@travetto/model-query-language/README.md

Datastore query language.

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# Data Model Query Language

## Datastore query language.

**Install: @travetto/model-query-language**
```bash
npm install @travetto/model-query-language

# or

yarn add @travetto/model-query-language
```

This module provides a textual query language for the [Data Model Querying](https://github.com/travetto/travetto/tree/main/module/model-query#readme "Datastore abstraction for advanced query support.") interface. The language itself is fairly simple, boolean logic, with parenthetical support.The operators supported are:

## Query Language

   *  `<`, `<=` - Less than, and less than or equal to
   *  `>`, `>=` - Greater than, and greater than or equal to
   *  `!=`, `==` - Not equal to, and equal to
   *  `~` - Matches regular expression, supports the `i` flag to trigger case insensitive searches
   *  `!`, `not` - Negates a clause
   *  `in`, `not-in` - Supports checking if a field is in a list of literal values
   *  `and`, `&&` - Intersection of clauses
   *  `or`, `||` - Union of clauses

All sub fields are dot separated for access, e.g. `user.address.city`.A query language version of the previous query could look like:

**Code: Query language with boolean checks and exists check**
```sql
not (age < 35) and contact != null
```

A more complex query would look like:

**Code: Query language with more complex needs**
```sql
user.role in ['admin', 'root'] && (user.address.state == 'VA' || user.address.city == 'Springfield')
```

### Regular Expression
When querying with regular expressions, patterns can be specified as `'strings'` or as `/patterns/`.  The latter allows for the case insensitive modifier: `/pattern/i`.  Supporting the insensitive flag is up to the underlying model implementation.