#coding:utf-8

"""
ID:          issue-8291
ISSUE:       https://github.com/FirebirdSQL/firebird/issues/8291
TITLE:       NULLs should be skipped during index navigation when there's no lower bound and matched conditions are known to ignore NULLs
DESCRIPTION:
    Test uses script from ticket. We compare number of indexed reads with threshold - see variable MAX_ALLOWED_IDX_READS.
    BEFORE fix value of indexed was 500002 (both on 5.x and 6.x), after fix it became 886 (using default page_size = 8k).
NOTES:
    [25.10.2024] pzotov
    Confirmed problem on 6.0.0.485, 5.0.2.1519.
    Checked on 6.0.0.502-d2f4cf6, 5.0.2.1542-ab50e20 (intermediate builds).
"""

import pytest
from firebird.qa import *

############################
MAX_ALLOWED_IDX_READS = 1000
############################

init_sql = """
    create table test (id int);

    set term ^;
    execute block as
        declare n int = 1000000;
        declare i int = 0;
    begin
        while (i < n) do
        begin
            insert into test(id) values( iif(mod(:i, 2) = 0, null, :i) );
            i = i + 1;
        end
    end^
    set term ;^
    commit;

    create index test_id on test(id);
    commit;
"""
db = db_factory(page_size = 8192, init = init_sql)

act = python_act('db')

#-----------------------------------------------------------

@pytest.mark.version('>=5.0.2')
def test_1(act: Action, capsys):
    msg_prefix = 'Number of indexed reads:'
    expected_txt = 'EXPECTED'
    idx_reads = {}
    with act.db.connect() as con:
        cur = con.cursor()
        cur.execute("select rdb$relation_id from rdb$relations where rdb$relation_name = 'TEST'")
        test_rel_id = cur.fetchone()[0]
        idx_reads[test_rel_id] = 0

        for x_table in con.info.get_table_access_stats():
            if x_table.table_id == test_rel_id:
                idx_reads[test_rel_id] = -x_table.indexed

        cur.execute('select count(*) from (select id from test where id < 3 order by id)')
        data = cur.fetchall()

        for x_table in con.info.get_table_access_stats():
            if x_table.table_id == test_rel_id:
                idx_reads[test_rel_id] += x_table.indexed
            
        # BEFORE fix value of indexed was 500002. After fix: 886
        if idx_reads[test_rel_id] < MAX_ALLOWED_IDX_READS:
            print(f'{msg_prefix} {expected_txt}')
        else:
            print(f'{msg_prefix} UNEXPECTED: {idx_reads[test_rel_id]} - greater than threshold = {MAX_ALLOWED_IDX_READS}.')

    act.expected_stdout = f"""
        {msg_prefix} {expected_txt}
    """

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