MonetDB: Jul2021 - Don't forget null values when rewriting ifthe...

[Pedro Ferreira]

Changeset: 331767e4c517 for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/331767e4c517
Modified Files:
        sql/server/rel_unnest.c
Branch: Jul2021
Log Message:

Don't forget null values when rewriting ifthenelse.

This fixes sqlancer14 query and now into more misalignment hunting.

However rewriting the else condition into an or may give issues with subqueries 
on the condition.


diffs (38 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
@@ -3187,6 +3187,7 @@ rewrite_ifthenelse(visitor *v, sql_rel *
                sql_exp *cond = l->h->data;
                sql_exp *then_exp = l->h->next->data;
                sql_exp *else_exp = l->h->next->next->data;
+               sql_exp *not_cond, *cond_is_null;
 
                if (exp_has_rel(then_exp) || exp_has_rel(else_exp)) {
                        bool single = false;
@@ -3197,7 +3198,7 @@ rewrite_ifthenelse(visitor *v, sql_rel *
                        //      )[cond]
                        //      select(
                        //              project [else]
-                       //      )[not(cond)]
+                       //      )[not(cond) or cond is null]
                        //) [ cols ]
                        sql_rel *lsq = NULL, *rsq = NULL, *usq = NULL;
 
@@ -3224,10 +3225,15 @@ rewrite_ifthenelse(visitor *v, sql_rel *
                        rsq = rel_project(v->sql->sa, rsq, 
append(sa_list(v->sql->sa), else_exp));
                        cond = exp_copy(v->sql, cond);
                        exp_set_freevar(v->sql, cond, rsq);
+                       not_cond = exp_compare(v->sql->sa, cond, 
exp_atom_bool(v->sql->sa, 0), cmp_equal);
+                       cond = exp_copy(v->sql, cond);
+                       cond_is_null = exp_compare(v->sql->sa, cond, 
exp_atom(v->sql->sa, atom_general(v->sql->sa, exp_subtype(cond), NULL)), 
cmp_equal);
+                       set_has_no_nil(cond_is_null);
+                       set_semantics(cond_is_null);
                        set_processed(rsq);
-                       rsq = rel_select(v->sql->sa, rsq, 
exp_compare(v->sql->sa, cond, exp_atom_bool(v->sql->sa, 0), cmp_equal));
+                       rsq = rel_select(v->sql->sa, rsq, exp_or(v->sql->sa, 
list_append(new_exp_list(v->sql->sa), not_cond), 
list_append(new_exp_list(v->sql->sa), cond_is_null), 0));
                        usq = rel_setop(v->sql->sa, lsq, rsq, op_union);
-                       rel_setop_set_exps(v->sql, 
usq,append(sa_list(v->sql->sa), exp_ref(v->sql, e)));
+                       rel_setop_set_exps(v->sql, usq, 
append(sa_list(v->sql->sa), exp_ref(v->sql, e)));
                        if (single)
                                set_single(usq);
                        set_processed(usq);
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