bharath-kotha

from celery import Celery
from datetime import datetime                                                              

app = Celery('tasks')
# Setting the task_always_eager to to true for demonstrating the issue
# You don't want to set it to true in production environments
app.conf.task_always_eager = True

def convert_to_iso(timestamp):
    ''' Convert Unix timestamp to an ISO string

bharath-kotha

CREATE TABLE author (
    id bigserial primary key, 
    name varchar(64) not null, country varchar(64)
);

CREATE TABLE book (
    id bigserial primary key, 
    title varchar(128) not null, 
    author_id bigint NOT NULL, 
    CONSTRAINT fk_books_author_id FOREIGN KEY (author_id) REFERENCES author(id)

bharath-kotha

import random

NUM_AUTHORS = 10000000
NUM_BOOKS = 20000000

# Any author can wite any book
author_sql = """INSERT INTO author (id, name) values ({i}, 'author_{i}');\n"""
book_sql = """INSERT INTO book (title, author_id) values ('title_{i}', {author_id});\n"""

data_file = open('data.sql', 'w')

bharath-kotha

                                                                QUERY PLAN                                                                 
-------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.87..51.28 rows=100 width=206) (actual time=0.023..24.739 rows=100 loops=1)
   Buffers: shared hit=255 read=149
   ->  Nested Loop  (cost=0.87..10080882.37 rows=20000000 width=206) (actual time=0.023..24.714 rows=100 loops=1)
         Buffers: shared hit=255 read=149
         ->  Index Scan using book_pkey on book  (cost=0.44..666418.44 rows=20000000 width=30) (actual time=0.012..0.069 rows=100 loops=1)
               Buffers: shared hit=4
         ->  Index Scan using author_pkey on author  (cost=0.43..0.47 rows=1 width=168) (actual time=0.245..0.245 rows=1 loops=100)
               Index Cond: (id = book.author_id)

bharath-kotha

                                                                         QUERY PLAN                                                                          
-------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=1038449.15..1038460.82 rows=100 width=206) (actual time=23225.822..26199.674 rows=100 loops=1)
   Buffers: shared hit=9749 read=201159, temp read=182633 written=195896
   ->  Gather Merge  (cost=1038449.15..2983029.28 rows=16666666 width=206) (actual time=23225.820..26199.659 rows=100 loops=1)
         Workers Planned: 2
         Workers Launched: 2
         Buffers: shared hit=9749 read=201159, temp read=182633 written=195896
         ->  Sort  (cost=1037449.13..1058282.46 rows=8333333 width=206) (actual time=23219.185..23219.219 rows=75 loops=3)
               Sort Key: book.title, book.id