EXASOL dialect for SQLAlchemy
Project description
How to get started
We assume you have a good understanding of (unix)ODBC. If not, make sure you read their documentation carefully - there are lot’s of traps 🪤 to step into.
Meet the system requirements
On Linux/Unix like systems you need:
Python
An Exasol DB (e.g. docker-db or a cloud instance)
The packages unixODBC and unixODBC-dev >= 2.2.14
The Exasol ODBC driver
The ODBC.ini and ODBCINST.ini configurations files setup
Turbodbc support
You can use Turbodbc with sqlalchemy_exasol if you use a python version >= 3.8.
Multi row update is not supported, see test/test_update.py for an example
Setup your python project and install sqlalchemy-exasol
$ pip install sqlalchemy-exasol
for turbodbc support:
$ pip install sqlalchemy-exasol[turbodbc]
Talk to the EXASOL DB using SQLAlchemy
from sqlalchemy import create_engine
url = "exa+pyodbc://A_USER:A_PASSWORD@192.168.1.2..8:1234/my_schema?CONNECTIONLCALL=en_US.UTF-8&driver=EXAODBC"
e = create_engine(url)
r = e.execute("select 42 from dual").fetchall()
to use turbodbc as driver:
from sqlalchemy import create_engine
url = "exa+turbodbc://A_USER:A_PASSWORD@192.168.1.2..8:1234/my_schema?CONNECTIONLCALL=en_US.UTF-8&driver=EXAODBC"
e = create_engine(url)
r = e.execute("select 42 from dual").fetchall()
The dialect supports two types of connection urls creating an engine. A DSN (Data Source Name) mode and a host mode:
Type |
Example |
DSN URL |
‘exa+pyodbc://USER:PWD@exa_test’ |
HOST URL |
‘exa+pyodbc://USER:PWD@192.168.14.227..228:1234/my_schema?parameter’ |
Features
SELECT, INSERT, UPDATE, DELETE statements
you can even use the MERGE statement (see unit tests for examples)
Notes
Schema name and parameters are optional for the host url
At least on Linux/Unix systems it has proven valuable to pass ‘CONNECTIONLCALL=en_US.UTF-8’ as a url parameter. This will make sure that the client process (Python) and the EXASOL driver (UTF-8 internal) know how to interpret code pages correctly.
Always use all lower-case identifiers for schema, table and column names. SQLAlchemy treats all lower-case identifiers as case-insensitive, the dialect takes care of transforming the identifier into a case-insensitive representation of the specific database (in case of EXASol this is upper-case as for Oracle)
As of Exasol client driver version 4.1.2 you can pass the flag ‘INTTYPESINRESULTSIFPOSSIBLE=y’ in the connection string (or configure it in your DSN). This will convert DECIMAL data types to Integer-like data types. Creating integers is a factor three faster in Python than creating Decimals.
Development & Testing
See developer guide
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