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advanced-queries.md

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Advanced queries

ElasticVision expands your possibilities using query builders to write more complex queries. First there are the three methods to set the context of the query: must, should and filter.

From the Elasticsearch documentation:

must: The query must appear in matching documents and will contribute to the score.

should: The query should appear in the matching document.

filter: The query must appear in matching documents. However unlike must the score of the query will be ignored.

Together they take in ElasticVision a more-matches-is-better approach, the more a document matches with the given queries, the higher its score. The filter context is best used for structured data, such as dates or flags.

In ElasticVision, you can build a compound query as complex as you like. Elasticsearch provides a broad set of queries, these are the query types implementing SyntaxInterface. There is for example the MultiMatch for fuzzy search and Term for a very precise search. It is too much to list every type of query here. At the time of writing, ElasticVision does not yet have every Elasticsearch query type that is out there. It is however very easy to write a class for a missing query type, and if you do write one a Pull Request is more than welcome!

Fuzziness

The Matching and MultiMatch queries accept a fuzziness parameter. By default, it is set to 'auto' but the Elasticsearch docs explain in depth which other values you could use.

"When querying text or keyword fields, fuzziness is interpreted as a Levenshtein Edit Distance - the number of one character changes that need to be made to one string to make it the same as another string."

Retrieving selected fields

By default ElasticVision will retrieve all fields for the documents that get returned. You can change this by using the field() function on the search query builder. It is important to know that this does necessarily have a performance improvement, the whole document is still being processed by Elasticsearch.

"By default, each hit in the search response includes the document _source, which is the entire JSON object that was provided when indexing the document. To retrieve specific fields in the search response, you can use the fields parameter" (source)

use App\Models\Post;

$results = Post::search('Self-steering')
    ->field('id')
    ->field('published_at')
    ->get();

Query properties

Elastic has a multitude of options one can add to its queries.

In Explorer one can easily add these with Query Properties, you can create a class , implement the QueryProperty interface and pass it to the query. An example of this is source field filtering which we included in the SourceFilter class.

use App\Models\Post;
use Hilsonxhero\ElasticVision\Domain\Query\QueryProperties\SourceFilter;

$results = Post::search('Self-steering')
    ->field('id')
    ->property(SourceFilter::empty()->include('*.description')->exclude('*_secret'))
    ->get();