ReQL Functions

Functions may be used to enhance your ReQL queries – for example up-sell or getting nearby items can be achieved easily by functions.

There are various functions like math functions (rounding, computing square root …), string functions (converting case), function for getting size of set or string, getting current timestamp, functions for conversions between types (for example conversion between date in a text representation and timestamp) or even lambda functions. If you are missing some function that you would like to use, please let us know.

ReQL function can take arguments and returns a single value. Arguments are placed between parentheses and are separated by commas – for example computing base 2 logarithm of 8 looks like this: log(8,2). If the function takes no arguments the parentheses may be omitted (for e.g. now). If the function is given wrong number of arguments, or the arguments have unsupported type, an error is produced. If any of the arguments is null, then result is also a null value.

Quick Overview

Context

Name	Description	Example
context_item	Retrieves property value of the item, that is currently viewed by the user.	`context_item["price"]`
context_user	Retrieves property value of the user, that is about to obtain the recommendations.	`context_user["country"]`
context_segment	Retrieves the Segment on which the recommendations are based	`context_segment["segmentId"]`

Miscellaneous

Name	Description	Example
now	Returns current timestamp	`now() > timestamp("2015-06-24T17:35:50Z")`
random	Returns a random number between 0 and 1	`1>=random()>=0`
size	Returns the length of a string or number of objects in a set	`size("Recombee") == 8`
item_values	Returns property values of a particular item as a dictionary	`item_values("item-42")["description"]`
reduce	Reduces a set into a single value using an operator	`reduce("+", {1, 2, 3}) == 6`

Lambda

Name	Description	Example
map	Applies the lambda expression to every member of a set	`map(lambda 'x': 2*'x', {1, 2, 3}) == {2, 4, 6}`
select	Returns only those values of input set for which the lambda expression returns true	`select(lambda 'x': 'x' > 5, {10, 2, 13, 1}) == {10, 13}`
exists	Returns true if lambda expression is satisfied for at least one element of the input set	`exists(lambda 'x': 'x' > 5, {2, 13, 4})`

Type Conversion

Name	Description	Example
boolean	Converts the argument to boolean	`boolean("") == False`
number	Converts the argument to number	`number("456") == 456`
string	Converts the argument to string	`string(123) == "123"`
timestamp	Converts the argument to timestamp	`timestamp("2015-06-25T11:08:44Z") == timestamp(1435230524)`

Math

Name	Description	Example
max	Returns the maximum of n arguments	`max(147,42,81.9) == 147`
min	Returns the minimum of n arguments	`min(147,42,81.9) == 42`
avg	Returns the average of n numbers	`avg(2, 4) == 3`
round	Returns closest integer	`round(4.5) == 5`
floor	Returns largest preceding integer	`floor(4.3) == 4`
ceil	Returns smallest following integer	`ceil(4.3) == 5`
abs	Returns non-negative value of the argument without regard to its sign	`abs(-4.3) == 4.3`
sqrt	Returns the square root of the argument	`sqrt(4) == 2`
pow	Returns 𝑓𝑖𝑟𝑠𝑡_𝑎𝑟𝑔𝑢𝑚𝑒𝑛𝑡^{𝑠𝑒𝑐𝑜𝑛𝑑_𝑎𝑟𝑔𝑢𝑚𝑒𝑛𝑡}	`pow(10,3) == 1000`
log	Returns the logarithm of the argument	`log(1000) == 3`

String

Name	Description	Example
upper	Converts all letters to the capital letters	`upper("AbCdefG") == "ABCDEFG"`
lower	Converts all letters to the small letters	`lower("AbCdefG") == "abcdefg"`
split	Splits a string into sub-strings using a separator	`split("abc,def,ghi", ",") == ["abc", "def", "ghi"]`

Interactions Listing

Name	Description	Example
user_interactions	Returns list of interactions by a particular user	`user_interactions(context_user["userId"], {"purchases"})`

Interactions Statistics

Name	Description	Example
num_item_bookmarks	Returns the number of bookmarks of an item	`num_item_bookmarks('itemId') < 10`
num_item_detail_views	Returns the number of detail views of an item	`num_item_detail_views('itemId') < 10`
num_item_purchases	Returns the number of purchases of an item	`num_item_purchases('itemId') < 10`
num_item_ratings	Returns the number of ratings of an item	`num_item_ratings('itemId', "negative") < 10`

Item Segments Handling

Name	Description	Example
segment_items	Get items in a Segment	`'itemId' in segment_items("genres", "thriller")`
item_segments	Get Item Segments to which the item belongs	`"thriller" in item_segments("genres", 'itemId')`

Geographical

Name	Description	Example
earth_distance	Returns the orthodromic distance between two points (given as their latitude and longitude in degrees) in meters	`earth_distance(50.075538,14.437800,52.520007,13.404954) < 282000`
geo_polygon	Creates a spherical polygon represented by points with geographical coordinates	`geo_polygon([[40.800, -73.957], [40.767, -73.981], [40.764, -73.972], [40.796, -73.949]])`
geo_radius	Creates a spherical cap represented by a center with geographical coordinates and a radius in km	`geo_radius([40.689167, -74.044444], 10)`

docs.recombee.com