Trait reql::commands::Filter [−] [src]

pub trait Filter {
    fn filter<T>(&self, args: T) -> Command where T: ToArg;
}

Return all the elements in a sequence for which the given predicate is true

The return value of filter will be the same as the input (sequence, stream, or array). Documents can be filtered in a variety of ways—ranges, nested values, boolean conditions, and the results of anonymous functions.

By default, filter will silently skip documents with missing fields: if the predicate tries to access a field that doesn’t exist (for instance, the predicate {age: 30} applied to a document with no age field), that document will not be returned in the result set, and no error will be generated. This behavior can be changed with the default optional argument.

  • If default is set to true, documents with missing fields will be returned rather than skipped.
  • If default is set to r.error(), a RuntimeError will be thrown when a document with a missing field is tested.
  • If default is set to false (the default), documents with missing fields will be skipped.

Note: filter does not use secondary indexes. For retrieving documents via secondary indexes, consider get_all, between and eq_join.

Basic predicates

Example

Get all users who are 30 years old.

r.table("users").filter(args!({age: 30}));

The predicate {age: 30} selects documents in the users table with an age field whose value is 30. Documents with an age field set to any other value or with no age field present are skipped.

While the {field: value} style of predicate is useful for exact matches, a more general way to write a predicate is to use a Rust closure that returns true or false.

r.table("users").filter(args!(|user| user.get_field("age").eq(30)));

In this case, the function returns true if the field age is equal to 30. Predicates to filter are evaluated on the server, and must use ReQL expressions. Also, predicates must evaluate document fields. They cannot evaluate secondary indexes.

Example

Get all users who are more than 18 years old.

r.table("users").filter(args!(|user| user.get_field("age").gt(18)));

Example

Get all users who are less than 18 years old and more than 13 years old.

r.table("users").filter(args!(|user| {
    let age = user.get_field("age");
    age.lt(18).and(age.gt(13))
}));

Required Methods

Implementors