greenplum 导入数据方式

参考： http://gpdb.docs.pivotal.io/4390/admin_guide/load/topics/g-working-with-file-based-ext-tables.html

• Accessing File-Based External Tables
  External tables enable accessing external files as if they are regular database tables. They are often used to move data into and out of a Greenplum database.
• file:// Protocol
• gpfdist:// Protocol
• gpfdists:// Protocol
• gphdfs:// Protocol
• s3:// Protocol
• Using a Custom Protocol
• Handling Errors in External Table Data