Added/Updated tests\bugs\gh_6992_test.py: initial implementation. Additional tests will be added further.

tests/bugs/gh_6992_test.py

@@ -0,0 +1,141 @@
+#coding:utf-8
+
+"""
+ID:          issue-6992
+ISSUE:       6992
+TITLE:       Transform OUTER joins into INNER ones if the WHERE condition violates the outer join rules
+NOTES:
+    [17.02.2023] pzotov
+    Initial implementation. Additional tests will be added further.
+"""
+
+import pytest
+from firebird.qa import *
+
+db = db_factory()
+
+test_script = """
+    set bail on;
+    recreate table tmain(
+        id int primary key using index tmain_pk
+    );
+
+    recreate table tdetl_a(
+        id int primary key using index tdetl_a_pk
+        ,pid int
+        ,constraint tdetl_a_fk foreign key(pid) references tmain(id) using index tdetl_a_fk
+    );
+
+    recreate table tdetl_b(
+        id int primary key using index tdetl_b_pk
+        ,pid int NOT NULL
+        ,constraint tdetl_b_fk foreign key(pid) references tmain(id) using index tdetl_b_fk
+    );
+
+
+    insert into tmain(id)
+    select row_number()over() as i
+    from rdb$types
+    rows 20
+    ;
+
+    insert into tdetl_a(id, pid)
+    select i, iif(mod(i,3)=0, null, 1 + mod(i,20))
+    from (
+        select row_number()over() as i
+        from rdb$types, rdb$types
+        rows 10000
+    );
+    insert into tdetl_b select id,coalesce(pid,1) from tdetl_a;
+    commit;
+
+    set statistics index tmain_pk;
+    set statistics index tdetl_a_fk;
+    set statistics index tdetl_b_fk;
+
+    set planonly;
+    set explain on;
+
+    -- This must NOT be transformed because we make here ANTI-JOIN.
+    -- Outer join is the only way to get proper result here:
+    select *
+    from tmain m1
+    left join tdetl_a d1 on m1.id = d1.pid
+    where d1.pid is null
+    ;
+
+    -- This MUST be transformed to INNER join because WHERE expression effectively will skip nulls.
+    -- See also issue in the ticket:
+    -- "regular comparisons that ignore NULLs by their nature, will cause the LEFT->INNER transformation"
+    select *
+    from tmain m2
+    left join tdetl_a d2 on m2.id = d2.pid
+    where d2.pid  = 0
+    ;
+
+    -- This must NOT be transformed, see ticket:
+    -- "checks for NULL, e.g. WHERE T2.ID IS NOT NULL ..., would not transform LEFT into INNER"
+    select *
+    from tmain m3
+    left join tdetl_a d3 on m3.id = d3.pid
+    where d3.pid is not null
+    ;
+
+    -- This must NOT be transformed, reason is the same:
+    -- "checks for NULL, e.g. WHERE T2.ID IS NOT NULL ..., would not transform LEFT into INNER"
+    -- NB: the fact that column tdetl_b.pid is declared as NOT NULL is ignored here.
+    -- This limitation seems redunant here.
+    select *
+    from tmain m4
+    left join tdetl_b d4 on m4.id = d4.pid
+    where d4.pid is not null
+    ;
+"""
+
+act = isql_act('db', test_script)
+
+expected_stdout = """
+    Select Expression
+        -> Filter
+            -> Nested Loop Join (outer)
+                -> Table "TMAIN" as "M1" Full Scan
+                -> Filter
+                    -> Table "TDETL_A" as "D1" Access By ID
+                        -> Bitmap
+                            -> Index "TDETL_A_FK" Range Scan (full match)
+
+    Select Expression
+        -> Nested Loop Join (inner)
+            -> Filter
+                -> Table "TMAIN" as "M2" Access By ID
+                    -> Bitmap
+                        -> Index "TMAIN_PK" Unique Scan
+            -> Filter
+                -> Table "TDETL_A" as "D2" Access By ID
+                    -> Bitmap
+                        -> Index "TDETL_A_FK" Range Scan (full match)
+
+    Select Expression
+        -> Filter
+            -> Nested Loop Join (outer)
+                -> Table "TMAIN" as "M3" Full Scan
+                -> Filter
+                    -> Table "TDETL_A" as "D3" Access By ID
+                        -> Bitmap
+                            -> Index "TDETL_A_FK" Range Scan (full match)
+
+    Select Expression
+        -> Filter
+            -> Nested Loop Join (outer)
+                -> Table "TMAIN" as "M4" Full Scan
+                -> Filter
+                    -> Table "TDETL_B" as "D4" Access By ID
+                        -> Bitmap
+                            -> Index "TDETL_B_FK" Range Scan (full match)
+"""
+
+@pytest.mark.version('>=5.0')
+def test_1(act: Action):
+    act.expected_stdout = expected_stdout
+    act.execute(combine_output = True)
+    assert act.clean_stdout == act.clean_expected_stdout