Changeset: 2b4c47f279af for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=2b4c47f279af
Modified Files:
sql/server/rel_optimizer.c
Branch: Jun2020
Log Message:
one more performance issue fixed.
diffs (62 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
@@ -2616,6 +2616,50 @@ has_no_selectivity(mvc *sql, sql_rel *re
return rel;
}
+/*
+ * Remove a redundant join
+ *
+ * join (L, Distinct Project(join(L,P) [ p.key == l.lkey]) [p.key]) [ p.key ==
l.lkey]
+ * =>
+ * join(L, P) [p.key==l.lkey]
+ */
+static sql_rel *
+rel_remove_redundant_join(mvc *sql, sql_rel *rel, int *changes)
+{
+ (void)sql;
+ if (is_join(rel->op) || is_semi(rel->op)) {
+ sql_rel *l = rel->l, *r = rel->r, *b, *p = NULL, *j;
+
+ if (is_basetable(l->op) && is_simple_project(r->op) &&
need_distinct(r)) {
+ b = l;
+ p = r;
+ j = p->l;
+ } else if (is_basetable(r->op) && is_simple_project(l->op) &&
need_distinct(l)) {
+ b = r;
+ p = l;
+ j = p->l;
+ }
+ if (!p || !j || !is_join(j->op))
+ return rel;
+ /* j must have b->l (ie table) */
+ sql_rel *jl = j->l, *jr = j->r;
+ if ((is_basetable(jl->op) && jl->l == b->l) ||
+ (is_basetable(jr->op) && jr->l == b->l)) {
+ int left = 0;
+ if (is_basetable(jl->op) && jl->l == b->l)
+ left = 1;
+ if (exp_match_list(j->exps, rel->exps)) {
+ p->l = (left)?rel_dup(jr):rel_dup(jl);
+ rel_destroy(j);
+ set_nodistinct(p);
+ (*changes)++;
+ return rel;
+ }
+ }
+ }
+ return rel;
+}
+
static sql_column *
is_fk_column_of_pk(sql_rel *rel, sql_column *pkc, sql_exp *e) /* test if e is
a foreing key column for the pk on pkc */
{
@@ -9161,6 +9205,7 @@ optimize_rel(mvc *sql, sql_rel *rel, int
rel = rel_visitor_bottomup(sql, rel,
&rel_simplify_math, &changes);
rel = rel_visitor_bottomup(sql, rel,
&rel_distinct_aggregate_on_unique_values, &changes);
rel = rel_visitor_bottomup(sql, rel,
&rel_push_down_bounds, &changes);
+ rel = rel_visitor_bottomup(sql, rel,
&rel_remove_redundant_join, &changes);
rel = rel_visitor_bottomup(sql, rel,
&rel_distinct_project2groupby, &changes);
}
}
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