database

package bank

import "errors"

var ErrVersionConflict = errors.New("optimistic lock: version conflict")
var ErrInsufficientFunds = errors.New("insufficient funds")

class CreateComments < ActiveRecord::Migration[6.1]
  def change
    create_table :comments do |t|
      t.references :commentable, polymorphic: true, null: false
      t.references :author, null: false, foreign_key: { to_table: :users }
      t.text :body, null: false

; PgBouncer configuration file

[databases]
; Database connection strings
mydb = host=localhost port=5432 dbname=mydb
analytics = host=replica.example.com port=5432 dbname=mydb

from django.db import transaction
from django.shortcuts import get_object_or_404
from django.http import JsonResponse
from .models import Product

require 'activerecord-import'

class BulkImportPostsService
  BATCH_SIZE = 1000

  def initialize(csv_file_path)

package com.example.myapp.data.local

import android.content.Context
import androidx.room.*
import androidx.sqlite.db.SupportSQLiteDatabase
import kotlinx.coroutines.CoroutineScope

-- Primary server configuration (postgresql.conf)
-- wal_level = replica
-- max_wal_senders = 10
-- wal_keep_size = 64MB
-- hot_standby = on

class AddLockVersionToPosts < ActiveRecord::Migration[6.1]
  def change
    add_column :posts, :lock_version, :integer, default: 0, null: false
  end
end

-- Migration naming convention: V{version}__{description}.sql
-- Example: V001__create_users_table.sql

-- Migration 1: Create initial schema
-- V001__create_users_table.sql
CREATE TABLE users (

production:
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS", 5) %>
  timeout: 5000
  checkout_timeout: 5

class AddMetadataToUsers < ActiveRecord::Migration[6.1]
  def change
    add_column :users, :metadata, :jsonb, default: {}, null: false
    add_index :users, :metadata, using: :gin
  end
end