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Hive Function Cheat Sheet

Hive Function Meta commands

  • SHOW FUNCTIONS– lists Hive functions and operators
  • DESCRIBE FUNCTION [function name]– displays short description of the function
  • DESCRIBE FUNCTION EXTENDED [function name]– access extended description of the function

Types of Hive Functions

  • UDF– is a function that takes one or more columns from a row as argument and returns a single value or object. Eg: concat(col1, col2)
  • UDTF— takes zero or more inputs and and produces multiple columns or rows of output. Eg: explode()
  • Macros— a function that uses other Hive functions.

How To Develop UDFs

package org.apache.hadoop.hive.contrib.udf.example;

import java.util.Date;
import java.text.SimpleDateFormat;
import org.apache.hadoop.hive.ql.exec.UDF;

@Description(name = "YourUDFName",
    value = "_FUNC_(InputDataType) - using the input datatype X argument, "+
            "returns YYY.",
    extended = "Example:\n"
             + "  > SELECT _FUNC_(InputDataType) FROM tablename;")

public class YourUDFName extends UDF{
..
  public YourUDFName( InputDataType InputValue ){
    ..;
  }

  public String evaluate( InputDataType InputValue ){
    ..;
  }
}

How To Develop UDFs, GenericUDFs, UDAFs, and UDTFs

  • public class YourUDFName extends UDF{
  • public class YourGenericUDFName extends GenericUDF {..}
  • public class YourGenericUDAFName extends AbstractGenericUDAFResolver {..}
  • public class YourGenericUDTFName extends GenericUDTF {..}

How To Deploy / Drop UDFs

At start of each session:

ADD JAR /full_path_to_jar/YourUDFName.jar;
    CREATE TEMPORARY FUNCTION YourUDFName AS 'org.apache.hadoop.hive.contrib.udf.example.YourUDFName';

At the end of each session:

DROP TEMPORARY FUNCTION IF EXISTS YourUDFName;

Date Functions

The following built-in date functions are supported in hive:

Return Type Name(Signature) Example
string from_unixtime(bigint unixtime[, string format]) 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”
bigint unix_timestamp() Gets current time stamp using the default time zone.
bigint unix_timestamp(string date) Converts time string in format yyyy-MM-dd HH:mm:ss to Unix time stamp, return 0 if fail: unix_timestamp(‘2009-03-20 11:30:01’) = 1237573801
bigint unix_timestamp(string date, string pattern) Convert time string with given pattern to Unix time stamp, return 0 if fail: unix_timestamp(‘2009-03-20’, ‘yyyy-MM-dd’) = 1237532400
string to_date(string timestamp) Returns the date part of a timestamp string: to_date(“1970-01-01 00:00:00”) = “1970-01-01”
int year(string date) Returns the year part of a date or a timestamp string: year(“1970-01-01 00:00:00”) = 1970, year(“1970-01-01”) = 1970
int month(string date) Returns the month part of a date or a timestamp string: month(“1970-11-01 00:00:00”) = 11, month(“1970-11-01”) = 11
int day(string date) dayofmonth(date) Return the day part of a date or a timestamp string: day(“1970-11-01 00:00:00”) = 1, day(“1970-11-01”) = 1
int hour(string date) Returns the hour of the timestamp: hour(‘2009-07-30 12:58:59′) = 12, hour(’12:58:59’) = 12
int minute(string date) Returns the minute of the timestamp
int second(string date) Returns the second of the timestamp
int weekofyear(string date) Return the week number of a timestamp string: weekofyear(“1970-11-01 00:00:00”) = 44, weekofyear(“1970-11-01”) = 44
int datediff(string enddate, string startdate) Return the number of days from startdate to enddate: datediff(‘2009-03-01’, ‘2009-02-27’) = 2
string date_add(string startdate, int days) Add a number of days to startdate: date_add(‘2008-12-31’, 1) = ‘2009-01-01’
string date_sub(string startdate, int days) Subtract a number of days to startdate: date_sub(‘2008-12-31’, 1) = ‘2008-12-30’
timestamp from_utc_timestamp(timestamp, string timezone) Assumes given timestamp ist UTC and converts to given timezone (as of Hive 0.8.0)
timestamp to_utc_timestamp(timestamp, string timezone) Assumes given timestamp is in given timezone and converts to UTC (as of Hive 0.8.0)

Mathematical Functions

The following built-in mathematical functions are supported in hive; most return NULL when the argument(s) are NULL:

Return Type Name(Signature) Example
BIGINT round(double a) Returns the rounded BIGINT value of the double
DOUBLE round(double a, int d) Returns the double rounded to d decimal places
BIGINT floor(double a) Returns the maximum BIGINT value that is equal or less than the double
BIGINT ceil(double a), ceiling(double a) Returns the minimum BIGINT value that is equal or greater than the double
double rand(), rand(int seed) Returns a random number (that changes from row to row) that is distributed uniformly from 0 to 1. Specifiying the seed will make sure the generated random number sequence is deterministic.
double exp(double a) Returns ea where e is the base of the natural logarithm
double ln(double a) Returns the natural logarithm of the argument
double log10(double a) Returns the base-10 logarithm of the argument
double log2(double a) Returns the base-2 logarithm of the argument
double log(double base, double a) Return the base “base” logarithm of the argument
double pow(double a, double p), power(double a, double p) Return ap
double sqrt(double a) Returns the square root of a
string bin(BIGINT a) Returns the number in binary format
string hex(BIGINT a) hex(string a) If the argument is an int, hex returns the number as a string in hex format. Otherwise if the number is a string, it converts each character into its hex representation and returns the resulting string.
string unhex(string a) Inverse of hex. Interprets each pair of characters as a hexidecimal number and converts to the character represented by the number.
string conv(BIGINT num, int from_base, int to_base), conv(STRING num, int from_base, int to_base) Converts a number from a given base to another
double abs(double a) Returns the absolute value
int double pmod(int a, int b) pmod(double a, double b) Returns the positive value of a mod b
double sin(double a) Returns the sine of a (a is in radians)
double asin(double a) Returns the arc sin of x if -1<=a<=1 or null otherwise
double cos(double a) Returns the cosine of a (a is in radians)
double acos(double a) Returns the arc cosine of x if -1<=a<=1 or null otherwise
tan(double a) tan(double a) Returns the tangent of a (a is in radians)
double atan(double a) Returns the arctangent of a
double degrees(double a) Converts value of a from radians to degrees
double radians(double a) Converts value of a from degrees to radians
int double positive(int a), positive(double a) Returns a
int double negative(int a), negative(double a) Returns -a
float sign(double a) Returns the sign of a as ‘1.0’ or ‘-1.0’
double e() Returns the value of e
double pi() Returns the value of pi

String Functions

The following are built-in String functions are supported in hive:

Return Type Name(Signature) Example
int ascii(string str) Returns the numeric value of the first character of str
string concat(string|binary A, string|binary B…) Returns the string or bytes resulting from concatenating the strings or bytes passed in as parameters in order. e.g. concat(‘foo’, ‘bar’) results in ‘foobar’. Note that this function can take any number of input strings.
array<struct<string,double>> context_ngrams(array<array>, array, int K, int pf) Returns the top-k contextual N-grams from a set of tokenized sentences, given a string of “context”. See StatisticsAndDataMining for more information.
string concat_ws(string SEP, string A, string B…) Like concat() above, but with custom separator SEP.
string concat_ws(string SEP, array) Like concat_ws() above, but taking an array of strings. (as of Hive 0.9.0)
int find_in_set(string str, string strList) 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. e.g. find_in_set(‘ab’, ‘abc,b,ab,c,def’) returns 3
string format_number(number x, int d) Formats the number X to a format like ‘#,###,###.##’, rounded to D decimal places, and returns the result as a string. If D is 0, the result has no decimal point or fractional part. (as of Hive 0.10.0)
string get_json_object(string json_string, string path) Extract json object from a json string based on json path specified, and return json string of the extracted json object. It will return null if the input json string is invalid.NOTE: The json path can only have the characters [0-9a-z_], i.e., no upper-case or special characters. Also, the keys *cannot start with numbers.* This is due to restrictions on Hive column names.
boolean in_file(string str, string filename) Returns true if the string str appears as an entire line in filename.
int instr(string str, string substr) Returns the position of the first occurence of substr in str
int length(string A) Returns the length of the string
int locate(string substr, string str[, int pos]) Returns the position of the first occurrence of substr in str after position pos
string lower(string A) lcase(string A)
string lpad(string str, int len, string pad) Returns str, left-padded with pad to a length of len
string ltrim(string A) Returns the string resulting from trimming spaces from the beginning(left hand side) of A e.g. ltrim(‘ foobar ‘) results in ‘foobar ‘
array<struct<string,double>> ngrams(array<array >, int N, int K, int pf) Returns the top-k N-grams from a set of tokenized sentences, such as those returned by the sentences() UDAF. See StatisticsAndDataMining for more information.
string parse_url(string urlString, string partToExtract [, string keyToExtract]) Returns the specified part from the URL. Valid values for partToExtract include HOST, PATH, QUERY, REF, PROTOCOL, AUTHORITY, FILE, and USERINFO. e.g. parse_url(‘http://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1’, ‘HOST’) returns ‘facebook.com’. Also a value of a particular key in QUERY can be extracted by providing the key as the third argument, e.g. parse_url(‘http://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1’, ‘QUERY’, ‘k1’) returns ‘v1’.
string printf(String format, Obj… args) Returns the input formatted according do printf-style format strings (as of Hive 0.9.0)
string regexp_extract(string subject, string pattern, int index) Returns the string extracted using the pattern. e.g. regexp_extract(‘foothebar’, ‘foo(.*?)(bar)’, 2) returns ‘bar.’ Note that some care is necessary in using predefined character classes: using ‘\s’ as the second argument will match the letter s; ‘s’ is necessary to match whitespace, etc. The ‘index’ parameter is the Java regex Matcher group() method index. See docs/api/java/util/regex/Matcher.html for more information on the ‘index’ or Java regex group() method.
string regexp_replace(string INITIAL_STRING, string PATTERN, string REPLACEMENT) Returns the string resulting from replacing all substrings in INITIAL_STRING that match the java regular expression syntax defined in PATTERN with instances of REPLACEMENT, e.g. regexp_replace(“foobar”, “oo|ar”, “”) returns ‘fb.’ Note that some care is necessary in using predefined character classes: using ‘\s’ as the second argument will match the letter s; ‘s’ is necessary to match whitespace, etc.
string repeat(string str, int n) Repeat str n times
string reverse(string A) Returns the reversed string
string rpad(string str, int len, string pad) Returns str, right-padded with pad to a length of len
string rtrim(string A) Returns the string resulting from trimming spaces from the end(right hand side) of A e.g. rtrim(‘ foobar ‘) results in ‘ foobar’
array<array> sentences(string str, string lang, string locale) Tokenizes a string of natural language text into words and sentences, where each sentence is broken at the appropriate sentence boundary and returned as an array of words. The ‘lang’ and ‘locale’ are optional arguments. e.g. sentences(‘Hello there! How are you?’) returns ( (“Hello”, “there”), (“How”, “are”, “you”) )
string space(int n) Return a string of n spaces
array split(string str, string pat) Split str around pat (pat is a regular expression)
map<string,string> str_to_map(text[, delimiter1, delimiter2]) Splits text into key-value pairs using two delimiters. Delimiter1 separates text into K-V pairs, and Delimiter2 splits each K-V pair. Default delimiters are ‘,’ for delimiter1 and ‘=’ for delimiter2.
string substr(string|binary A, int start) substring(string|binary A, int start) Returns the substring or slice of the byte array of A starting from start position till the end of string A e.g. substr(‘foobar’, 4) results in ‘bar’
string substr(string|binary A, int start, int len) substring(string|binary A, int start, int len) Returns the substring or slice of the byte array of A starting from start position with length len e.g. substr(‘foobar’, 4, 1) results in ‘b’
string translate(string input, string from, string to) Translates the input string by replacing the characters present in the from string with the corresponding characters in the to string. This is similar to the translatefunction in PostgreSQL. If any of the parameters to this UDF are NULL, the result is NULL as well (available as of Hive 0.10.0)
string trim(string A) Returns the string resulting from trimming spaces from both ends of A e.g. trim(‘ foobar ‘) results in ‘foobar’
string upper(string A) ucase(string A) Returns the string resulting from converting all characters of A to upper case e.g. upper(‘fOoBaR’) results in ‘FOOBAR’

Collection Functions

The following built-in collection functions are supported in hive:

Return Type Name(Signature) Example
int size(Map) Returns the number of elements in the map type
int size(Array) Returns the number of elements in the array type
array map_keys(Map) Returns an unordered array containing the keys of the input map
array map_values(Map) Returns an unordered array containing the values of the input map
boolean array_contains(Array, value) Returns TRUE if the array contains value
array sort_array(Array) Sorts the input array in ascending order according to the natural ordering of the array elements and returns it (as of version 0.9.0)

Built-in Aggregate Functions (UDAF)

The following are built-in aggregate functions are supported in Hive:

Return Type Name(Signature) Example
bigint count(*), count(expr), count(DISTINCT expr[, expr_.]) count(*) – Returns the total number of retrieved rows, including rows containing NULL values; count(expr) – Returns the number of rows for which the supplied expression is non-NULL; count(DISTINCT expr[, expr]) – Returns the number of rows for which the supplied expression(s) are unique and non-NULL.
double sum(col), sum(DISTINCT col) Returns the sum of the elements in the group or the sum of the distinct values of the column in the group
double avg(col), avg(DISTINCT col) Returns the average of the elements in the group or the average of the distinct values of the column in the group
double min(col) Returns the minimum of the column in the group
double max(col) Returns the maximum value of the column in the group
double variance(col), var_pop(col) Returns the variance of a numeric column in the group
double var_samp(col) Returns the unbiased sample variance of a numeric column in the group
double stddev_pop(col) Returns the standard deviation of a numeric column in the group
double stddev_samp(col) Returns the unbiased sample standard deviation of a numeric column in the group
double covar_pop(col1, col2) Returns the population covariance of a pair of numeric columns in the group
double covar_samp(col1, col2) Returns the sample covariance of a pair of a numeric columns in the group
double corr(col1, col2) Returns the Pearson coefficient of correlation of a pair of a numeric columns in the group
double percentile(BIGINT col, p) Returns the exact pth percentile of a column in the group (does not work with floating point types). p must be between 0 and 1. NOTE: A true percentile can only be computed for integer values. Use PERCENTILE_APPROX if your input is non-integral.
array percentile(BIGINT col, array(p1 [, p2]…)) Returns the exact percentiles p1, p2, … of a column in the group (does not work with floating point types). pi must be between 0 and 1. NOTE: A true percentile can only be computed for integer values. Use PERCENTILE_APPROX if your input is non-integral.
double percentile_approx(DOUBLE col, p [, B]) Returns an approximate pth percentile of a numeric column (including floating point types) in the group. The B parameter controls approximation accuracy at the cost of memory. Higher values yield better approximations, and the default is 10,000. When the number of distinct values in col is smaller than B, this gives an exact percentile value.
array percentile_approx(DOUBLE col, array(p1 [, p2]…) [, B]) Same as above, but accepts and returns an array of percentile values instead of a single one.
array histogram_numeric(col, b) Computes a histogram of a numeric column in the group using b non-uniformly spaced bins. The output is an array of size b of double-valued (x,y) coordinates that represent the bin centers and heights
array collect_set(col) Returns a set of objects with duplicate elements eliminated

Built-in Table-Generating Functions (UDTF)

Normal user-defined functions, such as concat(), take in a single input row and output a single output row. In contrast, table-generating functions transform a single input row to multiple output rows.

Return Type Name(Signature) Example
inline(ARRAY<STRUCT[,STRUCT]>) Explodes an array of structs into a table (as of Hive 0.10)
Explode explode() takes in an array as an input and outputs the elements of the array as separate rows. UDTF’s can be used in the SELECT expression list and as a part of LATERAL VIEW.

Conditional Functions

Return Type Name(Signature) Example
T if(boolean testCondition, T valueTrue, T valueFalseOrNull) Return valueTrue when testCondition is true, returns valueFalseOrNull otherwise
T COALESCE(T v1, T v2, …) Return the first v that is not NULL, or NULL if all v’s are NULL
T CASE a WHEN b THEN c [WHEN d THEN e]* [ELSE f] END When a = b, returns c; when a = d, return e; else return f
T CASE WHEN a THEN b [WHEN c THEN d]* [ELSE e] END When a = true, returns b; when c = true, return d; else return e

Functions for Text Analytics

Return Type Name(Signature) Example
array<struct<string,double>> context_ngrams(array<array>, array, int K, int pf) Returns the top-k contextual N-grams from a set of tokenized sentences, given a string of “context”. See StatisticsAndDataMining for more information.N-grams are subsequences of length N drawn from a longer sequence. The purpose of the ngrams() UDAF is to find the k most frequent n-grams from one or more sequences. It can be used in conjunction with the sentences() UDF to analyze unstructured natural language text, or the collect() function to analyze more general string data.
array<struct<string,double>> ngrams(array<array>, int N, int K, int pf) Returns the top-k N-grams from a set of tokenized sentences, such as those returned by the sentences() UDAF. See StatisticsAndDataMining for more information.Contextual n-grams are similar to n-grams, but allow you to specify a ‘context’ string around which n-grams are to be estimated. For example, you can specify that you’re only interested in finding the most common two-word phrases in text that follow the context “I love”. You could achieve the same result by manually stripping sentences of non-contextual content and then passing them to ngrams(), but context_ngrams() makes it much easier.
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