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Matches found for tag 'SQLAlchemy': 9, showing 8

Using UUIDs instead of Integer Autoincrement Primary Keys with SQLAlchemy and MariaDb

9 April 2020 Updated 9 April 2020 by Peter

We all know the Integer Autoincrement Primary Key. Works great, much software is doing it this way. It is fast. But it also has limitations. An alternative for the Integer Autoincrement Primary Key is the UUID (Universally Unique IDentifier) Primary Key. A UUID is a 128-bit number. It can be represented by a string, for example: 05390f2b-48e8-45c7-8ae4-08272dc69122 or a hex string (the same as above ...
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Threaded comments using Common Table Expressions (CTE) for a MySQL Flask blog or CMS

8 February 2020 Updated 16 February 2020 by Peter

Now that I have blog posts, pages and a contact form, I decided to implement the comments for the blog posts and pages. Not just flat comments but threaded comments, also called nested comments. Some months ago I read about this and I really liked Miguel Grinberg's article: Implementing User Comments with SQLAlchemy. As often Miguel starts with defining the problem and some hard core theory and explaining ...
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Reducing page response times of a Flask SQLAlchemy website

29 August 2019 Updated 30 August 2019 by Peter

Objects, it is nice to build an application with them but it has one very big disadvantage: it can be very slow because of the extra CPU-cycles and all the extra memory used. The slowdown of course is very much caused by the extra mapper layers and extra data. Should you care about performance? Yes! The admin part of an application does not have to be very fast but the frontend pages, the pages ...
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Converting to a multilanguage database

25 August 2019 Updated 30 August 2019 by Peter

When I started this project, this website, I kept in mind that it had to support multiple languages. But of course I did not really look into database design because of all the other things I had to learn, add and implement. After a certain moment I could display and select multiple languages but that was for the texts in the code and templates and not for the database content items like blog posts ...
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Flask + SQLAlchemy + MariaDB profiling

29 July 2019 Updated 29 August 2019 by Peter

Performance is a never ending story. At a certain moment I noticed that putting the home page on the screen took some 370 milliseconds using the Flask development server with debug messages shown. That seemed far too long! How did I notice this? Because at the bottom of every page I show the time it takes to generate a page. Please note that the timings below are from a more optimized version of the ...
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SQLAlchemy server-side datetime calculations

24 June 2019 Updated 31 August 2019 by Peter

You will find a lot of SQLAlchemy datetime calculation examples using e.g. Python's timedelta function. Why? I do not understand this except that this is easy. But is it correct? Assume we we want all user records or objects created two hours ago and the record / object definition is: class User(Base): __tablename__ = 'user' id = Column(Integer, primary_key=True) created_on ...
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SLQAlchemy dynamic query building and filtering including soft deletes

21 June 2019 Updated 29 August 2019 by Peter

Building on the previous post 'Flask, Jinja2 and SLQAlchemy many-to-many relationship with conditions' I looked for a way to dynamically add filter conditions and if possible also find a solution for the soft delete pattern. Soft delete is not deleting records from a table but instead marking them as deleted. This means that every table must have a deleted flag and all queries must exclude records ...
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Flask, Jinja2 and SLQAlchemy many-to-many relationship with conditions

17 June 2019 Updated 31 August 2019 by Peter

Disclaimer: This my first SQLAlchemy project so I am not experienced and may make wrong statements in this post. While working on my first Flask / SQLAchemy project (I do not use Flask-SQLAlchemy) I hit a very high and thick wall. To explain this, consider you have a blog with posts and tags. There is a many-to-many relationship between posts and tags: a post can have many tags and a tag can have ...
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