A Pokemon Crash Course on CouchDB

This tutorial provides a practical guide to using CouchDB, a NoSQL database, via its HTTP API with PHP. We'll skip the theoretical aspects and dive straight into performing database operations. We assume you have CouchDB and Futon (its web admin console) already set up.

Note: We use localhost for simplicity. If using a VM, adjust accordingly (e.g., using a custom vhost and forwarded ports).

Key Concepts:

• CouchDB Basics: A NoSQL database using JSON for storage, JavaScript for queries, and an HTTP API.
• Document Structure: Data is stored in individual JSON documents; no fixed schema or tables.
• HTTP API: Use HTTP requests (GET, POST, PUT, DELETE) to interact with the database.
• PHP Integration: We'll demonstrate using Guzzle and Doctrine's CouchDB Client.
• Advanced Features (briefly mentioned): MapReduce, conflict resolution, change feeds.

Creating a Database:

Use Futon (https://www.php.cn/link/3bbbc60ff463969b78a091ff51ac6566) to create a database. Give it a name (e.g., test_couch).

After creation, you'll see an interface to add documents. Remember, in CouchDB, documents are the fundamental unit; there are no tables. You can store different data structures within the same database. For organization, include a type field to categorize documents (e.g., "type": "users").

Example Document Structures:

• User: {"id": 123, "fname": "doppo", "lname": "kunikida", "pw": "secret", "hobbies": ["reading", "sleeping"], "type": "users"}
• Blog Post: {"title": "The big brown fox", "author": "fox", "text": "...", "publish_date": "2016-07-07", "type": "blog_posts"}

HTTP API Interaction:

You can use curl or tools like Postman to interact directly with the CouchDB HTTP API.

• Create Database (curl): curl -X PUT http://localhost:5984/<database_name></database_name> (returns {"ok":true})
• Create Document (Postman): Send a POST request to http://localhost:5984/test_couch, with Content-Type: application/json and your JSON document in the body.

Bulk Insert:

Use a POST request to http://localhost:5984/test_couch/_bulk_docs with an array of documents in the JSON body.

Retrieving Documents:

• All Documents: http://localhost:5984/test_couch/_all_docs?include_docs=true
• Specific Document: http://localhost:5984/test_couch/<document_id>?include_docs=true</document_id>
• Specific Revision: Add &rev=<revision_id></revision_id> to the URL above.

CouchDB tracks revisions; each update creates a new revision. Futon allows browsing through these revisions.

Views (MapReduce):

Views provide querying capabilities. Create views in Futon using map and reduce functions (JavaScript). These functions are saved within design documents.

• Example Map Function (filter by trainer):

<code class="language-javascript">function(doc) {
  emit(doc.trainer, doc.name);
}</code>

Access views via URLs like: http://localhost:5984/test_couch/_design/<design_doc>/_view/<view_name>?key="Ash"</view_name></design_doc>

Updating Documents:

Send a PUT request to the document URL, including the _rev field with the latest revision ID. You must provide the entire updated document.

Deleting Documents:

Send a DELETE request to the document URL, including the _rev field with the latest revision ID.

http://localhost:5984/test_couch/<document_id>?rev=<revision_id></revision_id></document_id>

PHP Integration (Guzzle):

Guzzle simplifies HTTP requests in PHP. The following examples demonstrate basic operations: (Remember to install Guzzle: composer require guzzlehttp/guzzle)

<code class="language-php"><?php
require 'vendor/autoload.php';
use GuzzleHttp\Client;

$client = new Client(['base_uri' => 'http://localhost:5984']);

// ... (GET, POST, PUT, DELETE examples using Guzzle similar to the curl and Postman examples above) ...
?></code>

PHP Integration (Doctrine CouchDB Client):

Doctrine's CouchDB client provides a higher-level abstraction. (Install with: composer require doctrine/couchdb)

<code class="language-php"><?php
require 'vendor/autoload.php';

$client = \Doctrine\CouchDB\CouchDBClient::create(['dbname' => 'test_couch']);

// ... (Examples for creating, retrieving, updating, and deleting documents using the Doctrine client) ...
?></code>

Conclusion:

This tutorial offers a practical introduction to CouchDB using its HTTP API and PHP. Explore the official documentation and the Definitive Guide for more advanced features. Future posts will delve deeper into building applications with CouchDB.

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