Hive Metastore Derby DB

If you are using Hive in default mode, you may see the following behavior – you get to hive client from different directories and see different results when you run a query like “show tables”.  For example, you have hive installed in /usr/local/hive and your are currently in your home directory and run

~> /usr/local/hive/bin/hive    #– get to hive
hive> create table new_table (c1 string);
hive> show tables;

Now you will see “new_table” in the list.

~> cd /tmp
/tmp> /usr/local/hive/bin/hive   #– get to hive
hive> show tables;

Now you don’t see “new_table” in your list of tables.  Those who come from typical SQL background may find it little weird in the beginning due to fact that results seem different depending on from where you started the hive client.  The reason  is because hive uses “embedded Derby” database to store meta data and one of the default configuration property is to use the current directory to store metastore_db.

On starting the hive from two different directories like above, one would see two “metastore_db” directories  created in home (~) and /tmp directories.  You can change this and use one metastore_db by updating “/usr/local/hive/conf/hive-default.xml” file’s “javax.jdo.option.ConnectionURL” as below.

Default setting:
   
      javax.jdo.option.ConnectionURL
      jdbc:derby:;databaseName=metastore_db;create=true
      JDBC connect string for a JDBC metastore
   

Update it to:
   
      javax.jdo.option.ConnectionURL
      jdbc:derby:;databaseName=/home/hadoop/metastore_db;create=true
      JDBC connect string for a JDBC metastore
   

“/home/hadoop” is an example and one can appropriately change it to suitable host and directory.  Say,
jdbc:derby:;databaseName=//localhost:1234/metastore_db;create=true

Cheers,
Shiva