Shapes

Subtopics

A computed field in a shape gets calculated for every object on which it is defined, not just the ones that make it through the filter, but every one. The filter may, in fact, refer to a computed value, so it must be known for all objects. This may be inefficient in some cases, such as the previous example with fetching the posts with their length and a comparison to average post length. You can use a with block to factor out some common computations, give them names and use them later on in a query. Let's re-write our inefficient query like this:

Input

Run

with
  # No longer need a detached here, because Account is
  # already in a different scope from the query below.
  avg_len := math::mean(len(detached Account.username))
select Account {
  username,
  len_username := len(.username),
  above_avg := len(.username) > avg_len
};

with
  # No longer need a detached here, because Account is
  # already in a different scope from the query below.
  avg_len := math::mean(len(detached Account.username))
select Account {
  username,
  len_username := len(.username),
  above_avg := len(.username) > avg_len
};

Output Objects

Press the 'Run' button to evaluate the input

The with block is also very convenient if you need to compare objects in a set to other objects in the same set, such as "find all movies that have the same title". The with block makes it easy to define a copy of the original set to be used later in comparisons. Try this out:

Input

Run

with
  # Define a set M, identical to Movie
  M := Movie
select Movie {
  title,
  release_year
} filter .title = M.title
  and
  # This is to make sure that we've matched the title
  # on a different post.
  Movie != M;

with
  # Define a set M, identical to Movie
  M := Movie
select Movie {
  title,
  release_year
} filter .title = M.title
  and
  # This is to make sure that we've matched the title
  # on a different post.
  Movie != M;

Output Objects

Press the 'Run' button to evaluate the input

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