Develop Reference

FastAPI db query stuck. Kubernetes

I have one small app that use fastapi. The problem is when I deploy it to my server and trying to make a post request to route which contains some database operations, it just stuck and gives me 504 error. But on my local machine it working well.
Here is how my db connecting:
app.add_event_handler("startup", tasks.create_start_app_handler(app))
app.add_event_handler("shutdown", tasks.create_stop_app_handler(app))
I tried to revert db connection from startup application to creation of this connection with closing it in different route to test and its worked. Like:
#app.get("/")
async def create_item():
engine = create_engine(
DB_URL
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()
t = engine.execute('SELECT * FROM auth_user').fetchone()
engine.dispose()
return t
How it's depend on events? Versions of postgresql are different, but I don't think it's because of it.
Currently I have deployment with 2 pods running in it. When I use psql command I can connect normally. So it only stuck in application, not it pod.

If somebody finds same, I fixed it by updating pgpoll from 4.2.2 to latest.

Python Database connection for informix DB using sqlalchemy

I'm trying to connect to remote informix DB as follows using python3 sqlalchemy but it fails to connect
sqlalchemy.create_engine("informix://usr1:pwd1#XXX:23300/DB_NAME;SERVER=dsinfmx").connect()
I get the below ERROR while connecting.
sqlalchemy.exc.NoSuchModuleError: Can't load plugin: sqlalchemy.dialects:informix
Can someone please provide some help on this.. From Dbeaver, DB server is accessible.

I assume you are using Informix Python drivers. If not please install Informix Python driver i.e IfxPy. Details to install Informix Python drivers are at this link https://github.com/OpenInformix/IfxPy/blob/master/README.md
Try out below code.
from sqlalchemy import create_engine
from sqlalchemy.dialects import registry
from sqlalchemy.orm import sessionmaker
registry.register("informix", "IfxAlchemy.IfxPy", "IfxDialect_IfxPy")
registry.register("informix.IfxPy", "IfxAlchemy.IfxPy", "IfxDialect_IfxPy")
registry.register("informix.pyodbc", "IfxAlchemy.pyodbc", "IfxDialect_pyodbc")
from sqlalchemy import Table, Column, Integer
ConStr = 'informix://<username>:<password>#<machine name>:<port number>/<database name>;SERVER=<server name>'
engine = create_engine(ConStr)
connection = engine.connect()
connection.close()
print( "Done2" )

How to connect to a cluster in Amazon Redshift using SQLAlchemy?

In Amazon Redshift's Getting Started Guide, it's mentioned that you can utilize SQL client tools that are compatible with PostgreSQL to connect to your Amazon Redshift Cluster.
In the tutorial, they utilize SQL Workbench/J client, but I'd like to utilize python (in particular SQLAlchemy). I've found a related question, but the issue is that it does not go into the detail or the python script that connects to the Redshift Cluster.
I've been able to connect to the cluster via SQL Workbench/J, since I have the JDBC URL, as well as my username and password, but I'm not sure how to connect with SQLAlchemy.
Based on this documentation, I've tried the following:
from sqlalchemy import create_engine
engine = create_engine('jdbc:redshift://shippy.cx6x1vnxlk55.us-west-2.redshift.amazonaws.com:5439/shippy')
ERROR:
Could not parse rfc1738 URL from string 'jdbc:redshift://shippy.cx6x1vnxlk55.us-west-2.redshift.amazonaws.com:5439/shippy'

I don't think SQL Alchemy "natively" knows about Redshift. You need to change the JDBC "URL" string to use postgres.
jdbc:postgres://shippy.cx6x1vnxlk55.us-west-2.redshift.amazonaws.com:5439/shippy
Alternatively, you may want to try using sqlalchemy-redshift using the instructions they provide.

I was running into the exact same issue, and then I remembered to include my Redshift credentials:
eng = create_engine('postgresql://[LOGIN]:[PASSWORD]#shippy.cx6x1vnxlk55.us-west-2.redshift.amazonaws.com:5439/shippy')

sqlalchemy-redshift is works for me, but after few days of reserch
packages (python3.4):
SQLAlchemy==1.0.14 sqlalchemy-redshift==0.5.0 psycopg2==2.6.2
First of all, I checked, that my query is working workbench (http://www.sql-workbench.net), then I force it work in sqlalchemy (this https://stackoverflow.com/a/33438115/2837890 helps to know that auto_commit or session.commit() must be):
db_credentials = (
'redshift+psycopg2://{p[redshift_user]}:{p[redshift_password]}#{p[redshift_host]}:{p[redshift_port]}/{p[redshift_database]}'
.format(p=config['Amazon_Redshift_parameters']))
engine = create_engine(db_credentials, connect_args={'sslmode': 'prefer'})
connection = engine.connect()
result = connection.execute(text(
"COPY assets FROM 's3://xx/xx/hello.csv' WITH CREDENTIALS "
"'aws_access_key_id=xxx_id;aws_secret_access_key=xxx'"
" FORMAT csv DELIMITER ',' IGNOREHEADER 1 ENCODING UTF8;").execution_options(autocommit=True))
result = connection.execute("select * from assets;")
print(result, type(result))
print(result.rowcount)
connection.close()
And after that, I forced to work sqlalchemy_redshift CopyCommand perhaps bad way, looks little tricky:
import sqlalchemy as sa
tbl2 = sa.Table(TableAssets, sa.MetaData())
copy = dialect_rs.CopyCommand(
assets,
data_location='s3://xx/xx/hello.csv',
access_key_id=access_key_id,
secret_access_key=secret_access_key,
truncate_columns=True,
delimiter=',',
format='CSV',
ignore_header=1,
# empty_as_null=True,
# blanks_as_null=True,
)
print(str(copy.compile(dialect=RedshiftDialect(), compile_kwargs={'literal_binds': True})))
print(dir(copy))
connection = engine.connect()
connection.execute(copy.execution_options(autocommit=True))
connection.close()
We make just that I made with sqlalchemy, excute query, except comine query by CopyCommand. I have not see some profit :(.

The following works for me with Databricks on all kinds of SQLs
import sqlalchemy as SA
import psycopg2
host = 'your_host_url'
username = 'your_user'
password = 'your_passw'
port = 5439
url = "{d}+{driver}://{u}:{p}#{h}:{port}/{db}".\
format(d="redshift",
driver='psycopg2',
u=username,
p=password,
h=host,
port=port,
db=db)
engine = SA.create_engine(url)
cnn = engine.connect()
strSQL = "your_SQL ..."
try:
cnn.execute(strSQL)
except:
raise

import sqlalchemy as db
engine = db.create_engine('postgres://username:password#url:5439/db_name')
This worked for me

pyodbc autocommit does not appear to work with sybase and sqlalchemy

I am connecting to a sybase ASE 15 database from Python 3.4 using pyodbc and executing a stored procedure.
All works as expected if I use native pyodbc:
import pd
import pyodbc
con = pyodbc.connect('DSN=dsn_name;UID=username;PWD=password', autocommit=True)
df = pd.read_sql("exec p_procecure #GroupName='GROUP'", con)
[Driver is Adaptive Server Enterprise].
I have to have autocommit=True and if I do no I get the following error:
DatabaseError: Execution failed on sql 'exec ....': ('ZZZZZ', "[ZZZZZ]
[SAP][ASE ODBC Driver][Adaptive Server Enterprise]Stored procedure
'p_procedure' may be run only in unchained transaction mode. The 'SET
CHAINED OFF' command will cause the current session to use unchained
transaction mode.\n (7713) (SQLExecDirectW)")
I attempt to achieve the same using SQLAlchemy (1.0.9):
from sqlalchemy import create_engine, engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.sql import text
url = r'sybase+pyodbc://username:password#dsn'
engine = create_engine(url, echo=True)
sess = sessionmaker(bind=engine).Session()
df = pd.read_sql(text("exec p_procedure #GroupName='GROUP'"),conn.execution_options(autocommit=True))
The error message is the same despite the fact I have specified autocommit=True on the connection. (I have also tested this at the session level but should not be necessary and made no difference).
DBAPIError: (pyodbc.Error) ('ZZZZZ', "[ZZZZZ] [SAP][ASE ODBC
Driver][Adaptive Server Enterprise]....
Can you see anything wrong here?
As always, any help would be much appreciated.

Passing the autocommit=True argument as an item in the connect_args argument dictionary does work:
connect_args = {'autocommit': True}
create_engine(url, connect_args=connect_args)
connect_args – a dictionary of options which will be passed directly
to the DBAPI’s connect() method as additional keyword arguments.

I had some problems with autocommit option. The only thing that worked for me was to change this option to True after establishing connection.
ConnString = 'Driver=%SQL_DRIVER%;Server=%SQL_SERVER%;Uid=%SQL_LOGIN%;Pwd=%SQL_PASSWORD%;'
SQL_CONNECTION = pyodbc.connect(ConnString)
SQL_CONNECTION.autocommit = True

How do I connect to SQL Server via sqlalchemy using Windows Authentication?

sqlalchemy, a db connection module for Python, uses SQL Authentication (database-defined user accounts) by default. If you want to use your Windows (domain or local) credentials to authenticate to the SQL Server, the connection string must be changed.
By default, as defined by sqlalchemy, the connection string to connect to the SQL Server is as follows:
sqlalchemy.create_engine('mssql://*username*:*password*#*server_name*/*database_name*')
This, if used using your Windows credentials, would throw an error similar to this:
sqlalchemy.exc.DBAPIError: (Error) ('28000', "[28000] [Microsoft][ODBC SQL Server Driver][SQL Server]Login failed for us
er '***S\\username'. (18456) (SQLDriverConnect); [28000] [Microsoft][ODBC SQL Server Driver][SQL Server]Login failed for us
er '***S\\username'. (18456)") None None
In this error message, the code 18456 identifies the error message thrown by the SQL Server itself. This error signifies that the credentials are incorrect.

In order to use Windows Authentication with sqlalchemy and mssql, the following connection string is required:
ODBC Driver:
engine = sqlalchemy.create_engine('mssql://*server_name*/*database_name*?trusted_connection=yes')
SQL Express Instance:
engine = sqlalchemy.create_engine('mssql://*server_name*\\SQLEXPRESS/*database_name*?trusted_connection=yes')

If you're using a trusted connection/AD and not using username/password, or otherwise see the following:
SAWarning: No driver name specified; this is expected by PyODBC when using >DSN-less connections
"No driver name specified; "
Then this method should work:
from sqlalchemy import create_engine
server = <your_server_name>
database = <your_database_name>
engine = create_engine('mssql+pyodbc://' + server + '/' + database + '?trusted_connection=yes&driver=ODBC+Driver+13+for+SQL+Server')

A more recent response if you want to connect to the MSSQL DB from a different user than the one you're logged with on Windows. It works as well if you are connecting from a Linux machine with FreeTDS installed.
The following worked for me from both Windows 10 and Ubuntu 18.04 using Python 3.6 & 3.7:
import getpass
from sqlalchemy import create_engine
password = getpass.getpass()
eng_str = fr'mssql+pymssql://{domain}\{username}:{password}#{hostip}/{db}'
engine = create_engine(eng_str)
What changed was to add the Windows domain before \username.
You'll need to install the pymssql package.

Create Your SqlAlchemy Connection URL      From Your pyodbc Connection String      OR Your Known Connection Parameters
I found all the other answers to be educational, and I found the SqlAlchemy Docs on connection strings helpful too, but I kept failing to connect to MS SQL Server Express 19 where I was using no username or password and trusted_connection='yes' (just doing development at this point).
Then I found THIS method in the SqlAlchemy Docs on Connection URLs built from a pyodbc connection string (or just a connection string), which is also built from known connection parameters (i.e. this can simply be thought of as a connection string that is not necessarily used in pyodbc). Since I knew my pyodbc connection string was working, this seemed like it would work for me, and it did!
This method takes the guesswork out of creating the correct format for what you feed to the SqlAlchemy create_engine method. If you know your connection parameters, you put those into a simple string per the documentation exemplified by the code below, and the create method in the URL class of the sqlalchemy.engine module does the correct formatting for you.
The example code below runs as is and assumes a database named master and an existing table named table_one with the schema shown below. Also, I am using pandas to import my table data. Otherwise, we'd want to use a context manager to manage connecting to the database and then closing the connection like HERE in the SqlAlchemy docs.
import pandas as pd
import sqlalchemy
from sqlalchemy.engine import URL
# table_one dictionary:
table_one = {'name': 'table_one',
'columns': ['ident int IDENTITY(1,1) PRIMARY KEY',
'value_1 int NOT NULL',
'value_2 int NOT NULL']}
# pyodbc stuff for MS SQL Server Express
driver='{SQL Server}'
server='localhost\SQLEXPRESS'
database='master'
trusted_connection='yes'
# pyodbc connection string
connection_string = f'DRIVER={driver};SERVER={server};'
connection_string += f'DATABASE={database};'
connection_string += f'TRUSTED_CONNECTION={trusted_connection}'
# create sqlalchemy engine connection URL
connection_url = URL.create(
"mssql+pyodbc", query={"odbc_connect": connection_string})
""" more code not shown that uses pyodbc without sqlalchemy """
engine = sqlalchemy.create_engine(connection_url)
d = {'value_1': [1, 2], 'value_2': [3, 4]}
df = pd.DataFrame(data=d)
df.to_sql('table_one', engine, if_exists="append", index=False)
Update
Let's say you've installed SQL Server Express on your linux machine. You can use the following commands to make sure you're using the correct strings for the following:
For the driver: odbcinst -q -d
For the server: sqlcmd -S localhost -U <username> -P <password> -Q 'select ##SERVERNAME'

pyodbc
I think that you need to put:
"+pyodbc" after mssql
try this:
from sqlalchemy import create_engine
engine = create_engine("mssql+pyodbc://user:password#host:port/databasename?driver=ODBC+Driver+17+for+SQL+Server")
cnxn = engine.connect()
It works for me
Luck!

If you are attempting to connect:
DNS-less
Windows Authentication for a server not locally hosted.
Without using ODBC connections.
Try the following:
import sqlalchemy
engine = sqlalchemy.create_engine('mssql+pyodbc://' + server + '/' + database + '?trusted_connection=yes&driver=SQL+Server')
This avoids using ODBC connections and thus avoids pyobdc interface errors from DPAPI2 vs DBAPI3 conflicts.
I would recommend using the URL creation tool instead of creating the url from scratch.
connection_url = sqlalchemy.engine.URL.create("mssql+pyodbc",database=databasename, host=servername, query = {'driver':'SQL Server'})
engine = sqlalchemy.create_engine(connection_url)
See this link for creating a connection string with SQL Server Authentication (non-domain, uses username and password)