I'm working on an IRC bot, forked from a modular bot called Skybot.
There are two other modules that make use of the sqlite3 database by default; they have both been removed and their tables dropped, so I know that the issue is somewhere in what I'm doing.
I only call 3 db.execute() statements in the whole thing and they're all immediately committed. This thing isn't getting hammered with queries either, but the lock remains.
Relevant code:
def db_init(db):
db.execute("create table if not exists searches"
"(search_string UNIQUE PRIMARY KEY,link)")
db.commit()
return db
def get_link(db, inp):
row = db.execute("select link from searches where"
" search_string=lower(?) limit 1",
(inp.lower(),)).fetchone()
db.commit()
return row
def store_link(db, stub, search):
db.execute("insert into searches (search_string, link) VALUES (?, ?)", (search.lower(), stub))
db.commit()
return stub
If the script only has to touch db_init() and get_link() it breezes through, but if it needs to call store_link() while the database is unlocked it will do the insert, but doesn't seem to be committing it in a way that future calls to get_link() can read it until the bot restarts.
The bot's db.py:
import os
import sqlite3
def get_db_connection(conn, name=''):
"returns an sqlite3 connection to a persistent database"
if not name:
name = '%s.%s.db' % (conn.nick, conn.server)
filename = os.path.join(bot.persist_dir, name)
return sqlite3.connect(filename, isolation_level=None)
bot.get_db_connection = get_db_connection
I did adjust the isolation_level myself, that was originally timeout=10. I am fairly stumped.
EDIT: The usages of get_db_connection():
main.py (main loop):
def run(func, input):
args = func._args
if 'inp' not in input:
input.inp = input.paraml
if args:
if 'db' in args and 'db' not in input:
input.db = get_db_connection(input.conn)
if 'input' in args:
input.input = input
if 0 in args:
out = func(input.inp, **input)
else:
kw = dict((key, input[key]) for key in args if key in input)
out = func(input.inp, **kw)
else:
out = func(input.inp)
if out is not None:
input.reply(unicode(out))
...
def start(self):
uses_db = 'db' in self.func._args
db_conns = {}
while True:
input = self.input_queue.get()
if input == StopIteration:
break
if uses_db:
db = db_conns.get(input.conn)
if db is None:
db = bot.get_db_connection(input.conn)
db_conns[input.conn] = db
input.db = db
try:
run(self.func, input)
except:
traceback.print_exc()
Send conn in your functions, along with db, as mentioned. If you wrote the code yourself, you'll know where the database actually is. Conventionally you would do something like:
db = sqlite3.connect('database.db')
conn = db.cursor()
Then for general usage:
db.execute("...")
conn.commit()
Hence, in your case:
def db_init(conn,db):
db.execute("create table if not exists searches"
"(search_string UNIQUE PRIMARY KEY,link)")
conn.commit()
return db
def get_link(conn,db, inp):
row = db.execute("select link from searches where"
" search_string=lower(?) limit 1",
(inp.lower(),)).fetchone()
conn.commit()
return row
def store_link(conn,db, stub, search):
db.execute("insert into searches (search_string, link) VALUES (?, ?)", (search.lower(), stub))
conn.commit()
return stub
On the basis that you have set the isolation_level to automatic updates:
sqlite3.connect(filename, isolation_level=None)
There is no need whatsoever for the commit statements in your code
Edit:
Wrap your execute statements in try statements, so that you at least have a chance of finding out what is going on i.e.
import sqlite3
def get_db(name=""):
if not name:
name = "db1.db"
return sqlite3.connect(name, isolation_level=None)
connection = get_db()
cur = connection.cursor()
try:
cur.execute("create table if not exists searches"
"(search_string UNIQUE PRIMARY KEY,link)")
except sqlite3.Error as e:
print 'Searches create Error '+str(e)
try:
cur.execute("insert into searches (search_string, link) VALUES (?, ?)", ("my search", "other"))
except sqlite3.Error as e:
print 'Searches insert Error '+str(e)
cur.execute("select link from searches where search_string=? limit 1", ["my search"])
s_data = cur.fetchone()
print 'Result:', s_data
Related
We need to do bulk updates of many rows in our Postgres DB, and want to use the SQL syntax below. How do we do that using psycopg2?
UPDATE table_to_be_updated
SET msg = update_payload.msg
FROM (VALUES %(update_payload)s) AS update_payload(id, msg)
WHERE table_to_be_updated.id = update_payload.id
RETURNING *
Attempt 1 - Passing values
We need to pass a nested iterable format to the psycopg2 query. For the update_payload, I've tried passing a list of lists, list of tuples, and tuples of tuples. It all fails with various errors.
Attempt 2 - Writing custom class with __conform__
I've tried to write a custom class that we can use for these operations, which would return
(VALUES (row1_col1, row1_col2), (row2_col1, row2_col2), (...))
I've coded up like this following instructions here, but it's clear that I'm doing something wrong. For instance, in this approach I'll have to handle quoting of all values inside the table, which would be cumbersome and prone to errors.
class ValuesTable(list):
def __init__(self, *args, **kwargs):
super(ValuesTable, self).__init__(*args, **kwargs)
def __repr__(self):
data_in_sql = ""
for row in self:
str_values = ", ".join([str(value) for value in row])
data_in_sql += "({})".format(str_values)
return "(VALUES {})".format(data_in_sql)
def __conform__(self, proto):
return self.__repr__()
def getquoted(self):
return self.__repr__()
def __str__(self):
return self.__repr__()
EDIT: If doing a bulk update can be done in a faster/cleaner way using another syntax than the one in my original question, then I'm all ears!
Requirements:
Postgres table, consisting of the fields id and msg (and potentially other fields)
Python data containing new values for msg
Postgres table should be updated via psycopg2
Example Table
CREATE TABLE einstein(
id CHAR(5) PRIMARY KEY,
msg VARCHAR(1024) NOT NULL
);
Test data
INSERT INTO einstein VALUES ('a', 'empty');
INSERT INTO einstein VALUES ('b', 'empty');
INSERT INTO einstein VALUES ('c', 'empty');
Python Program
Hypothetical, self-contained example program with quotations of a famous physicist.
import sys
import psycopg2
from psycopg2.extras import execute_values
def print_table(con):
cur = con.cursor()
cur.execute("SELECT * FROM einstein")
rows = cur.fetchall()
for row in rows:
print(f"{row[0]} {row[1]}")
def update(con, einstein_quotes):
cur = con.cursor()
execute_values(cur, """UPDATE einstein
SET msg = update_payload.msg
FROM (VALUES %s) AS update_payload (id, msg)
WHERE einstein.id = update_payload.id""", einstein_quotes)
con.commit()
def main():
con = None
einstein_quotes = [("a", "Few are those who see with their own eyes and feel with their own hearts."),
("b", "I have no special talent. I am only passionately curious."),
("c", "Life is like riding a bicycle. To keep your balance you must keep moving.")]
try:
con = psycopg2.connect("dbname='stephan' user='stephan' host='localhost' password=''")
print_table(con)
update(con, einstein_quotes)
print("rows updated:")
print_table(con)
except psycopg2.DatabaseError as e:
print(f'Error {e}')
sys.exit(1)
finally:
if con:
con.close()
if __name__ == '__main__':
main()
Prepared Statements Alternative
import sys
import psycopg2
from psycopg2.extras import execute_batch
def print_table(con):
cur = con.cursor()
cur.execute("SELECT * FROM einstein")
rows = cur.fetchall()
for row in rows:
print(f"{row[0]} {row[1]}")
def update(con, einstein_quotes, page_size):
cur = con.cursor()
cur.execute("PREPARE updateStmt AS UPDATE einstein SET msg=$1 WHERE id=$2")
execute_batch(cur, "EXECUTE updateStmt (%(msg)s, %(id)s)", einstein_quotes, page_size=page_size)
cur.execute("DEALLOCATE updateStmt")
con.commit()
def main():
con = None
einstein_quotes = ({"id": "a", "msg": "Few are those who see with their own eyes and feel with their own hearts."},
{"id": "b", "msg": "I have no special talent. I am only passionately curious."},
{"id": "c", "msg": "Life is like riding a bicycle. To keep your balance you must keep moving."})
try:
con = psycopg2.connect("dbname='stephan' user='stephan' host='localhost' password=''")
print_table(con)
update(con, einstein_quotes, 100) #choose some meaningful page_size here
print("rows updated:")
print_table(con)
except psycopg2.DatabaseError as e:
print(f'Error {e}')
sys.exit(1)
finally:
if con:
con.close()
if __name__ == '__main__':
main()
Output
The above program would output the following to the debug console:
a empty
b empty
c empty
rows updated:
a Few are those who see with their own eyes and feel with their own hearts.
b I have no special talent. I am only passionately curious.
c Life is like riding a bicycle. To keep your balance you must keep moving.
Short answer! Use execute_values(curs, sql, args), see docs
For those looking for short straightforward answer. Sample code to update users in bulk;
from psycopg2.extras import execute_values
sql = """
update users u
set
name = t.name,
phone_number = t.phone_number
from (values %s) as t(id, name, phone_number)
where u.id = t.id;
"""
rows_to_update = [
(2, "New name 1", '+923002954332'),
(5, "New name 2", '+923002954332'),
]
curs = conn.cursor() # Assuming you already got the connection object
execute_values(curs, sql, rows_to_update)
If you're using the uuid for primary key, and haven't registered the uuid data type in psycopg2 (keeping uuid as a python string), you can always use this condition u.id = t.id::uuid.
I have a problem with creating SQL query for Oracle database using Python.
I want to bind string variable and it does not work, could you tell me what am I doing wrong?
This is my code:
import cx_Oracle
dokList = []
def LoadDatabase():
conn = None
cursor = None
try:
conn = cx_Oracle.connect("login", "password", "localhost")
cursor = conn.cursor()
query = "SELECT * FROM DOCUMENT WHERE DOC = :param"
for doknumber in dokList:
cursor.execute(query, {'doknr':doknumber})
print(cursor.rowcount)
except cx_Oracle.DatabaseError as err:
print(err)
finally:
if cursor:
cursor.close()
if conn:
conn.close()
def CheckData():
with open('changedNamed.txt') as f:
lines = f.readlines()
for line in lines:
dokList.append(line)
CheckData()
LoadDatabase()
The output of cursor.rowcount is 0 but it should be number greater than 0.
You're using a dictionary ({'doknr' : doknumber}) for your parameter, so it's a named parameter - the :param needs to match the key name. Try this:
query = "SELECT * FROM DOCUMENT WHERE DOC = :doknr"
for doknumber in dokList:
cursor.execute(query, {'doknr':doknumber})
print(cursor.rowcount)
For future troubleshooting, to check whether your parameter is getting passed properly, you can also try changing your query to "select :param from dual".
I'm learning python since last few weeks. For better learning, I decided to work on some project. So here is my Class for MySQL connection and demo example as well. Can you please tell me. What other improvement can be possible for following code?
Structure?
What else I can do to optimize code?
And Please forgive. If I'm doing some silly mistakes in code. (I'm learning)
#!/usr/bin/python
import pymysql
# select (table, parameter)
# insert (table, data)
# update (table, id, data)
# delete (table, id)
class MySQL:
def __init__(self):
self.sort_by = ""
self.order = ""
# initiate database connection.
self.connection = pymysql.connect(host='localhost',
user='root',
password='',
db='sherlock',
charset='utf8mb4')
self.cursor = self.connection.cursor(pymysql.cursors.DictCursor)
# this function is for selecting any feild on any table.(feilds veriable is optinal)
def select(self, table, *feilds):
flds = "" #differnt name for feilds veriable.
if not feilds:
flds = '*'
else:
for f in feilds:
if not flds:
flds = f
else:
flds += ",`%s`" % f
sql = "SELECT %s FROM `%s` " % (flds, table)
if self.sort_by:
sql = sql +"order by "+ str(self.sort_by) +" "+ str(self.order)
print sql
self.cursor.execute(sql)
result = self.cursor.fetchall()
return result
# This function is for data sorting for Mysql; but optinal.
# example : SELECT * FROM `users` order by id asc
def order_by(self, sort_by="", order="", *args, **kwargs):
self.sort_by = sort_by
self.order = order
# this function is for closing Mysql connection
def close(self):
self.connection.close()
########### END OF MySQL CLASS #############
sql = MySQL()
# sql.order_by function should be called before the sql.select() function.
sql.order_by("email")
# this will select all the feilds from `users` table.
# you can specify whichever feilds you want to return. like : sql.select("users", "id, email")
result = sql.select("users", "password")
for email in result:
print email["password"]
sql.close()
I have a small problem with this class which handle my DB. It still saying:
cursor.execute(sql)
ValueError: operation parameter must be str
I tried lots of things but nothing work as i want. I looked over https://docs.python.org/3.4/library/sqlite3.html and i'm sure i do the same things.
import sqlite3
class Database():
def __init__(self):
try:
self.db = sqlite3.connect('../database.sqlite')
self.cur = self.db.cursor()
self.cur.execute('pragma foreign_keys="1"')
except sqlite3.Error as e:
raise e
def select(self,sql):
cursor = self.db.cursor()
cursor.execute(sql)
records = cursor.fetchall()
cursor.close()
return records
def insert(self,sql):
cursor = self.db.cursor()
cursor.execute(sql)
newID = cursor.lastrowid
self.db.commit()
cursor.close()
return newID
def execute(self,sql):
""" execute any SQL statement but no return value given """
cursor = self.db.cursor()
cursor.execute(sql)
self.db.commit()
cursor.close()
if __name__ == '__main__':
db = Database()
#sql = "SELECT skuref, titre_prod FROM product"
t = ("888888",)
sql= "UPDATE product SET created = 1 WHERE skuref = ?", t
db.execute(sql)
If someone can help me it would be grateful.Later i wanted to pass something like this in the main program inside a for loop
lastpost = record[0]
if created = True
sql = "UPDATE product SET created = 1 WHERE skuref = ?",(lastpost,)
db.execute(sql)
sql is a tuple containing SQL statement and the parameters.
Change as following, so that sql and parameters are passed separately, instead of being passed as a tuple:
def execute(self, sql):
""" execute any SQL statement but no return value given """
cursor = self.db.cursor()
cursor.execute(*sql) # <------
self.db.commit()
cursor.close()
With your statement
sql = "UPDATE product SET created = 1 WHERE skuref = ?",(lastpost,)
you have created a tupel like
("UPDATE product SET created = 1 WHERE skuref = ?", (lastpost,))
You have to give the arguments as parameters to the execute() function.
Also your if statement is bad: no :, = instead of == and the whole check for True is no nesesary.
Try this:
lastpost = record[0]
if created:
sql = "UPDATE product SET created = 1 WHERE skuref = ?"
db.execute(sql, lastpost)
Issue: I can't figure out how to run a query in the correct way so that it returns a mapped dictionary. The query will use counts from multiple tables.
I am using psycopg2 for a postgresql database, and I will be using the results to create a report on day to day deltas on these counts.
Given that, can someone provide an example on how to execute multiple queries and return a dictionary that I can use for comparison purposes? Thanks! I image in a for loop is needed somewhere in here.
tables = ['table1', 'table2']
def db_query():
query = "select count(*) from (a_table) where error_string != '';"
conn = psycopg2.connect(database=db, user=user, password=password, host=host)
cur = conn.cursor(cursor_factory=psycopg2.extras.DictCursor)
cur.execute(query, tables)
output = cur.fetchall()
conn.close()
return output
I haven't used postgresql, so you might want to also check this out as a reference: How to store count values in python.
That being said, rearrange your code into something like this. Be sure to make conn global so you don't have to make more than one connection, and make sure you're also closing cur:
conn = None
def driverFunc():
global conn
try:
conn = psycopg2.connect(database=db, user=user, password=password, host=host)
tables = ['table1', 'table2']
countDict = {}
for thisTable in tables:
db_query(thisTable, countDict)
finally:
if not conn == None:
conn.close()
def db_query(tableName, countDict):
# Beware of SQL injection with the following line:
query = "select count(*) from " + tableName + " where error_string != '';"
cur = None
try:
cur = conn.cursor(cursor_factory=psycopg2.extras.DictCursor)
cur.execute(query)
countDict[tableName] = int(cur.fetchone())
finally:
if not cur == None:
cur.close()