codesnips

postgres

python 
from alembic import op
import sqlalchemy as sa

revision = "20240612_add_status"
down_revision = "20240515_create_orders"
branch_labels = None

Zero-Downtime NOT NULL Column Backfill with Alembic and SQLAlchemy

alembic sqlalchemy migrations
by codesnips 2 tabs
ruby 
class Product < ApplicationRecord
  scope :by_status, ->(status) {
    status.present? ? where(status: status) : all
  }

  scope :in_category, ->(category_id) {

Composable Query Filters with Rails Scopes and a Filter Object

rails activerecord scopes
by codesnips 3 tabs
ruby 
class LastSeenTracker
  THROTTLE = 5.minutes
  PENDING_KEY = "pending:last_seen".freeze

  class << self
    def touch(user_id, at: Time.current)

Database “Last Seen” without Hot Row Updates

rails performance redis
by codesnips 3 tabs
python 
import base64
import json
from datetime import datetime
from typing import NamedTuple

from fastapi import HTTPException

Cursor-Based Pagination in FastAPI with a Dependency and RFC 5988 Link Headers

fastapi pagination cursor
by codesnips 3 tabs
java 
package com.example.catalog.web;

import com.example.catalog.domain.Product;
import java.math.BigDecimal;

public record ProductResponse(

Paginated Product Search Endpoint with Spring Data JPA Specifications

spring-boot spring-data-jpa pagination
by codesnips 4 tabs
python 
import hashlib
from datetime import datetime, timezone

from sqlalchemy import BigInteger, Column, DateTime, String, UniqueConstraint
from sqlalchemy.orm import declarative_base

Efficient Bulk Insert in SQLAlchemy with a Reusable Chunking Helper

sqlalchemy postgres bulk-insert
by codesnips 3 tabs
ruby 
class CreateReservations < ActiveRecord::Migration[7.1]
  def up
    enable_extension "btree_gist" unless extension_enabled?("btree_gist")

    create_table :reservations do |t|
      t.references :room, null: false, foreign_key: true

DB-Level “no overlapping ranges” with exclusion constraint

rails postgres exclusion-constraint
by codesnips 3 tabs
rust 
use sqlx::PgPool;
use std::time::Duration;
use tokio::sync::mpsc;

#[derive(Debug, Clone)]
pub struct MetricPoint {

Batching Database Writes in Rust with a Size- and Interval-Triggered Flush Buffer

rust tokio sqlx
by codesnips 3 tabs
go 
package bank

import "errors"

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

Optimistic Locking in Go With a Version Column on UPDATE

optimistic-locking concurrency postgres
by codesnips 3 tabs
erb 
<%= form_with url: bulk_update_orders_path, method: :patch, data: { turbo_confirm: "Update selected orders?" } do %>
  <div class="batch-toolbar">
    <%= select_tag :status,
          options_for_select(Order.statuses.keys.map { |s| [s.humanize, s] }),
          prompt: "Set status to\u2026" %>
    <%= submit_tag "Apply to selected", class: "btn" %>

Bulk-Updating Order Statuses with a Checkbox Collection and update_all Batch Action in Rails

rails activerecord update-all
by codesnips 3 tabs
ruby 
class Coupon < ApplicationRecord
  before_validation :normalize_code

  validates :code,
            coupon_code: { min_length: 6 },
            uniqueness: { case_sensitive: false }

Validating Coupon Codes with a Custom EachValidator in Rails

rails validations activerecord
by codesnips 3 tabs
ruby 
class DashboardMetrics
  include ActiveModel::Model

  attr_reader :account

  def initialize(account)

Expiring Dashboard Fragment Caches with a Versioned Composite Cache Key in Rails

rails caching fragment-caching
by codesnips 3 tabs