Lambda (Python 3.6) PyMySql Query EXISTS query always returns 1 - mysql

Question

I am trying to get a PyMySQL query in Lambda (Python 3.6) to return whether a user exists or not. I pass my slack user ID into the query. This is what I want to check in MySQL. I can run the same query through MySQL and it returns a 0, but for some reason, every time I call this query through lambda, it tells me the user exists (My database is empty). My query is function is this:
def userExists(user):
statement = f"SELECT EXISTS(SELECT 1 FROM slackDB.Assets WHERE userID LIKE '%{user}%')Assets"
tempBool = cursor.execute(statement, args=None)
conn.commit()
return tempBool
Here is the full code I am working with:
################################
# Slack Lambda handler.
################################
import sys
import logging
import os
import pymysql
import urllib
# Grab data from the environment.
BOT_TOKEN = os.environ["BOT_TOKEN"]
ASSET_TABLE = os.environ["ASSET_TABLE"]
REGION_NAME = os.getenv('REGION_NAME', 'us-east-2')
DB_NAME = "admin"
DB_PASSWORD = "somepassword"
DB_DATABASE = "someDB"
RDS_HOST = "myslackdb.somepseudourl.us-east-2.rds.amazonaws.com"
port = 3306
logger = logging.getLogger()
logger.setLevel(logging.INFO)
try:
conn = pymysql.connect(RDS_HOST, user=DB_NAME, passwd=DB_PASSWORD, db=DB_DATABASE, connect_timeout=5)
cursor = conn.cursor()
except:
logger.error("ERROR: Unexpected error: Could not connect to MySql instance.")
sys.exit()
# Define the URL of the targeted Slack API resource.
SLACK_URL = "https://slack.com/api/chat.postMessage"
def userExists(user):
statement = f"SELECT EXISTS(SELECT 1 FROM slackDB.Assets WHERE userID LIKE '%{user}%')Assets"
tempBool = cursor.execute(statement, args=None)
conn.commit()
return tempBool
def addUser(user):
statement = f"INSERT INTO `slackDB`.`Assets` (`userID`, `money`) VALUES ('{user}', '1000')"
tempBool = cursor.execute(statement, args=None)
conn.commit()
return tempBool
def lambda_handler(data, context):
# Slack challenge answer.
if "challenge" in data:
return data["challenge"]
# Grab the Slack channel data.
slack_event = data['event']
slack_userID = slack_event["user"]
slack_text = slack_event["text"]
channel_id = slack_event["channel"]
slack_reply = ""
# Ignore bot messages.
if "bot_id" in slack_event:
slack_reply = ""
else:
# Start data sift.
if slack_text.startswith("!networth"):
slack_reply = "Your networth is: "
elif slack_text.startswith("!price"):
command,asset = text.split()
slack_reply = f"The price of a(n) {asset} is: "
elif slack_text.startswith("!addme"):
if userExists(slack_userID):
slack_reply = f"User {slack_userID} already exists"
else:
slack_reply = f"Adding user {slack_userID}"
addUser(slack_userID)
# We need to send back three pieces of information:
data = urllib.parse.urlencode(
(
("token", BOT_TOKEN),
("channel", channel_id),
("text", slack_reply)
)
)
data = data.encode("ascii")
# Construct the HTTP request that will be sent to the Slack API.
request = urllib.request.Request(
SLACK_URL,
data=data,
method="POST"
)
# Add a header mentioning that the text is URL-encoded.
request.add_header(
"Content-Type",
"application/x-www-form-urlencoded"
)
# Fire off the request!
urllib.request.urlopen(request).read()
# Everything went fine.
return "200 OK"
I am typing '!addme' in slack and it always tells me the user exists. I have printed out my query statement and it is inputting my slack ID correctly. I have checked my table, and it is completely empty. I have run the query in MySQL and it returns a 0.
Does anyone have any ideas? Am I just derping this up on something easy? Any helps or hints is much appreciated.
Thanks,

Answer 1

I don't see a fetch from the cursor. Just the execute.
And the return from execute is the number of rows affected. For DML operations (INSERT/UPDATE/DELETE) that makes sense. But I wouldn't rely on the rows affected count for a SELECT.
In this case, the SELECT EXISTS query is going to either return a row, or throw an error. But the fact that the query returns a row doesn't tell us anything about the value of the Assets column.
From the query, it looks like we want to fetch a row, and then determine if the Assets column contains a 0 or 1 (or NULL).
After the query execution, try cur.fetchone to retrieve the row.
We could also execute a simpler query, and then use a fetch to determine if a row is returned or not.