= Hive User Defined Functions =
In the CLI, use the commands below to show the latest documentation:
Builtin Operators
Relational Operators
The following operators compare the passed operands and generate a TRUE or FALSE value depending on whether the comparison between the operands holds.
Operator 
Operand types 
Description 
A = B 
All primitive types 
TRUE if expression A is equal to expression B otherwise FALSE 
A == B 
None! 
Fails because of invalid syntax. SQL uses =, not == 
A <> B 
All primitive types 
NULL if A or B is NULL, TRUE if expression A is NOT equal to expression B otherwise FALSE 
A < B 
All primitive types 
NULL if A or B is NULL, TRUE if expression A is less than expression B otherwise FALSE 
A <= B 
All primitive types 
NULL if A or B is NULL, TRUE if expression A is less than or equal to expression B otherwise FALSE 
A > B 
All primitive types 
NULL if A or B is NULL, TRUE if expression A is greater than expression B otherwise FALSE 
A >= B 
All primitive types 
NULL if A or B is NULL, TRUE if expression A is greater than or equal to expression B otherwise FALSE 
A IS NULL 
all types 
TRUE if expression A evaluates to NULL otherwise FALSE 
A IS NOT NULL 
All types 
FALSE if expression A evaluates to NULL otherwise TRUE 
A LIKE B 
strings 
NULL if A or B is NULL, TRUE if string A matches the SQL simple regular expression B, otherwise FALSE. The comparison is done character by character. The _ character in B matches any character in A(similar to . in posix regular expressions) while the % character in B matches an arbitrary number of characters in A(similar to .* in posix regular expressions) e.g. 'foobar' like 'foo' evaluates to FALSE where as 'foobar' like 'foo_ _ _' evaluates to TRUE and so does 'foobar' like 'foo%' 
A RLIKE B 
strings 
NULL if A or B is NULL, TRUE if string A matches the Java regular expression B(See Java regular expressions syntax), otherwise FALSE e.g. 'foobar' rlike 'foo' evaluates to FALSE where as 'foobar' rlike '^f.*r$' evaluates to TRUE 
A REGEXP B 
strings 
Same as RLIKE 
Arithmetic Operators
The following operators support various common arithmetic operations on the operands. All return number types; if any of the operands are NULL, then the result is also NULL.
Operator 
Operand types 
Description 
A + B 
All number types 
Gives the result of adding A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. e.g. since every integer is a float, therefore float is a containing type of integer so the + operator on a float and an int will result in a float. 
A  B 
All number types 
Gives the result of subtracting B from A. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. 
A * B 
All number types 
Gives the result of multiplying A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. Note that if the multiplication causing overflow, you will have to cast one of the operators to a type higher in the type hierarchy. 
A / B 
All number types 
Gives the result of dividing B from A. The result is a double type. 
A % B 
All number types 
Gives the reminder resulting from dividing A by B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. 
A & B 
All number types 
Gives the result of bitwise AND of A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. 
A  B 
All number types 
Gives the result of bitwise OR of A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. 
A ^ B 
All number types 
Gives the result of bitwise XOR of A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. 
~A 
All number types 
Gives the result of bitwise NOT of A. The type of the result is the same as the type of A. 
Logical Operators
The following operators provide support for creating logical expressions. All of them return boolean TRUE, FALSE, or NULL depending upon the boolean values of the operands. NULL behaves as an "unknown" flag, so if the result depends on the state of an unknown, the result itself is unknown.
Operator 
Operand types 
Description 
A AND B 
boolean 
TRUE if both A and B are TRUE, otherwise FALSE. NULL if A or B is NULL 
A && B 
boolean 
Same as A AND B 
A OR B 
boolean 
TRUE if either A or B or both are TRUE; FALSE OR NULL is NULL; otherwise FALSE 
A  B 
boolean 
Same as A OR B 
NOT A 
boolean 
TRUE if A is FALSE or NULL if A is NULL. Otherwise FALSE. 
! A 
boolean 
Same as NOT A 
Complex Type Constructors
The following functions construct instances of complex types.
Constructor Function 
Operands 
Description 
map 
(key1, value1, key2, value2, ...) 
Creates a map with the given key/value pairs 
struct 
(val1, val2, val3, ...) 
Creates a struct with the given field values. Struct field names will be col1, col2, ... 
array 
(val1, val2, ...) 
Creates an array with the given elements 
Operators on Complex Types
The following operators provide mechanisms to access elements in Complex Types
Operator 
Operand types 
Description 
An 
A is an Array and n is an int 
Returns the nth element in the array A. The first element has index 0 e.g. if A is an array comprising of 'foo', 'bar' then A0 returns 'foo' and A1 returns 'bar' 
Mkey 
M is a Map<K, V> and key has type K 
Returns the value corresponding to the key in the map e.g. if M is a map comprising of {'f' > 'foo', 'b' > 'bar', 'all' > 'foobar'} then M'all' returns 'foobar' 
S.x 
S is a struct 
Returns the x field of S. e.g for struct foobar {int foo, int bar} foobar.foo returns the integer stored in the foo field of the struct. 
Builtin Functions
Mathematical Functions
The following builtin mathematical functions are supported in hive; most return NULL when the argument(s) are NULL:
Return Type 
Name(Signature) 
Description 
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 e^a 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 base10 logarithm of the argument 
double 
log2(double a) 
Returns the base2 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 a^p 
double 
sqrt(double a) 
Returns the square root of a 
string 
bin(BIGINT a) 
Returns the number in binary format (see [http://dev.mysql.com/doc/refman/5.0/en/stringfunctions.html#function_bin]) 
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. (see [http://dev.mysql.com/doc/refman/5.0/en/stringfunctions.html#function_hex]) 
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) 
Converts a number from a given base to another (see [http://dev.mysql.com/doc/refman/5.0/en/mathematicalfunctions.html#function_conv]) 
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 
int double 
positive(int a) positive(double a) 
Returns a 
int double 
negative(int a) negative(double a) 
Returns a 
Collection Functions
The following builtin collection functions are supported in hive:
Return Type 
Name(Signature) 
Description 
int 
size(Map<K.V>) 
Returns the number of elements in the map type 
int 
size(Array<T>) 
Returns the number of elements in the array type 
Type Conversion Functions
The following type conversion functions are supported in hive:
Return Type 
Name(Signature) 
Description 
Expected "=" to follow "type" 
cast(expr as <type>) 
Converts the results of the expression expr to <type> e.g. cast('1' as BIGINT) will convert the string '1' to it integral representation. A null is returned if the conversion does not succeed. 
Date Functions
The following builtin date functions are supported in hive:
string 
from_unixtime(bigint unixtime, string format) 
Converts the number of seconds from unix epoch (19700101 00:00:00 UTC) to a string representing the timestamp of that moment in the current system time zone in the format of "19700101 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 
bigint 
unix_timestamp(string date, string pattern) 
Convert time string with given pattern (see [http://java.sun.com/j2se/1.4.2/docs/api/java/text/SimpleDateFormat.html]) to Unix time stamp, return 0 if fail: unix_timestamp('20090320', 'yyyyMMdd') = 1237532400 
string 
to_date(string timestamp) 
Returns the date part of a timestamp string: to_date("19700101 00:00:00") = "19700101" 
int 
year(string date) 
Returns the year part of a date or a timestamp string: year("19700101 00:00:00") = 1970, year("19700101") = 1970 
int 
month(string date) 
Returns the month part of a date or a timestamp string: month("19701101 00:00:00") = 11, month("19701101") = 11 
int 
day(string date) dayofmonth(date) 
Return the day part of a date or a timestamp string: day("19701101 00:00:00") = 1, day("19701101") = 1 
int 
hour(string date) 
Returns the hour of the timestamp: hour('20090730 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("19701101 00:00:00") = 44, weekofyear("19701101") = 44 
int 
datediff(string enddate, string startdate) 
Return the number of days from startdate to enddate: datediff('20090301', '20090227') = 2 
int 
date_add(string startdate, int days) 
Add a number of days to startdate: date_add('20081231', 1) = '20090101' 
int 
date_sub(string startdate, int days) 
Subtract a number of days to startdate: date_sub('20081231', 1) = '20081230' 
Conditional Functions
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 
String Functions
The following are builtin String functions are supported in hive:
Return Type 
Name(Signature) 
Description 
int 
length(string A) 
Returns the length of the string 
string 
reverse(string A) 
Returns the reversed string 
string 
concat(string A, string B...) 
Returns the string resulting from concatenating the strings 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. 
string 
concat_ws(string SEP, string A, string B...) 
Like concat() above, but with custom separator SEP. 
string 
substr(string A, int start) substring(string A, int start) 
Returns the substring of A starting from start position till the end of string A e.g. substr('foobar', 4) results in 'bar' (see [http://dev.mysql.com/doc/refman/5.0/en/stringfunctions.html#function_substr]) 
string 
substr(string A, int start, int len) substring(string A, int start, int len) 
Returns the substring of A starting from start position with length len e.g. substr('foobar', 4, 1) results in 'b' (see [http://dev.mysql.com/doc/refman/5.0/en/stringfunctions.html#function_substr]) 
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' 
string 
lower(string A) lcase(string A) 
Returns the string resulting from converting all characters of B to lower case e.g. lower('fOoBaR') results in 'foobar' 
string 
trim(string A) 
Returns the string resulting from trimming spaces from both ends of A e.g. trim(' foobar ') results in 'foobar' 
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 ' 
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' 
string 
regexp_replace(string A, string B, string C) 
Returns the string resulting from replacing all substrings in B that match the Java regular expression syntax(See Java regular expressions syntax) with C e.g. regexp_replace("foobar", "ooar", "") returns 'fb.' Note that some care is necessary in using predefined character classes: using '\s' as the second argument will match the letter s; ' 
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; ' 
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 
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 09az_, i.e., no uppercase or special characters. Also, the keys *cannot start with numbers.* This is due to restrictions on Hive column names. 
string 
space(int n) 
Return a string of n spaces 
string 
repeat(string str, int n) 
Repeat str n times 
int 
ascii(string str) 
Returns the numeric value of the first character of str 
string 
lpad(string str, int len, string pad) 
Returns str, leftpadded with pad to a length of len 
string 
rpad(string str, int len, string pad) 
Returns str, rightpadded with pad to a length of len 
array 
split(string str, string pat) 
Split str around pat (pat is a regular expression) 
int 
find_in_set(string str, string strList) 
Returns the first occurance of str in strList where strList is a commadelimited 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 
array<array<string>> 
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") ) 
array<struct<string,double>> 
ngrams(array<array<string>>, int N, int K, int pf) 
Returns the topk Ngrams from a set of tokenized sentences, such as those returned by the sentences() UDAF. See HiveStatisticsAndDataMining for more information. 
array<struct<string,double>> 
context_ngrams(array<array<string>>, array<string>, int K, int pf) 
Returns the topk contextual Ngrams from a set of tokenized sentences, given a string of "context". See HiveStatisticsAndDataMining for more information. 
Misc. Functions
xpath
The following functions are described in HiveLanguageManualXPathUDF:
 xpath, xpath_short, xpath_int, xpath_long, xpath_float, xpath_double, xpath_number, xpath_string
get_json_object
A limited version of JSONPath is supported:
 $ : Root object
 . : Child operator
 [] : Subscript operator for array
 * : Wildcard for []
Syntax not supported that's worth noticing:
 : Zero length string as key
 .. : Recursive descent
 @ : Current object/element
 () : Script expression
 ?() : Filter (script) expression.
 , : Union operator
 end.step : array slice operator
Example: src_json table is a single column (json), single row table:
The fields of the json object can be extracted using these queries:
Builtin Aggregate Functions (UDAF)
The following are builtin aggregate functions are supported in Hive:
Return Type* * 
Name(Signature)* * 
Description* * 
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 nonNULL; count(DISTINCT expr, expr)  Returns the number of rows for which the supplied expression(s) are unique and nonNULL. 
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 
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(col, p) 
Returns the exact p^th^ percentile of an integer column in the group (does not work with floating point types). p must be between 0 and 1. 
array<double> 
percentile(col, array(p~1,, , p,,2,,...)) 
Returns the exact percentiles p,,1,,, p,,2,,, ... of an integer column in the group (does not work with floating point types). p,,i~ must be between 0 and 1. 
double 
percentile_approx(col, p , B) 
Returns an approximate p^th^ 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<double> 
Same as above, but accepts and returns an array of percentile values instead of a single one. 

array<struct { 
histogram_numeric(col, b) 
Computes a histogram of a numeric column in the group using b nonuniformly spaced bins. The output is an array of size b of doublevalued (x,y) coordinates that represent the bin centers and heights 
array 
collect_set(col) 
Returns a set of objects with duplicate elements eliminated 
Builtin TableGenerating Functions (UDTF)
<<Anchor(UDTF)>> Normal userdefined functions, such as concat(), take in a single input row and output a single output row. In contrast, tablegenerating functions transform a single input row to multiple output rows.
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.
An example use of explode() in the SELECT expression list is as follows:
Consider a table named myTable that has a single column (myCol) and two rows:
Then running the query:
SELECT explode(myCol) AS myNewCol FROM myTable;
Will produce:
int myNewCol 
1 
2 
3 
4 
5 
6 
Using the syntax "SELECT udtf(col) AS colAlias..." has a few limitations:
 No other expressions are allowed in SELECT
 SELECT pageid, explode(adid_list) AS myCol... is not supported
 UDTF's can't be nested
 SELECT explode(explode(adid_list)) AS myCol... is not supported
 GROUP BY / CLUSTER BY / DISTRIBUTE BY / SORT BY is not supported
 SELECT explode(adid_list) AS myCol ... GROUP BY myCol is not supported
Please see HiveLanguageManualLateralView for an alternative syntax that does not have these limitations.
The following are builtin tablegenerating functions are supported in Hive:
Return Type* * 
Name(Signature)* * 
Description* * 
myType 
explode(array<myType> a) <<Anchor(explode)>> 
For each element in a, explode() generates a row containing that element 
json_tuple
A new json_tuple() UDTF is introduced in hive 0.7. It takes a set of names (keys) and return a tuple of values in one function.
If you are using get_json_object() and want to replace it with json_tuple, the only changes is that your query will be using json_tuple() in lateral view rather than multiple get_json_object() in the select clause.
For example,
should be changed to
GROUPing and SORTing on f(column)
A typical OLAP pattern is that you have a timestamp column and you want to group by daily or other less granular date windows than by second. So you might want to select concat(year(dt),month(dt)) and then group on that concat(). But if you attempt to GROUP BY or SORT BY a column on which you've applied a function and alias, like this:
You will get an error:
Because you are not able to GROUP BY or SORT BY a column alias on which a function has been applied. There are two workarounds. First, you can reformulate this query with subqueries, which is somewhat complicated:
Or you can make sure not to use a column alias, which is simpler:
Contact Tim Ellis (tellis) at RiotGames dot com if you would like to discuss this in further detail.