Count function

This function can be used when counting field values and expressions.

count

The count function counts the number of times that the function is called. This is useful for returning the total number of rows in a SELECT statement with a GROUP BY clause.

count() -> 1

If a value is given as the first argument, then this function checks whether a given value is truthy. This is useful for returning the total number of rows, which match a certain condition, in a SELECT statement, with a GROUP BY clause.

count(any) -> number

If an array is given, this function counts the number of items in the array which are truthy. If, instead, you want to count the total number of items in the given array, then use the array::len() function.

count(array) -> number

The following example shows this function, and its output, when used in a RETURN statement:

RETURN count();

-- 1

RETURN count(true);

-- 1

RETURN count(10 > 15);

-- 0

RETURN count([ 1, 2, 3, null, 0, false, (15 > 10), rand::uuid() ]);

5

The following examples show this function being used in a SELECT statement with a GROUP clause:

SELECT 
	count() 
FROM [
	{ age: 33 }, 
	{ age: 45 }, 
	{ age: 39 }
] 
GROUP ALL;

[
	{ count: 3 }
]

SELECT 
	count(age > 35) 
FROM [
	{ age: 33 }, 
	{ age: 45 }, 
	{ age: 39 }
] 
GROUP ALL;

[
	{ count: 2 }
]

An advanced example of the count function can be seen below:

SELECT
	country,
	count(age > 30) AS total
FROM [
	{ age: 33, country: 'GBR' },
	{ age: 45, country: 'GBR' },
	{ age: 39, country: 'USA' },
	{ age: 29, country: 'GBR' },
	{ age: 43, country: 'USA' }
]
GROUP BY country;

[
	{
		country: 'GBR',
		total: 2
	},
	{
		country: 'USA',
		total: 2
	}
]

Using a COUNT index with count()

A COUNT index can be defined to speed up count() when used with a GROUP ALL clause. This allows count() to access a single stored value when it is called instead of iterating over the entire table.

CREATE user;
-- One record in table, very fast
SELECT count() FROM user GROUP ALL;

-- 10,000 new records,
-- count() takes a bit longer than before
CREATE |user:10000| RETURN NONE;
SELECT count() FROM user GROUP ALL;

-- Add index, wait a moment for it to build
DEFINE INDEX user_count ON user COUNT;
-- count() very performant again
SELECT count() FROM user GROUP ALL;