"""Inspect PostgreSQL command id."""

import sys

import psycopg2

def query_result(cursor, rel_name):

"""Execute sql query."""

cursor.execute('select xmin, xmax, cmin, cmax, * from {0}'.format(rel_name))

return cursor.fetchall()

def show_result(label, res):

print('========== begin {0} query====='.format(label))

print('xmin, xmax, cmin, cmax, *')

for row in res:

print(' '.join(map(str, row)))

print('========== end {0} query====='.format(label))

def get_new_connection(host, port, user, password):

"""Initialize a new connection."""

return psycopg2.connect(

host=host, port=port, user=user, password=password, dbname='postgres')

def create_test_relation(cursor, rel_name):

cursor.execute('create table if not exists {0}(id int)'.format(rel_name))

def main():

if len(sys.argv) < 5:

print('python postgresql_command_id.py host port user password')

return 0

host = sys.argv[1]

port = int(sys.argv[2])

user = sys.argv[3]

password = sys.argv[4]

rel_name = 's_test_command_id'

con = get_new_connection(host, port, user, password)

with con.cursor() as cursor:

create_test_relation(cursor, rel_name)

cursor = con.cursor()

cursor.execute('insert into {0} values(1)'.format(rel_name))

show_result('first cursor', query_result(cursor, rel_name))

mid_cursor = con.cursor()

mid_cursor.execute('select xmin, xmax, cmin, cmax, * from {0}'.format(rel_name))

show_result('first cursor', query_result(cursor, rel_name))

new_cursor = con.cursor()

new_cursor.execute('insert into {0} values(2)'.format(rel_name))

show_result('new cursor', query_result(new_cursor, rel_name))

show_result('mid cursor', mid_cursor.fetchall())

if __name__ == '__main__':

main()