Elasticsearch Query and ActiveRecord for Yii 2
==============================================

This extension provides the [elasticsearch](http://www.elasticsearch.org/) integration for the Yii2 framework.
It includes basic querying/search support and also implements the `ActiveRecord` pattern that allows you to store active
records in elasticsearch.

To use this extension, you have to configure the Connection class in your application configuration:

```php
return [
	//....
	'components' => [
        'elasticsearch' => [
            'class' => 'yii\elasticsearch\Connection',
            'nodes' => [
                ['http_address' => '127.0.0.1:9200'],
                // configure more hosts if you have a cluster
            ],
        ],
	]
];
```


Installation
------------

The preferred way to install this extension is through [composer](http://getcomposer.org/download/).

Either run

```
php composer.phar require --prefer-dist yiisoft/yii2-elasticsearch "*"
```

or add

```json
"yiisoft/yii2-elasticsearch": "*"
```

to the require section of your composer.json.


Using the Query
---------------

TBD

> **NOTE:** elasticsearch limits the number of records returned by any query to 10 records by default.
> If you expect to get more records you should specify limit explicitly in relation definition.
 * This is also important for relations that use [[via()]] so that if via records are limited to 10
 * the relations records can also not be more than 10.
 *


Using the ActiveRecord
----------------------

For general information on how to use yii's ActiveRecord please refer to the [guide](https://github.com/yiisoft/yii2/blob/master/docs/guide/active-record.md).

For defining an elasticsearch ActiveRecord class your record class needs to extend from `yii\elasticsearch\ActiveRecord` and
implement at least the `attributes()` method to define the attributes of the record.
The handling of primary keys is different in elasticsearch as the primary key (the `_id` field in elasticsearch terms)
is not part of the attributes by default. However it is possible to define a [path mapping](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/mapping-id-field.html)
for the `_id` field to be part of the attributes.
See [elasticsearch docs](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/mapping-id-field.html) on how to define it.
The `_id` field of a document/record can be accessed using [[ActiveRecord::getPrimaryKey()]] and [[ActiveRecord::setPrimaryKey()]].
When path mapping is defined, the attribute name can be defined using the [[primaryKey()]] method.

The following is an example model called `Customer`:

```php
class Customer extends \yii\elasticsearch\ActiveRecord
{
    /**
     * @return array the list of attributes for this record
     */
    public function attributes()
    {
        // path mapping for '_id' is setup to field 'id'
        return ['id', 'name', 'address', 'registration_date'];
    }

    /**
     * @return ActiveRelation defines a relation to the Order record (can be in other database, e.g. redis or sql)
     */
    public function getOrders()
    {
        return $this->hasMany(Order::className(), ['customer_id' => 'id'])->orderBy('id');
    }

    /**
     * Defines a scope that modifies the `$query` to return only active(status = 1) customers
     */
    public static function active($query)
    {
        $query->andWhere(['status' => 1]);
    }
}
```

You may override [[index()]] and [[type()]] to define the index and type this record represents.

The general usage of elasticsearch ActiveRecord is very similar to the database ActiveRecord as described in the
[guide](https://github.com/yiisoft/yii2/blob/master/docs/guide/active-record.md).
It supports the same interface and features except the following limitations and additions(*!*):

- As elasticsearch does not support SQL, the query API does not support `join()`, `groupBy()`, `having()` and `union()`.
  Sorting, limit, offset and conditional where are all supported.
- `from()` does not select the tables, but the [index](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/glossary.html#glossary-index)
  and [type](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/glossary.html#glossary-type) to query against.
- `select()` has been replaced with `fields()` which basically does the same but `fields` is more elasticsearch terminology.
  It defines the fields to retrieve from a document.
- `via`-relations can not be defined via a table as there are no tables in elasticsearch. You can only define relations via other records.
- As elasticsearch is not only a data storage but also a search engine there is of course support added for search your records.
  There are `query()`, `filter()` and `addFacets()` methods that allows to compose an elasticsearch query.
  See the usage example below on how they work and check out the [Query DSL](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl.html)
  on how to compose `query` and `filter` parts.
- It is also possible to define relations from elasticsearch ActiveRecords to normal ActiveRecord classes and vice versa.

> **NOTE:** elasticsearch limits the number of records returned by any query to 10 records by default.
> If you expect to get more records you should specify limit explicitly in query **and also** relation definition.
> This is also important for relations that use via() so that if via records are limited to 10
> the relations records can also not be more than 10.


Usage example:

```php
$customer = new Customer();
$customer->primaryKey = 1; // in this case equivalent to $customer->id = 1;
$customer->attributes = ['name' => 'test'];
$customer->save();

$customer = Customer::get(1); // get a record by pk
$customers = Customer::mget([1,2,3]); // get multiple records by pk
$customer = Customer::find()->where(['name' => 'test'])->one(); // find by query
$customers = Customer::find()->active()->all(); // find all by query (using the `active` scope)

// http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-field-query.html
$result = Article::find()->query(["field" => ["title" => "yii"]])->all(); // articles whose title contains "yii"

// http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-flt-query.html
$query = Article::find()->query([
	"fuzzy_like_this" => [
		"fields" => ["title", "description"],
		"like_text" => "This query will return articles that are similar to this text :-)",
        "max_query_terms" : 12
	]
]);

$query->all(); // gives you all the documents
// you can add facets to your search:
$query->addStatisticalFacet('click_stats', ['field' => 'visit_count']);
$query->search(); // gives you all the records + stats about the visit_count field. e.g. mean, sum, min, max etc...
```

And there is so much more in it. "it’s endless what you can build"[¹](http://www.elasticsearch.org/)


Using the elasticsearch DebugPanel
----------------------------------

The yii2 elasticsearch extensions provides a `DebugPanel` that can be integrated with the yii debug module
and shows the executed elasticsearch queries. It also allows to run these queries
and view the results.

Add the following to you application config to enable it (if you already have the debug module
enabled, it is sufficient to just add the panels configuration):

```php
	// ...
	'preload' => 'debug',
	'modules' => [
		'debug' => [
			'class' => 'yii\\debug\\Module',
			'panels' => [
				'elasticsearch' => [
					'class' => 'yii\\elasticsearch\\DebugPanel',
				],
			],
		],
	],
	// ...
```

![elasticsearch DebugPanel](README-debug.png)


Relation definitions with records whose primary keys are not part of attributes
-------------------------------------------------------------------------------

TODO


Patterns
--------

### Fetching records from different indexes/types

TODO
