Return table comments in GetTables Thrift API call and SHOW TABLES statement resultset

When accessing Impala via the Thrift interface the server always returns empty string for the comments/remarks column for the GetTables API call.

It would also be nice if Impala can return table comments for the SHOW TABLES statement. Currently it only returns the table name.

Attached is a simple Java program that uses the open-source Hive JDBC driver to connect to Impala via the Thrift interface and prints out results for the getTables JDBC API call. We notice that the JDBC driver internally uses the GetTables API call to retrieve metadata from Impala for the getTables JDBC API call. The remarks/comments column is always an empty string and it looks like it is because the server always returns empty string for that column.

Impala returns column comments for the GetColumns Thrift API call as well as the DESCRIBE <table> statement.