Presto User-Defined Functions(UDFs)

Plugin for Presto to allow addition of user defined functions. The plugin simplifies the process of adding user functions to Presto.

Plugging in Presto UDFs

The details about how to plug in presto UDFs can be found here.

Presto Version Compatibility

Presto Version	Last Compatible Release
ver 0.180	current
ver 0.157	udfs-2.0.1
ver 0.142	udfs-1.0.0
ver 0.119	udfs-0.1.3

Implemented User Defined Functions

The repository contains the following UDFs implemented for Presto :

HIVE UDFs

• DATE-TIME Functions

1. to_utc_timestamp(timestamp, string timezone) -> timestamp
   Assumes given timestamp is in given timezone and converts to UTC (as of Hive 0.8.0). For example, to_utc_timestamp('1970-01-01 00:00:00','PST') returns 1970-01-01 08:00:00.
2. from_utc_timestamp(timestamp, string timezone) -> timestamp
   Assumes given timestamp is UTC and converts to given timezone (as of Hive 0.8.0). For example, from_utc_timestamp('1970-01-01 08:00:00','PST') returns 1970-01-01 00:00:00.
3. unix_timestamp() -> timestamp
   Gets current Unix timestamp in seconds.
4. year(string date) -> int
   Returns the year part of a date or a timestamp string: year("1970-01-01 00:00:00") = 1970, year("1970-01-01") = 1970.
5. month(string date) -> int
   Returns the month part of a date or a timestamp string: month("1970-11-01 00:00:00") = 11, month("1970-11-01") = 11.
6. day(string date) -> int
   Returns the day part of a date or a timestamp string: day("1970-11-01 00:00:00") = 1, day("1970-11-01") = 1.
7. hour(string date) -> int
   Returns the hour of the timestamp: hour('2009-07-30 12:58:59') = 12, hour('12:58:59') = 12.
8. minute(string date) -> int
   Returns the minute of the timestamp: minute('2009-07-30 12:58:59') = 58, minute('12:58:59') = 58.
9. second(string date) -> int
   Returns the second of the timestamp: second('2009-07-30 12:58:59') = 59, second('12:58:59') = 59.
10. to_date(string timestamp) -> string
    Returns the date part of a timestamp string: to_date("1970-01-01 00:00:00") = "1970-01-01"
11. weekofyear(string date) -> int
    Returns the week number of a timestamp string: weekofyear("1970-11-01 00:00:00") = 44, weekofyear("1970-11-01") = 44.
12. date_sub(string startdate, int days) -> string
    Subtracts a number of days to startdate: date_sub('2008-12-31', 1) = '2008-12-30'.
13. date_add(string startdate, int days) -> string
    Adds a number of days to startdate: date_add('2008-12-31', 1) = '2009-01-01'.
14. datediff(string enddate, string startdate) -> string
    Returns the number of days from startdate to enddate: datediff('2009-03-01', '2009-02-27') = 2.
15. format_unixtimestamp(bigint unixtime[, string format]) -> string
    Converts the number of seconds from unix epoch (1970-01-01 00:00:00 UTC) to a string representing the timestamp of that moment in the current system time zone in the format of "1970-01-01 00:00:00" unless a format string is specified. If a format string is specified the epoch time is converted in the specified format. More information about the formatter can be found here.
    NOTE : Due to name collision of presto 0.142's implementaion of from_unixtime(bigint unixtime) function, which returns the value as a timestamp type and Hive's from_unixtime(bigint unixtime[, string format]) function, which returns the value as string type and supports formatter, the hive UDF has been implemented as format_unixtimestamp(bigint unixtime[, string format]).

• MATH Functions

1. pmod(INT a, INT b) -> INT, pmod(DOUBLE a, DOUBLE b) -> DOUBLE
   Returns the positive value of a mod b: pmod(17, -5) = -3.
2. rands(INT seed) -> DOUBLE
   Returns a random number (that changes from row to row) that is distributed uniformly from 0 to 1. Specifying the seed will make sure the generated random number sequence is deterministic: rands(3) = 0.731057369148862
   NOTE : Due to name collision of presto 0.142's implementaion of rand(int a) function, which returns a number between 0 to a and Hive's rand(int seed) function, which sets the seed for the random number generator, the hive UDF has been implemented as rands(int seed).
3. bin(BIGINT a) -> STRING
   Returns the number in binary format: bin(100) = 1100100.
4. hex(BIGINT a) -> STRING, hex(STRING a) -> STRING, hex(BINARY a) -> STRING
   If the argument is an INT or binary, hex returns the number as a STRING in hexadecimal format. Otherwise if the number is a STRING, it converts each character into its hexadecimal representation and returns the resulting STRING: hex(123) = 7b, hex('123') = 7b, hex('1100100') = 64.
5. unhex(STRING a) -> BINARY
   Inverse of hex. Interprets each pair of characters as a hexadecimal number and converts to the byte representation of the number: unhex('7b') = 1111011.

• STRING Functions

1. locate(string substr, string str[, int pos]) -> int
   Returns the position of the first occurrence of substr in str after position pos: locate('si', 'mississipi', 2) = 4, locate('si', 'mississipi', 5) = 7
2. find_in_set(string str, string strList) -> int
   Returns the first occurance of str in strList where strList is a comma-delimited string. Returns null if either argument is null. Returns 0 if the first argument contains any commas: find_in_set('ab', 'abc,b,ab,c,def') returns 3.
3. instr(string str, string substr) -> int
   Returns the position of the first occurrence of substr in str. Returns null if either of the arguments are null and returns 0 if substr could not be found in str: instr('mississipi' , 'si') = 4.

• CONDITIONAL Functions

  1. nvl(T value, T default_value) -> T
     ** Supported only till v1.0.0 due to the limitations presto new versions of Presto puts on plugins Returns default value if value is null else returns value: nvl(3,4) = 3, nvl(NULL,4) = 4.

• MISCELLANEOUS Functions

  1. hash(a1[, a2...]) -> int
     ** Supported only till v1.0.0 due to the limitations presto new versions of Presto puts on plugins Returns a hash value of the arguments. hash('a','b','c') = 143025634.

Adding User Defined Functions to Presto-UDFs

Functions can be added using annotations, follow https://prestodb.io/docs/0.157/develop/functions.html for details on how to add functions

** Note that Code generated functions were supported only till v1.0.0 due to the limitations presto new versions of Presto puts on plugins

Release a new version of presto-udfs

Releases are always created from master. During development, master has a version like X.Y.Z-SNAPSHOT.

# Change version as per http://semver.org/
mvn release:prepare -Prelease
mvn release:perform -Prelease
git push
git push --tags