Difference between Pig and Hive? Why have both? [closed]

Question

My background - 4 weeks old in the Hadoop world. Dabbled a bit in Hive, Pig and Hadoop using Cloudera's Hadoop VM. Have read Google's paper on Map-Reduce and GFS (PDF link).

I understand that-

• Pig's language Pig Latin is a shift from(suits the way programmers think) SQL like declarative style of programming and Hive's query language closely resembles SQL.

• Pig sits on top of Hadoop and in principle can also sit on top of Dryad. I might be wrong but Hive is closely coupled to Hadoop.

• Both Pig Latin and Hive commands compiles to Map and Reduce jobs.

My question - What is the goal of having both when one (say Pig) could serve the purpose. Is it just because Pig is evangelized by Yahoo! and Hive by Facebook?

Answer 1

Check out this post from Alan Gates, Pig architect at Yahoo!, that compares when would use a SQL like Hive rather than Pig. He makes a very convincing case as to the usefulness of a procedural language like Pig (vs. declarative SQL) and its utility to dataflow designers.

Answer 2

Hive was designed to appeal to a community comfortable with SQL. Its philosophy was that we don't need yet another scripting language. Hive supports map and reduce transform scripts in the language of the user's choice (which can be embedded within SQL clauses). It is widely used in Facebook by analysts comfortable with SQL as well as by data miners programming in Python. SQL compatibility efforts in Pig have been abandoned AFAIK - so the difference between the two projects is very clear.

Supporting SQL syntax also means that it's possible to integrate with existing BI tools like Microstrategy. Hive has an ODBC/JDBC driver (that's a work in progress) that should allow this to happen in the near future. It's also beginning to add support for indexes which should allow support for drill-down queries common in such environments.

Finally--this is not pertinent to the question directly--Hive is a framework for performing analytic queries. While its dominant use is to query flat files, there's no reason why it cannot query other stores. Currently Hive can be used to query data stored in Hbase (which is a key-value store like those found in the guts of most RDBMSes), and the HadoopDB project has used Hive to query a federated RDBMS tier.