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Dataiku Hive UDFs

This is a collection of UDF for Apache Hive.

Available UDFs

Array operations

array_count_distinct

int array_count_distinct(array<string>)

Counts the number of distinct values in the array

array_count_equals

int array_count_equals(array<int> haystack, int needle)
int array_count_equals(array<double> haystack, double needle)
int array_count_equals(array<string> haystack, string needle)

Returns the number of times the needle is present in the haystack

collect_to_array

This is an aggregation function that gathers all input values and outputs them as an array.

For example

table page_views {
    int visitor_id;
    string page;
}

The query:

select collect_to_array(page) from page_views group by visitor_id;

produces: array<string>, the list of pages viewed for each visitor_id

array_join

array<TYPE> array_join(array<array<TYPE> >)

Joins an array of arrays into a single array containing all elements. This is often used in combination with collect_to_array

For example, if you have:

table A {
    int product_id;
    int day;
    array<string> buying_customers;
}

collect_to_array(buying_customers) will therefore produce array<array>

To get the full list of customers for one product, you can use:

SELECT array_join(collect_to_array(buying_customers)) FROM A GROUP BY product_id;

Windowing functions

Rank

int rank(string in)

While processing a stream of rows, rank will return the number of times it has previously seen the same value of in.

For example, while processing a table:

table a {
    string data;
}

with values:

p1
p1
p2
p2
p2
p3
p4

The query:

select data, rank(data) from a;

would return:

p1   0
p1   1
p2   0
p2   1
p2   2
p3   0
p4   0

Therefore, rank only makes sense on a sorted table.

rank is very useful for sequence analysis

first_of_group, last_of_group

This is an aggregation function.

TYPE1 first_of_group(TYPE1 outColumn, TYPE2 sortColumn)
TYPE1 last_of_group(TYPE1 outColumn, TYPE2 sortColumn)

For each group, these functions will sort the rows of the group by sortColumn, and then output the value of outColumn for the first (resp. last) row, once sorted.

These functions are very useful for processing tables with "updates".

For example:

table user {
    int id;
    int version;
    string email;
    string location;
}

To get the last recorded location for a given user, you can use:

select last_of_group(location, version) FROM user GROUP BY id;

You can use several first_of_group/last_of_group in the same query:

select last_of_group(location, version), last_of_group(email, version) FROM user GROUP BY id;

Copyright and license

Copyright 2013 Dataiku SAS.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this work except in compliance with the License. You may obtain a copy of the License in the LICENSE file, or at:

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.