Explain Query Language#

The idea of Search-a-licious is to provide a powerfull yet easy to use API, through the use of a well proven language: Lucene Query Language.

While Elasticsearch provides a way to use this language in the queries, it has some important limitations like the lack of support for nested and object fields.

Thanks to the luqum library, Search-a-licious is able to use Lucene Query Language in a broader way.

Search-a-licious also use luqum to introspect the query and transform it to add features corresponding to your configuration and leverage taxonomies and other peculiarities.

It enables for example taking into account synonyms, or adding the languages to query about on the fly without the need to complexify the query to much at API level.

Query syntax#

The query syntax is quite simple, you can either:

query for simple word in the default texts fields (those having full_text_search property in your configuration) by simply having the word in your query:
```
chocolate
```
Entries with text chocolate
or match exactly a full sentences by using quotes:
```
"dark chocolate"
```
Entries with text dark chocolate
you can also match a word or phrase in a specific field by using the field name, followed by a colon:
```
labels:organic
```
Entries with labels containing organic
you can have more than one term, the query will try to match all terms:
```
"dark chocolate" labels:organic
```
Entries with text dark chocolate and labels containing organic
you can combine queries with AND, OR and NOT operators, and use parenthesis to group them:
```
"dark chocolate AND (labels:organic OR labels:vegan) AND NOT nutriscore:(e OR d)"
```
Entries with text dark chocolate, labels containing organic or vegan, and Nutri-Score not e or d
you can query a sub field by using "." or ":":
```
nutrients.sugar_100g:[10 TO 15]
```
equivalent to:
```
nutrients:sugar_100g:[10 TO 15]
```
Entries with sugar between 10 and 15 grams per 100g
in range you can use * for unbounded values:
```
nutrients.sugar_100g:[* TO 20] AND nutrients.proteins_100g:[2 TO *]
```
Entries with sugar below 20 g and proteins above 2g for 100g
match field existence with *:
```
nutriscore:*
```
Entries with Nutri-Score computed

Different type of fields#

When you created you configuration, you defined different fields types. It's important because the matching possibilities are not the same.

In particular for text entries, there are two types of fields:

keyword fields, that are used for exact matching
full text fields, where part of the text can be matched, with complex matching possibilities

There are also numeric and date fields, that can be used for range matching, or to make computations.

Full text queries#

FIXME add more on how we transform queries