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Evgenij Legotskoj

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Evgenij LegotskojApril 18, 2022, 5:39 p.m.

DjangoDjango - Tutorial 058. Database Growth Due to django_session Table

Django, Postgres, garbage collection, Python, PostgreSQL

Lately, I have noticed that the fatal moment is approaching, when the disk space for the site on the hosting will catastrophically cease to be enough. And the database dump becomes incredibly huge, although there are no obvious prerequisites for this. The content size of the site isn't growing that fast, and the number of registered users isn't growing that fast either.

After examining the database, it was found that the size of the django_session table is just a gigantic almost 7 GB, and the size of the index also reaches almost 6.5 GB, despite the fact that the size of the database itself is 14 GB.

At the same time, the size of the second largest table is only 11 MB and this is a third-party application with a list of cities. And the size of the third table, which contains messages on the forum, is only 8 MB.

Accordingly, it was decided to figure out why this is happening and how to fix it.

Right now, I probably won’t reveal anything new to those who actively administer PostgreSQL databases, but for beginners and those who mainly deal with Django as a PET project, without professional use, the information may be useful.

Evgenij LegotskojFeb. 14, 2022, 4:24 a.m.

DjangoDjango Rest Framework - Tutorial 001. Adding Token Authentication

Django Rest Framework, QML, Authentication, Token, drf, Felgo

At the moment I am actively working on an application that will work with the REST API of a Django site. And one of the first steps was to set up user authentication by token, but in order for this to work, you must first obtain an authorization token.

Let's look at how this can be done.

Evgenij LegotskojFeb. 10, 2022, 4:13 a.m.

DjangoDjango - Lesson 057. Multilanguage support in MarkdownField with auto populate functionality

MarkdownField, markdown, modeltranslation, Django

The article How to write auto populate field functionality described the simplest functionality of the MarkdownField field to support markdown syntax on a site with automatic generation of html content.

I did not immediately show advanced functionality to make it easier to understand what a Markdown-like field is like. But now I would like to expand this functionality to add support for multilingualism.

Evgenij LegotskojFeb. 9, 2022, 6:11 a.m.

DjangoDjango - Tutorial 056. How to convert image to WEBP format when saving to ImageField

ImageField, Django, WEBPField, webp, Python

WEBP is an image compression format that was introduced by Google in 2010. Its main advantage is its low size without visible loss of quality compared to formats such as JPEG or PNG. Therefore, it is quite logical to use this format for storing images on the site, especially if you do not need to store the original images on the site.

After a long search, I still did not find a ready-made and simple solution that would support converting images to WEBP format on the fly.
Therefore, I decided to write my own version, which eventually consists of a couple of dozen lines and is as simple as a wooden board.

Evgenij LegotskojFeb. 8, 2022, 6:55 a.m.

DjangoDjango - Tutorial 055. How to write auto populate field functionality

field, Django, python, auto, Python

For a long time I wanted to write an article on how to write auto populate field functionality for a Django project. This is a very useful feature that allows you to change the content of other model fields in Django by setting a value to a field that uses auto populate.

First, why is it needed? - Such functionality allows you to reduce the size of the code in those places where you need to rewrite other fields of the object when they change. That is, for example, you do not have to redefine the save method each time in order to rewrite some field in case other fields of the object change. Also, using auto populate is basically a more advanced and neat way to manage data models in Django.
And also a similar approach can solve some problems and improve the site.

Evgenij LegotskojFeb. 7, 2022, 8:52 a.m.

QtQt/C++ Tutorial 092. Creating translations for external text sources

Qt 6, Qt, Qt 5, QtLinguist, translation

Today we will discuss a rather interesting option for adding translation to a Qt/C++ application. Namely, adding translations for texts from external sources when you display texts from databases, an external API, or just some other files.

Such a situation can arise in the following case, for example, analysts in your project form sets of data and texts in some external database or text files, but there is no possibility of multilingualism for some reason. And therefore, you do not have the option to select the language as an additional parameter when requesting this data. Or, for example, the final data is downloaded from an external resource and stored in a SQLite database, of course, without additional translations. But at the same time, you are developing a multilingual application and you need to somehow generate translation files for these texts, so that the translation team can translate them, and you can connect them in the application.

But in Qt it is possible to solve this problem as well. In such situations, you can also generate source code files in the same way, for example, generate them when importing data during application development, and then generate translation files with the extension *.ts , which are used in QtLinguist to translate the application to Qt, and then generate binary *.qm translation files that will be included in the application.

Let's see how it works and what needs to be done for this.

Evgenij LegotskojDec. 31, 2020, 7:05 a.m.

EVILEGHappy New Year to all EVILEG Community !!!

Дорогие пользователи EVILEG!

Поздравляю Вас с наступающим Новым Годом!!!
Желаю счастья, здоровья и успехов в программировании в новом 2021 году!!!

Evgenij LegotskojJuly 21, 2020, 2:31 a.m.

C++Method call on nullptr

UB, nullptr, cpp

Let's take a look at a small code example when a method is called on an object that is initialized with nullptr .

Evgenij LegotskojJune 3, 2020, 5:30 p.m.

QtQt/C++ - Tutorial 091. How to write a custom delegate controlling the highlighting of a row in a table

Qt, QTableView, Delegate

And now a short article on customizing cell behavior using delegates in a QTableView.
This article is a modification of the table behavior in one old article, namely Qt/C ++ - Tutorial 039. How to fill a row in QSqlTableModel by the value in the column . In fact, that old article has no effect on the contents of this article, but the table for an example will be taken from that lesson.

As the task, the color of the line was selected when the mouse cursor was over.

It will look as follows

Evgenij LegotskojMay 13, 2020, 5:42 a.m.

Python 3Python Image Recognition with TensorFlow and Keras

Keras, python, RuCaptcha, TensorFlow

Introduction

One of the most common uses of TensorFlow and Keras is in image recognition and classification. If you would like to learn how to use Keras for image classification or recognition, this article will teach you how to do it.

Definitions

If you do not understand the basic concepts of image recognition, it will be difficult for you to fully understand the main part of this article. Therefore, before we continue, let's define the terminology.

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