MonetDB: Jun2020 - Don't run rewrite_ifthenelse again for the sa...

[Pedro Ferreira]

Changeset: d788347f7b7b for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=d788347f7b7b
Modified Files:
        sql/server/rel_unnest.c
Branch: Jun2020
Log Message:

Don't run rewrite_ifthenelse again for the same expression once the isnull 
condition has been added


diffs (48 lines):

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
@@ -2616,7 +2616,7 @@ rewrite_ifthenelse(mvc *sql, sql_rel *re
                                set_single(usq);
                        e = exp_rel(sql, usq);
                } else
-               if ((has_nil(cond) || (inner && is_outerjoin(inner->op))) && 
(cond->type != e_func || !is_isnull_func(nf))) {
+               if (!e->used && (has_nil(cond) || (inner && 
is_outerjoin(inner->op))) && (cond->type != e_func || !is_isnull_func(nf))) {
                        /* add is null */
                        sql_exp *condnil = rel_unop_(sql, rel, cond, NULL, 
"isnull", card_value);
 
@@ -2624,6 +2624,7 @@ rewrite_ifthenelse(mvc *sql, sql_rel *re
                        cond = exp_copy(sql, cond);
                        cond = rel_nop_(sql, rel, condnil, 
exp_atom_bool(sql->sa, 0), cond, NULL, NULL, "ifthenelse", card_value);
                        l->h->data = cond;
+                       e->used = 1;
                }
        }
        return e;
@@ -2995,6 +2996,18 @@ rewrite_values(mvc *sql, sql_rel *rel, i
        return rel;
 }
 
+static sql_exp *
+reset_exp_used(mvc *sql, sql_rel *rel, sql_exp *e, int depth, int *changes)
+{
+       (void) sql;
+       (void) rel;
+       (void) depth;
+       (void) changes;
+
+       e->used = 0;
+       return e;
+}
+
 sql_rel *
 rel_unnest(mvc *sql, sql_rel *rel)
 {
@@ -3016,6 +3029,8 @@ rel_unnest(mvc *sql, sql_rel *rel)
        rel = rel_exp_visitor_bottomup(sql, rel, &rewrite_complex, &changes);
 
        rel = rel_exp_visitor_bottomup(sql, rel, &rewrite_ifthenelse, 
&changes);        /* add isnull handling */
+       rel = rel_exp_visitor_bottomup(sql, rel, &reset_exp_used, &changes);    
/* reset used flag from ifthenelse re-writer, so it can be used again by the 
rel_dce optimizer */
+
        rel = rel_visitor_bottomup(sql, rel, &rewrite_values, &changes);
        rel = rel_exp_visitor_bottomup(sql, rel, &rewrite_exp_rel, &changes);
        rel = rel_visitor_bottomup(sql, rel, &rewrite_join2semi, &changes);     
/* where possible convert anyequal functions into marks */
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