vskrachkov

"""
    base_werkzeug_app.py
    ====================

    Example of a simple app written using werkzeug library.
"""
import json

import psycopg2
from werkzeug.exceptions import HTTPException

vskrachkov

"""
    class_property.py
    =================

    Shows how to use python's built-in class 'property' for implementation of
    encapsulation by pythonic way.

    Use 'python3 -i class_property' for testing Man class interfaces.
    Instance of this class will be already initialized as 'man' variable.

vskrachkov

def bubble_sort(a_list):
    """Realizes a bubble sort algorithm.
    Time complexity: O(n^2)
    """
    for one_pass in range(len(a_list)-1):
        for i in range(len(a_list)-1):
            if a_list[i] > a_list[i+1]:
                a_list[i], a_list[i+1] = a_list[i+1], a_list[i]
    return a_list

vskrachkov

select t.table_schema, t.table_name,
  'TRUNCATE public.' || t.table_name || ' CASCADE;', 'insert into public.'
  || t.table_name || '(' || string_agg(c.column_name, ',') || ') select ' || string_agg(c.column_name, ',') || ' from '
  || 'main.' || substring(t.table_name from 6) || ';'
from information_schema.columns c
  join information_schema.tables t on t.table_name = c.table_name and t.table_schema = 'public'
where t.table_schema in ('public') and t.table_type = 'BASE TABLE'
GROUP BY t.table_schema, t.table_name;

vskrachkov

SELECT
     n.nspname  as "schema"
    ,t.relname  as "table"
    ,c.relname  as "index"
    ,i.indisunique AS "is_unique"
    ,array_to_string(array_agg(a.attname), ', ') as "columns"
    ,pg_get_indexdef(i.indexrelid) || ';' as "ddl"
    ,'DROP INDEX ' || n.nspname || '.' || c.relname || ';' as "delete_ddl"
FROM pg_catalog.pg_class c
    JOIN pg_catalog.pg_namespace n ON n.oid        = c.relnamespace

vskrachkov

SELECT
    tc.constraint_name, tc.table_name, kcu.column_name,
    ccu.table_name AS foreign_table_name,
    ccu.column_name AS foreign_column_name
FROM
    information_schema.table_constraints AS tc
    JOIN information_schema.key_column_usage AS kcu
      ON tc.constraint_name = kcu.constraint_name
    JOIN information_schema.constraint_column_usage AS ccu
      ON ccu.constraint_name = tc.constraint_name

vskrachkov

/******************************************************************************
    Current example realize many-to-many relationship between product and
    customer's purchase order on it in PostgreSQL DBMS.
    +~~~~~~~~~+        +~~~~~~~~~~~~~~~~~~~+        +~~~~~~~~~~~~~~~~~~~+
    |*product*|        |   *order_items*   |        |  *purchase_order* |
    +~~~~~~~~~+        +~~~~~~~~~~~~~~~~~~~+        +~~~~~~~~~~~~~~~~~~~+
    | id      |  _____ | product_id        |    __  | id                |
    +---------+        +-------------------+   /    +-------------------+
    | name    |        | purchase_order_id | _/     | customer_address  |
    +---------+        +-------------------+        +-------------------+

vskrachkov

SELECT 'SELECT setval(''main_' || c.relname || ''', nextval(''' || n.nspname || '.' || c.relname || ''') + 20);' FROM pg_class c
  JOIN pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind = 'S' and n.nspname = 'main';

vskrachkov

def discover(package_name):
    """Function that discovers packages for django.
    For example, if you want store your models in different files you must
    call this function in __init__ file of the models package.
    
    Django app structure:
        some_app/
            __init__.py
            models/
                my_model.py

vskrachkov

def register_all(app_label):
    """Function for django admin.
    Register all app models in django admin.
    """
    from django.apps import apps
    from django.contrib import admin
    from django.contrib.admin.sites import AlreadyRegistered

    app_models = apps.get_app_config(app_label).get_models()
    for model in app_models: