From afdd829546b40dd18d391ec2af06f458017601c3 Mon Sep 17 00:00:00 2001
From: pavel-zotov <p519446@yandex.ru>
Date: Wed, 15 Jan 2025 10:50:19 +0300
Subject: [PATCH] Added/Updated tests\bugs\gh_8379_test.py: Only FB-6.x can be
 checked, see notes. Checked on 6.0.0.577 - all OK.

---
 tests/bugs/gh_8379_test.py | 128 +++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 tests/bugs/gh_8379_test.py

diff --git a/tests/bugs/gh_8379_test.py b/tests/bugs/gh_8379_test.py
new file mode 100644
index 00000000..a012b991
--- /dev/null
+++ b/tests/bugs/gh_8379_test.py
@@ -0,0 +1,128 @@
+#coding:utf-8
+
+"""
+ID:          issue-8379
+ISSUE:       https://github.com/FirebirdSQL/firebird/issues/8379
+TITLE:       Incorrect cardinality estimation for retrievals with multiple compound indices having common set of fields
+DESCRIPTION:
+    
+NOTES:
+    [15.01.2025] pzotov
+
+    1. This ticket can NOT be checked on FB 5.x: there are no differences neither in explained plans nor in trace statistics
+       for snapshots before and after fix. Only cardinality estimation can be checked but this feature avaliable only in FB-6
+       via rdb$sql.explain() package (see doc/sql.extensions/README.sql_package.md).
+    2. Cardinality change can be seen only for second example provided in the ticket
+       ("Test #2: three conditions, two of them are mapped ... the third one is not mapped to an index")
+       // see also letter from dimitr 14.01.2025 15:06
+
+    3. Query :
+           select
+               plan_line as p_line
+               ,cardinality
+               ,access_path
+           from rdb$sql.explain(q'#
+               select count(*) as cnt_1
+               from t
+               where f1 = 99 and f2 = 99 and f3 = 99
+           #')
+       - must return rows with *different* cardinality for plan lines with "Filter" and "Table ... Access By ID":
+           P_LINE    CARDINALITY        ACCESS_PATH                 |
+           1             <null>          Select expression          |
+           2           1                 -> Aggregate               |
+           3           1.78675004326506  -> Filter                  | <<< THIS VALUE MUST BE MUCH LESS THAN ONE FOR P_LINE = 4 ('card_afte')
+           4          17.8675004326506   -> Table ... Access By ID  | <<< THIS IS VALUE BEFORE 'FILTER' IS APPLIED ('card_befo')
+     Before fix this was not so: cardinality value in line with "Filter" was the same as in line for "Table ... Access By ID":
+     Thanks to dimitr for suggestions.
+
+     Confirmed bug on 6.0.0.576.
+     Checked on 6.0.0.577 - all OK.
+"""
+
+import pytest
+from firebird.qa import *
+
+#############
+N_ROWS = 5000
+OK_MSG = 'Cardinality estimation: EXPECTED.'
+#############
+
+init_script = f"""
+    recreate view v_check_card as select 1 x from rdb$database;
+    recreate table test (id int primary key, f1 int, f2 int, f3 int);
+
+    set term ^;
+    execute block as
+        declare n int = {N_ROWS};
+        declare i int  = 0;
+    begin
+        while (i < n) do
+        begin
+             insert into test(id, f1, f2, f3) values(:i, mod(:i, 100), mod(:i, 200), mod(:i, 300));
+             i = i + 1;
+        end
+    end
+    ^
+    set term ;^
+    commit;
+
+    create index it1 on test(f1, f2);
+    create index it2 on test(f1, f3);
+    commit;
+
+    recreate view v_check_card as
+    with
+    a as (
+        select
+            plan_line
+            ,record_source_id
+            ,parent_record_source_id
+            ,level
+            ,cardinality
+            ,record_length
+            ,key_length
+            ,access_path
+        from rdb$sql.explain(q'#
+            select count(*) as cnt_1
+            from test
+            where f1 = 99 and f2 = 99 and f3 = 99
+        #')
+    )
+    ,b as (
+        select
+             a.plan_line
+            ,a.cardinality as card_afte
+            ,lead(a.cardinality)over(order by a.plan_line) card_befo
+            ,a.access_path
+        from a
+    )
+    select
+        iif(  b.card_afte / nullif(b.card_befo,0) < 1
+             ,'{OK_MSG}'
+             ,'Cardinality estimation INCORRECT, HAS NOT REDUCED: '
+               || 'card_befo = ' || b.card_befo
+               || ', card_afte = ' || b.card_afte
+               || ', card_afte / card_befo = ' || (b.card_afte / nullif(b.card_befo,0))
+           ) as msg
+    from b
+    where b.access_path containing 'filter';
+"""
+
+db = db_factory(init=init_script)
+
+test_script = """
+    set heading off;
+    select * from v_check_card;
+"""
+
+act = isql_act('db', test_script)
+
+expected_stdout = f"""
+    {OK_MSG}
+"""
+
+@pytest.mark.version('>=6.0')
+def test_1(act: Action):
+    act.expected_stdout = expected_stdout
+    act.execute(combine_output = True)
+    assert act.clean_stdout == act.clean_expected_stdout