Function library

We list here the functions supported by Sparksoniq, and introduce them by means of examples. Highly detailed specifications can be found in the underlying W3C standard, unless the function is marked as specific to JSON or Sparksoniq.

Aggregation functions

sum

let $x := (1, 2, 3, 4)
return sum($x)

returns 10

count

let $x := (1, 2, 3, 4)
return count($x)

returns 4

min

let $x := (1, 2, 3, 4)
return min($x)

returns 1

max

let $x := (1, 2, 3, 4)
return max($x)

returns 4

avg

let $x := (1, 2, 3, 4)
return avg($x)

returns 2.5

Mathematic functions

abs

abs(-2)

returns 2.0

acos

asin

atan

atan2

ceiling

ceiling(2.3)

returns 3.0

cos

exp

exp10

floor

floor(2.3)

returns 2.0

log

log10

pow

pow(10, 2)

returns 100.0

round

round(2.3)

returns 2.0

round(2.2345, 2)

returns 2.23

round-half-to-even

sin

tan

String functions

concat

concat("foo", "bar", "foobar")

returns "foobarfoobar"

string-join

string-join(("foo", "bar", "foobar"))

returns "foobarfoobar"

string-join(("foo", "bar", "foobar"), "-")

returns "foo-bar-foobar"

substring

substring("foobar", 4)

returns "bar"

substring("foobar", 4, 2)

returns "ba"

Integration with HDFS and Spark

We support two more functions to read a JSON file from HDFS or send a large sequence to the cluster:

json-file (Sparksoniq specific)

Exists in unary and binary. The first parameter specifies the JSON file (or set of JSON files) to read. The second, optional parameter specifies the number of partitions. This is also similar to Sparks textFile().

Example of usage:

for $my-json in json-file("hdfs://host:port/directory/file.json")
where $my-json.property eq "some value"
return $my-json

If a host and port are set:

for $my-json in json-file("/absolute/directory/file.json")
where $my-json.property eq "some value"
return $my-json

For a set of files:

for $my-json in json-file("/absolute/directory/file-*.json")
where $my-json.property eq "some value"
return $my-json

If a working directory is set:

for $my-json in json-file("file.json")
where $my-json.property eq "some value"
return $my-json

parallelize (Sparksoniq specific)

This function behaves like the Spark parallelize() you are familiar with and sends a large sequence to the cluster. The rest of the FLWOR expression is then evaluated with Spark transformations on the cluster.

for $i in parallelize(1 to 1000000)
where $i mod 1000 eq 0
return $i

In the future, it will also have a second, optional parameter that specifies the number of partitions.

for $i in parallelize(1 to 1000000, 100)
where $i mod 1000 eq 0
return $i