HCatalog Basics

• HCatalog is an extension of Hive, that exposes the Hive metadata to other tools and frameworks.
• To define a HCatalog schema, one simply needs to define a table in Hive.
• The usefulness of HCatalog is, when one needs to expose the schema outside of Hive i.e to other frameworks - ex : Pig
• To load a table student, managed by HCatalog:
• stu_table= LOAD 'student' USING org.apache.hcatalog.pig.HCatLoader();
• the schema of stu_table is whatever the schema of student is.
• Similarly, to store we use :
• STORE stu_table INTO 'student' USING org.apache.hcatalog.pig.HCatStorer();

• Using PIG shell, we can run Hive DDL command.

• grunt> sql create table movies (
•    title string,
•    rating string,
•    length double)
• partitioned by (genre string)
• stored as ORC;