Is there a way to get database name in a hive UDF

Question

I am writing a Hive UDF.

I have to get the name of the database (the function is deployed in). Then, I need to access a few files from hdfs depending on the database environment. Can you please help me which function can help with running a HQL query from Hive UDF.

Answer 1

1. write UDF class and prepare jar file

public class MyHiveUdf extends UDF {
    public Text evaluate(String text,String dbName) {
        if(text == null) {
            return null;
        } else {
              return new Text(dbName+"."+text);
        }
    }
}

2. Use this UDF inside hive query like mentioned below

hive> use mydb; OK Time taken: 0.454 seconds

hive> ADD jar /root/MyUdf.jar;
Added [/root/MyUdf.jar] to class path
Added resources: [/root/MyUdf.jar]

hive> create temporary function myUdfFunction as 'com.hiveudf.strmnp.MyHiveUdf';
OK
Time taken: 0.018 seconds

hive> select myUdfFunction(username,current_database()) from users;
Query ID = root_20170407151010_2ae29523-cd9f-4585-b334-e0b61db2c57b
Total jobs = 1
Launching Job 1 out of 1
Number of reduce tasks is set to 0 since there's no reduce operator
Starting Job = job_1491484583384_0004, Tracking URL = http://mac127:8088/proxy/application_1491484583384_0004/
Kill Command = /opt/cloudera/parcels/CDH-5.9.0-1.cdh5.9.0.p0.23/lib/hadoop/bin/hadoop job  -kill job_1491484583384_0004
Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0
2017-04-07 15:11:11,376 Stage-1 map = 0%,  reduce = 0%
2017-04-07 15:11:19,766 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 3.12 sec
MapReduce Total cumulative CPU time: 3 seconds 120 msec
Ended Job = job_1491484583384_0004
MapReduce Jobs Launched:
Stage-Stage-1: Map: 1   Cumulative CPU: 3.12 sec   HDFS Read: 21659 HDFS Write: 381120 SUCCESS
Total MapReduce CPU Time Spent: 3 seconds 120 msec
OK

mydb.user1
mydb.user2
mydb.user3

Time taken: 2.137 seconds, Fetched: 3 row(s)
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