#coding:utf-8

"""
ID:          issue-7092
ISSUE:       https://github.com/FirebirdSQL/firebird/issues/7092
TITLE:       Improve performance of CURRENT_TIME
DESCRIPTION:
    Test uses two procedures:
        * one with loop for integer values that does nothing more, and
        * second with same loop but with assigning from ticket: 'd = current_time' (on every iteration).

    Duration is measured as difference between psutil.Process(fb_pid).cpu_times() counters.
    We do these measures <N_MEASURES> times for each SP, and each result is added to the list
    which, in turn, is the source for median evaluation.
    Finally, we get ratio between minimal and maximal medians (see 'median_ratio')
    This ratio is about:
        * Windows: 0.6 ... 0.7
        * Linux: 0.5 ... 0.6
    Before fix it was more than 10.
    
    Test is considered as passed if median_ratio less than threshold <MAX_RATIO>.
NOTES:
    Number of iterations for loops differ: we have to perform 'sp_empty_loop' at least 1E6 times
    in order to get valuable difference between CPU user time counters and use it as denomitator.
    Procedure 'sp_ctime_loop' must be called for 10x times LESS than 'sp_empty_loop'.

    Confirmed problem on:
        5.0.0.362, 4.0.1.2699 (bith snapshots have date 01-jan-2022)
    Checked on 6.0.0.195, 5.0.0.1305, 4.0.5.3049.
"""

import psutil
import pytest
from firebird.qa import *

#--------------------------------------------------------------------
def median(lst):
    n = len(lst)
    s = sorted(lst)
    return (sum(s[n//2-1:n//2+1])/2.0, s[n//2])[n % 2] if n else None
#--------------------------------------------------------------------

###########################
###   S E T T I N G S   ###
###########################

# How many times we call procedures:
N_MEASURES = 15

# How many iterations must be done:
N_COUNT_TIME_LOOP = 100000
N_COUNT_EMPTY_LOOP = 1000000

# Maximal value for ratio between maximal and minimal medians
#
MAX_RATIO = 1.5
###############

init_script = \
f'''
    set term ^;
    create procedure sp_ctime_loop(a_limit int)
    as
        declare d time;
        declare n int = 1;
    begin
        while (n < a_limit) do
        begin
            d = current_time;
            n = n + 1;
        end
    end
    ^
    create procedure sp_empty_loop(a_limit int)
    as
        declare n int = 1;
    begin
        while (n < a_limit) do
        begin
            n = n + 1;
        end
    end
    ^
    commit
    ^
'''

db = db_factory(init = init_script, charset = 'win1251')
act = python_act('db')

expected_stdout = """
    Medians ratio: acceptable
"""

@pytest.mark.version('>=4.0.2')
def test_1(act: Action, capsys):
    
    with act.db.connect() as con:
        cur=con.cursor()
        cur.execute('select mon$server_pid as p from mon$attachments where mon$attachment_id = current_connection')
        fb_pid = int(cur.fetchone()[0])

        sp_time = {}
        for i in range(0, N_MEASURES):
            for sp_name in ('sp_ctime_loop', 'sp_empty_loop'):
                n_count = N_COUNT_TIME_LOOP if sp_name == 'sp_ctime_loop' else N_COUNT_EMPTY_LOOP
                fb_info_init = psutil.Process(fb_pid).cpu_times()
                cur.callproc( sp_name, (n_count,) )
                fb_info_curr = psutil.Process(fb_pid).cpu_times()
                sp_time[ sp_name, i ]  = max(fb_info_curr.user - fb_info_init.user, 0.000001)


    sp_ctime_median = median([v for k,v in sp_time.items() if k[0] == 'sp_ctime_loop'])
    sp_dummy_median = median([v for k,v in sp_time.items() if k[0] == 'sp_empty_loop'])
    #----------------------------------
    median_ratio = sp_ctime_median / sp_dummy_median

    print( 'Medians ratio: ' + ('acceptable' if median_ratio <= MAX_RATIO else '/* perf_issue_tag */ POOR: %s, more than threshold: %s' % ( '{:9g}'.format(median_ratio), '{:9g}'.format(MAX_RATIO) ) ) )
    if median_ratio > MAX_RATIO:
        print(f'CPU times for each of {N_MEASURES} measures:')
        for k,v in sp_time.items():
            print(k,':::',v)
        print(f'Median cpu time for {N_MEASURES} measures:')
        print('sp_ctime_median:',sp_ctime_median)
        print('sp_dummy_median:',sp_dummy_median)
        print('median_ratio:',median_ratio)

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