firebird-qa/tests/bugs/gh_7853_test.py

#coding:utf-8

"""
ID:          issue-7853
ISSUE:       7853
TITLE:       Do not consider non-deterministic expressions as invariants in pre-filters
DESCRIPTION:
    Change in FB 5.x was pushed 14.12.2023 20:06:
    https://github.com/FirebirdSQL/firebird/commit/f0b7429a1873ed9470838da61bdca0bce748652d
    Functions gen_id(), rand(), gen_uuid(), rdb$set_context and some other are not considered as deterministic anymore.
    It means that explained plans for queries which used these functions will change: now they must NOT contain 'Filter (preliminary)'.
    This behavior changed since snapshot 5.0.0.1304 (date: 16-dec-2023).
NOTES:
    [17.12.2023] pzotov
    1. Explained plans for queries where 'tmain' have aliases 'm0'  ... 'm4' have:
       * 'Filter (preliminary)' - for snapshots before this fix
       * 'Filter' (WITHOUT preliminary) - after fix
    2. Last commit in the push is "deterministic uncorrelated subqueries to be considered as invariants" - but there is NO DIFFERENCE
       between explained plans for 5.x snapshots that belongs to time points just _before_ and _after_ this push.
       This is because push of PR#7853 has several commits, and one of them did broke such functionality whereas next
       commit - WITHIN THIS PUSH (!) - did restore previous state (letter by dimitr, 17.12.2023 21:17).

    3. Actually, NON-correlated subqueries became considered as INVARIANT much earlier, since 5.0.0.890, 10-jan-2023
       ("Merge pull request #7441 from FirebirdSQL/v5-pretty-explained-plan", a6ce0ec1632ec037b41b9cbcad42fd3ce6a9ea5e).
       It seems that this old commit (of 10-jan-2023) caused lot of old issues to be considered now as fixed, for example 
       https://github.com/FirebirdSQL/firebird/issues/3394
       Query where 'tmain' table has alias 'm4' (and 'tdetl' table is involved - in contrary to all other queries) - is from this ticket.
       This query explained plan must have "Sub-query (invariant)" since build 5.0.0.890

    Checked on 5.0.0.1304
    ::: NB ::: Build 6.0.0.180 - FAILS because this PR still not pushed in master branch. Waiting for commit.
"""

import pytest
from firebird.qa import *


init_sql = """
    set bail on;
    recreate sequence g;
    recreate table tmain(id int primary key using index tmain_pk, f01 int);
    recreate table tdetl(id int primary key using index tdetl_pk, pid int references tmain(id) using index tdetl_fk, f01 int);

    insert into tmain(id, f01) select row_number()over(), rand()* 1000 from rdb$types rows 100;
    insert into tdetl(id, pid, f01) select row_number()over(), 1+rand() * 49, rand()* 1000 from rdb$types,rdb$types rows 1000;
    commit;
    set statistics index tmain_pk;
    set statistics index tdetl_fk;
    commit;
"""

db = db_factory(init = init_sql)

query_lst = (
     "select count(*) from tmain m0 where gen_id(g,0) = 0"
    ,"select count(*) from tmain m1 where rand() > 0.5"
    ,"select count(*) from tmain m2 where gen_uuid() is not null"
    ,"select count(*) from tmain m3 where coalesce( rdb$set_context('USER_TRANSACTION', 'ROWS_COUNTER',cast(coalesce(rdb$get_context('USER_TRANSACTION', 'ROWS_COUNTER'),'0') as int) + 1 ), 0) >= 0"
    ,"select count(*) from tmain m4 where m4.f01 > ( select avg(f01) from tdetl d )"
)

act = python_act('db')

expected_stdout = """
    Select Expression
    ####-> Aggregate
    ########-> Filter
    ############-> Table "TMAIN" as "M0" Full Scan

    Select Expression
    ####-> Aggregate
    ########-> Filter
    ############-> Table "TMAIN" as "M1" Full Scan

    Select Expression
    ####-> Aggregate
    ########-> Filter
    ############-> Table "TMAIN" as "M2" Full Scan

    Select Expression
    ####-> Aggregate
    ########-> Filter
    ############-> Table "TMAIN" as "M3" Full Scan

    Sub-query (invariant)
    ####-> Singularity Check
    ########-> Aggregate
    ############-> Table "TDETL" as "D" Full Scan
    Select Expression
    ####-> Aggregate
    ########-> Filter
    ############-> Table "TMAIN" as "M4" Full Scan
"""
#---------------------------------------------------------
def replace_leading(source, char="#"):
    stripped = source.lstrip()
    return char * (len(source) - len(stripped)) + stripped
#---------------------------------------------------------
@pytest.mark.version('>=5.0,<6')
def test_1(act: Action, capsys):
    with act.db.connect() as con:
        cur = con.cursor()
        for q in query_lst:
            with cur.prepare(q) as ps:
                print( '\n'.join([replace_leading(s) for s in ps.detailed_plan .split('\n')]) )

    act.expected_stdout = expected_stdout
    act.stdout = capsys.readouterr().out
    assert act.clean_stdout == act.clean_expected_stdout