== Search Operations

Well...it isn't called elasticsearch for nothing!  Let's talk about search operations in the client.

The client gives you full access to every query and parameter exposed by the REST API, following the naming scheme as
much as possible. Let's look at a few examples so you can become familiar with the syntax.

=== Match Query

Here is a standard curl for a Match query:

[source,shell]
----
curl -XGET 'localhost:9200/my_index/my_type/_search' -d '{
    "query" : {
        "match" : {
            "testField" : "abc"
        }
    }
}'
----
{zwsp} +

And here is the same query constructed in the client:

[source,php]
----
$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'match' => [
                'testField' => 'abc'
            ]
        ]
    ]
];

$results = $client->search($params);
----
{zwsp} +

Notice how the structure and layout of the PHP array is identical to that of the JSON request body.  This makes it very
simple to convert JSON examples into PHP.  A quick method to check your PHP array (for more complex examples) is to
encode it back to JSON and check by eye:

[source,php]
----
$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'match' => [
                'testField' => 'abc'
            ]
        ]
    ]
];

print_r(json_encode($params['body']));


{"query":{"match":{"testField":"abc"}}}
----
{zwsp} +


.Using Raw JSON
****
Sometimes it is convenient to use raw JSON for testing purposes, or when migrating from a different system.  You can
use raw JSON as a string in the body, and the client will detect this automatically:

[source,php]
----
$json = '{
    "query" : {
        "match" : {
            "testField" : "abc"
        }
    }
}';

$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => $json
];

$results = $client->search($params);
----
****
{zwsp} +

Search results follow the same format as Elasticsearch search response, the only difference is that the JSON response is
serialized back into PHP arrays. Working with the search results is as simple as iterating over the array values:

[source,php]
----
$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'match' => [
                'testField' => 'abc'
            ]
        ]
    ]
];

$results = $client->search($params);

$milliseconds = $results['took'];
$maxScore     = $results['hits']['max_score'];

$score = $results['hits']['hits'][0]['_score'];
$doc   = $results['hits']['hits'][0]['_source'];
----
{zwsp} +

=== Bool Queries

Bool queries can be easily constructed using the client. For example, this query:
[source,shell]
----
curl -XGET 'localhost:9200/my_index/my_type/_search' -d '{
    "query" : {
        "bool" : {
            "must": [
                {
                    "match" : { "testField" : "abc" }
                },
                {
                    "match" : { "testField2" : "xyz" }
                }
            ]
        }
    }
}'
----
{zwsp} +

Would be structured like this (Note the position of the square brackets):
[source,php]
----
$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'bool' => [
                'must' => [
                    [ 'match' => [ 'testField' => 'abc' ] ],
                    [ 'match' => [ 'testField2' => 'xyz' ] ],
                ]
            ]
        ]
    ]
];

$results = $client->search($params);
----
{zwsp} +

Notice that the `must` clause accepts an array of arrays.  This will be serialized into an array of JSON objects internally,
so the final resulting output will be identical to the curl example.  For more details about arrays vs objects in PHP,
see <<php_json_objects, Dealing with JSON Arrays and Objects in PHP>>.

=== A more complicated example

Let's construct a slightly more complicated example: a boolean query that contains both a filter and a query.
This is a very common activity in elasticsearch queries, so it will be a good demonstration.

The curl version of the query:

[source,shell]
----
curl -XGET 'localhost:9200/my_index/my_type/_search' -d '{
    "query" : {
        "bool" : {
            "filter" : {
                "term" : { "my_field" : "abc" }
            },
            "should" : {
                "match" : { "my_other_field" : "xyz" }
            }
        }
    }
}'
----
{zwsp} +

And in PHP:

[source,php]
----
$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'bool' => [
                'filter' => [
                    'term' => [ 'my_field' => 'abc' ]
                ],
                'should' => [
                    'match' => [ 'my_other_field' => 'xyz' ]
                ]
            ]
        ]
    ]
];


$results = $client->search($params);
----
{zwsp} +


=== Scrolling

The Scrolling functionality of Elasticsearch is used to paginate over many documents in a bulk manner, such as exporting
all the documents belonging to a single user.  It is more efficient than regular search because it doesn't need to maintain
an expensive priority queue ordering the documents.

Scrolling works by maintaining a "point in time" snapshot of the index which is then used to page over.
This window allows consistent paging even if there is background indexing/updating/deleting.  First, you execute a search
request with `scroll` enabled.  This returns a "page" of documents, and a scroll_id which is used to continue
paginating through the hits.

More details about scrolling can be found in the https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-scroll.html[Link: reference documentation].

This is an example which can be used as a template for more advanced operations:

[source,php]
----
$client = ClientBuilder::create()->build();
$params = [
    "scroll" => "30s",          // how long between scroll requests. should be small!
    "size" => 50,               // how many results *per shard* you want back
    "index" => "my_index",
    "body" => [
        "query" => [
            "match_all" => new \stdClass() 
        ]
    ]
];

// Execute the search
// The response will contain the first batch of documents
// and a scroll_id
$response = $client->search($params);

// Now we loop until the scroll "cursors" are exhausted
while (isset($response['hits']['hits']) && count($response['hits']['hits']) > 0) {

    // **
    // Do your work here, on the $response['hits']['hits'] array
    // **

    // When done, get the new scroll_id
    // You must always refresh your _scroll_id!  It can change sometimes
    $scroll_id = $response['_scroll_id'];

    // Execute a Scroll request and repeat
    $response = $client->scroll([
            "scroll_id" => $scroll_id,  //...using our previously obtained _scroll_id
            "scroll" => "30s"           // and the same timeout window
        ]
    );
}
----
