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