Queries Edit on GitHub

Resource collections exposed from an IQueryable<T> source can be queried using the a standard set of query parameters.

Query parameters

$filter: predicate expression
$groupby: group by expression
$select: selector expression(s)
$orderby: ordering expression(s)
$skip: number of items to skip
$take: number of items to return
$projection: projection, can be one of the following
$expand: property paths to expand

$filter

The $filter query parameter can be used to filter the results. The filter is applied before groupby and $select.

$ curl 'http://localhost:1337/game-consoles?$filter=name%20eq%20%27Game%20Boy%27' -H "Accept: application/json"
{
  "_type": "__result__",
  "totalCount": -1,
  "items": [
    {
      "_uri": "http://localhost:1337/game-consoles/gameboy",
      "id": "gameboy",
      "name": "Game Boy"
    }
  ],
  "skip": 0,
  "previous": null,
  "next": null
}

$select

The $select query parameter can be used for limiting the amount of data to retrieve, or for applying simple transformations.

It accepts a comma separated list of expressions and names, of the pattern

expr1 as name1,expr2 as name2

The as name part is optional if the expression is a simple property reference, in which case the expression property name will be used as the name.

The results will take the form of JSON objects with properties corresponding to the list of expressions in $select.

$ curl 'http://localhost:1337/game-consoles?$select=id,toupper(name)%20as%20n' -H "Accept: application/json"
{
  "_type": "__result__",
  "totalCount": -1,
  "items": [
    {
      "id": "gameboy",
      "n": "GAME BOY"
    },
    {
      "id": "nes",
      "n": "NINTENDO ENTERTAINMENT SYSTEM"
    }
  ],
  "skip": 0,
  "previous": null,
  "next": null
}

When selecting just one value we can avoid wrapping it in an object by using the special form expr as this.

$ curl 'http://localhost:1337/game-consoles?$select=toupper(name)%20as%20this' -H "Accept: application/json"
{
  "_type": "__result__",
  "totalCount": -1,
  "items": [
    "ATARI 2600",
    "GAME BOY",
    "NINTENDO ENTERTAINMENT SYSTEM"
  ],
  "skip": 0,
  "previous": null,
  "next": null
}

$projection

The $projection query parameter controls what projection will be applied to the query results.

first: First resource of result set, 404 if not found
first: Last resource of result set, 404 if not found
single: First and only resource of result set. 404 if not found, 400 if several found
firstordefault: First resource of result set, null
lastordefault: First resource of result set, null
max: Max value (only valid when $select expression returns a comparable value)
min: Min value (only valid when $select expression returns a comparable value)
count: Number of results
sum: Sum of results (only valid when $select expression returns a summable value)

Operators

Boolean

and, &&: And (conditional)
or, ||: Or (conditional)

Multiplicative

mul, *: Multiply
div, /: Divide
mod, %: Modulus

Additive

add, +: Add
sub, -: Subtract

Relational

eq, ==: Equals
ne, !=: Not equals
gt, >: Greater than
lt, <: Less than
ge, >=: Greater than or equal
le, <=: Less than or equal

Grammar

For the complete grammar look at the ANTLR3 grammar file PomonaQuery.q.

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