Is SQLAlchemy thread-safe?
Every pool implementation in SQLAlchemy is thread safe, including the default QueuePool. This means that 2 threads requesting a connection simultaneously will checkout 2 different connections. By extension, an engine will also be thread-safe.
Should I use the bulk methods in SQLAlchemy?
It is strongly recommended to not use the bulk methods as they represent a forking of SQLAlchemy’s functionality and are slowly being moved into legacy status. New features such as Using INSERT, UPDATE and ON CONFLICT (i.e. upsert) to return ORM Objects are both more efficient than the “bulk” methods and provide more predictable functionality.
Does SQLAlchemy recommend to separate session creation from database query?
* Although it is not enforced by SQLAlchemy, it does recommended to separate individual db operations from session creation. That is, it recommends not create sessions right next to where you make a single database query. We will try to follow this pattern recommendation blindly.
What features are not supported in SQLAlchemy?
Features such as object management, relationship handling, and SQL clause support are silently omitted in favor of raw UPDATES of records. Please note that newer versions of SQLAlchemy are greatly improving the efficiency of the standard flush process.
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Is SQLAlchemy good for ETL?
One of the key aspects of any data science workflow is the sourcing, cleaning, and storing of raw data in a form that can be used upstream. This process is commonly referred to as “Extract-Transform-Load,” or ETL for short.
Is SQLAlchemy worth using?
SQLAlchemy is the ORM of choice for working with relational databases in python. The reason why SQLAlchemy is so popular is because it is very simple to implement, helps you develop your code quicker and doesn't require knowledge of SQL to get started.
Does SQLAlchemy automatically close connection?
connect() method returns a Connection object, and by using it in a Python context manager (e.g. the with: statement) the Connection. close() method is automatically invoked at the end of the block.
Can SQLAlchemy be used without flask?
One of the most sought after helpers being the handling of a database connection across the app. However, ensuring your database connection session is available throughout your app can be accomplished with base SQLAlchemy and does not require Flask-SQLAlchemy.
Is SQLAlchemy used in industry?
It enables you to create data models and queries in a manner that feels like normal Python classes and statements. Created by Mike Bayer in 2005, SQLAlchemy is used by many companies great and small, and is considered by many to be the de facto way of working with relational databases in Python.
Do companies use SQLAlchemy?
SQLAlchemy is most often used by companies with 50-200 employees and 1M-10M dollars in revenue.
Does SQLAlchemy use a connection pool?
SQLAlchemy includes several connection pool implementations which integrate with the Engine . They can also be used directly for applications that want to add pooling to an otherwise plain DBAPI approach.
What creates SQLAlchemy Engine?
The Engine is the starting point for any SQLAlchemy application. It's “home base” for the actual database and its DBAPI, delivered to the SQLAlchemy application through a connection pool and a Dialect , which describes how to talk to a specific kind of database/DBAPI combination.
How do I rollback SQLAlchemy?
Using SAVEPOINT commit() method on this object is called, “RELEASE SAVEPOINT” is emitted to the database, and if instead the . rollback() method is called, “ROLLBACK TO SAVEPOINT” is emitted. The enclosing database transaction remains in progress.
Is Flask-SQLAlchemy thread safe?
Every pool implementation in SQLAlchemy is thread safe, including the default QueuePool . This means that 2 threads requesting a connection simultaneously will checkout 2 different connections. By extension, an engine will also be thread-safe.
What is the difference between sqlite and SQLAlchemy?
Sqlite is a database storage engine, which can be better compared with things such as MySQL, PostgreSQL, Oracle, MSSQL, etc. It is used to store and retrieve structured data from files. SQLAlchemy is a Python library that provides an object relational mapper (ORM).
Which one is better Django or Flask?
Flask is considered more “Pythonic” than Django is basically since Flask web application code is, in most cases, more unequivocal. Flask is the choice of most tenderfoots due to the need of barricades to getting a basic app up and running.
What are the major benefits of using SQLAlchemy?
Main advantages of SQLAlchemy toolkitNo ORM Required.Varied databases support.Unit Of Work.Mature, High Performing Architecture.DBA Approved Non-Opinionated.Function-based query construction.Separate mapping and class design.Composite (multiple-column) primary keys.More items...
What is the point of SQLAlchemy?
SQLAlchemy is a library that facilitates the communication between Python programs and databases. Most of the times, this library is used as an Object Relational Mapper (ORM) tool that translates Python classes to tables on relational databases and automatically converts function calls to SQL statements.
Is SQLAlchemy faster than psycopg2?
The psycopg2 is over 2x faster than SQLAlchemy on small table. This behavior is expected as psycopg2 is a database driver for postgresql while SQLAlchemy is general ORM library.
What companies use SQLAlchemy?
The Python SQL Toolkit and Object Relational MapperYelp!reddit.DropBox.The OpenStack Project.Survey Monkey.
What is thread safe in Python?
Threads in python share memory: so if an object is modified in a thread, this change is reflected in the other. An object or a function is said to be thread-safe if concurrent access or modification by different threads is possible and the behavior is still normal.
What does sqlalchemy.exc.OperationalError mean?
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request.
Is a thread safe engine?
By extension, an engine will also be thread-safe. Most of the time in a web application, you would want to share the pool with all the threads in the same process, so that the maximum number of opened connections doesn’t depend on the number of threads configured in your WSGI server.
Can you use the same connection in multiple threads?
Ultimately, the important fact is that you must not use the same connections from multiple threads or processes. To make sure this is not the case, here are a couple things you might want to try:
Is a connection object thread safe?
However, both the Connection object and the Session object are not thread-safe. Concurrent usage of any in multiple threads will lead to race conditions.
Is the script imported before forking?
This script is imported before the forking takes place. The fact that we made a query before forking is problematic, because now the duplicated pool inside the 2 workers think they are responsible for the same connection.
Tuesday Daily Thread: Advanced questions
Have some burning questions on advanced Python topics? Use this thread to ask more advanced questions related to Python.
I just wanted to share a script I've made to my dad
I've been learning python since January this year but never made a "useful" project. So my dad uses excel to keep track of his investments but has to update the stocks prices by hand, which takes a while.
How The Default Pooling Works
Using Multiple Threads
- Threads in python share memory: so if an object is modified in a thread, this change is reflected in the other. An object or a function is said to be thread-safe if concurrent access or modification by different threads is possible and the behavior is still normal. Every pool implementation in SQLAlchemy is thread safe, including the default QueueP...
How Multiple Processes Can Go Wrong
- Processes don’t share memory in python (well, not before python 3.8, but that’s another story). There is although an important thing to consider: when the process is forked, the default multiprocessing mode on Unix, every object in memory at that point is copied. This means that if an object holds a reference to a resource (say, a database connection), this reference is also co…
An Example Using Flask and Gunicorn
- Here is a sample app that uses flask. Notice I explicitly set the pool_size to 5 and the max_overflow to 10, but these are the default arguments when nothing is provided to the create_enginefunction. This means that no more than 15 connections can be opened at the same time using this engine instance (with 5 of them staying idle when not in use, and 10 of them bein…
Takeaways and Solutions
- Ultimately, the important fact is that you must not use the same connections from multiple threads or processes. To make sure this is not the case, here are a couple things you might want to try: 1. Notice when the engine creation takes place: you most likely want to have it shared as a global object after forking. 2. Notice when forking takes place. This can depend which libraries y…