(visitor *v, sql_
r->exps = rexps;
}
}
+ if (is_join(rel->op) && list_empty(rel->exps))
+ rel->exps = NULL; /* crossproduct */
}
return rel;
}
@@ -5492,7 +5495,6 @@ rel_push_select_down_union(visitor *v, s
{
if (is_select(rel->op) && rel->l && rel->exps) {
sql_rel *u = rel->l, *ou = u;
- sql_rel *s = rel;
sql_rel *ul = u->l;
sql_rel *ur = u->r;
@@ -5528,11 +5530,12 @@ rel_push_select_down_union(visitor *v, s
/* introduce selects under the set (if needed) */
set_processed(ul);
set_processed(ur);
- ul = rel_select(v->sql->sa, ul, NULL);
- ur = rel_select(v->sql->sa, ur, NULL);
-
- ul->exps = exps_copy(v->sql, s->exps);
- ur->exps = exps_copy(v->sql, s->exps);
+ if (rel_is_ref(rel) || !list_empty(rel->exps)) { /* don't
generate empty selects */
+ ul = rel_select(v->sql->sa, ul, NULL);
+ ul->exps = exps_copy(v->sql, rel->exps);
+ ur = rel_select(v->sql->sa, ur, NULL);
+ ur->exps = exps_copy(v->sql, rel->exps);
+ }
rel = rel_inplace_setop(v->sql, rel, ul, ur, op_union,
rel_projections(v->sql, rel, NULL, 1, 1));
v->changes++;
@@ -9606,7 +9609,6 @@ optimize_rel(mvc *sql, sql_rel *rel, int
ev = { .sql = sql, .value_based_opt = value_based_opt,
.storage_based_opt = storage_based_opt };
global_props gp = (global_props) {.cnt = {0},};
rel_properties(sql, &gp, rel);
- int changes = 0;
TRC_DEBUG_IF(SQL_REWRITER) {
int i;
@@ -9691,12 +9693,8 @@ optimize_rel(mvc *sql, sql_rel *rel, int
if (gp.cnt[op_union]) {
rel = rel_visitor_bottomup(&v, rel,
&rel_remove_union_partitions);
- if (gp.cnt[op_select]) {
- changes = v.changes;
+ if (gp.cnt[op_select])
rel = rel_visitor_topdown(&v, rel,
&rel_push_select_down_union);
- if (v.changes > changes)
- rel = rel_visitor_bottomup(&ev, rel,
&rel_remove_empty_select);
- }
}
if (gp.cnt[op_groupby])
@@ -9724,11 +9722,8 @@ optimize_rel(mvc *sql, sql_rel *rel, int
if (gp.cnt[op_join])
rel = rel_visitor_topdown(&v, rel,
&rel_push_count_down);
if (level <= 0) {
- changes = v.changes;
if (gp.cnt[op_select])
rel = rel_visitor_topdown(&v, rel,
&rel_push_select_down);
- if (v.changes > changes)
- rel = rel_visitor_bottomup(&ev, rel,
&rel_remove_empty_select);
if (gp.cnt[op_join] || gp.cnt[op_semi] ||
gp.cnt[op_anti] || gp.cnt[op_left]) {
/* push_join_down introduces semijoins */
/* rewrite semijoin (A, join(A,B)) into
semijoin (A,B) */
@@ -9754,12 +9749,8 @@ optimize_rel(mvc *sql, sql_rel *rel, int
/* Important -> Make sure rel_push_select_down gets called after
rel_join_order,
because pushing down select expressions makes rel_join_order more
difficult */
- if (gp.cnt[op_select] && (gp.cnt[op_join] || gp.cnt[op_semi] ||
gp.cnt[op_anti] || gp.cnt[op_left] || gp.cnt[op_right])) {
- changes = v.changes;
+ if (gp.cnt[op_select] && (gp.cnt[op_join] || gp.cnt[op_semi] ||
gp.cnt[op_anti] || gp.cnt[op_left] || gp.cnt[op_right]))
rel = rel_visitor_topdown(&v, rel, &rel_push_select_down);
- if (v.changes > changes)
- rel = rel_visitor_bottomup(&ev, rel,
&rel_remove_empty_select);
- }
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])
rel = rel_visitor_topdown(&v, rel, &rel_simplify_fk_joins);
@@ -9777,12 +9768,8 @@ optimize_rel(mvc *sql, sql_rel *rel, int
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_func_down);
- if (gp.cnt[op_select]) {
- changes = v.changes;
+ if (gp.cnt[op_select])
rel = rel_visitor_topdown(&v, rel,
&rel_push_select_down);
- if (v.changes > changes)
- rel = rel_visitor_bottomup(&ev, rel,
&rel_remove_empty_select);
- }
}
if (gp.cnt[op_topn] || gp.cnt[op_sample])
diff --git a/sql/server/rel_rewriter.c b/sql/server/rel_rewriter.c
--- a/sql/server/rel_rewriter.c
+++ b/sql/server/rel_rewriter.c
@@ -208,24 +208,10 @@ rewrite_simplify(visitor *v, sql_rel *re
sql_rel *
rel_remove_empty_select(visitor *v, sql_rel *rel)
{
- if ((is_join(rel->op) || is_semi(rel->op) || is_select(rel->op) ||
is_project(rel->op) || is_topn(rel->op) || is_sample(rel->op)) && rel->l) {
- sql_rel *l = rel->l;
- if (is_select(l->op) && !(rel_is_ref(l)) &&
list_empty(l->exps)) {
- rel->l = l->l;
- l->l = NULL;
- rel_destroy(l);
- v->changes++;
- }
- }
- if ((is_join(rel->op) || is_semi(rel->op) || is_set(rel->op)) &&
rel->r) {
- sql_rel *r = rel->r;
- if (is_select(r->op) && !(rel_is_ref(r)) &&
list_empty(r->exps)) {
- rel->r = r->l;
- r->l = NULL;
- rel_destroy(r);
- v->changes++;
- }
- }
+ if ((is_join(rel->op) || is_semi(rel->op) || is_select(rel->op) ||
is_project(rel->op) || is_topn(rel->op) || is_sample(rel->op)) && rel->l)
+ rel->l = try_remove_empty_select(v, rel->l);
+ if ((is_join(rel->op) || is_semi(rel->op) || is_set(rel->op)) && rel->r)
+ rel->r = try_remove_empty_select(v, rel->r);
if (is_join(rel->op) && list_empty(rel->exps))
rel->exps = NULL; /* crossproduct */
return rel;
diff --git a/sql/server/rel_rewriter.h b/sql/server/rel_rewriter.h
--- a/sql/server/rel_rewriter.h
+++ b/sql/server/rel_rewriter.h
@@ -19,6 +19,20 @@
extern sql_exp *rewrite_simplify_exp(visitor *v, sql_rel *rel, sql_exp *e, int
depth);
extern sql_rel *rewrite_simplify(visitor *v, sql_rel *rel);
+
+static inline sql_rel *
+try_remove_empty_select(visitor *v, sql_rel *rel)
+{
+ if (is_select(rel->op) && !(rel_is_ref(rel)) && list_empty(rel->exps)) {
+ sql_rel *l = rel->l;
+ rel->l = NULL;
+ rel_destroy(rel);
+ v->changes++;
+ rel = l;
+ }
+ return rel;
+}
+
extern sql_rel *rel_remove_empty_select(visitor *v, sql_rel *rel);
extern sql_exp *exp_push_down(mvc *sql, sql_exp *e, sql_rel *f, sql_rel *t);
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