Sushanth Sowmyan created HIVE-6405:
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Summary: Support append feature for HCatalog
Key: HIVE-6405
URL: https://issues.apache.org/jira/browse/HIVE-6405
Project: Hive
Issue Type: Bug
Components: HCatalog, Metastore, Query Processor, Thrift API
Reporter: Sushanth Sowmyan
Assignee: Sushanth Sowmyan
HCatalog currently treats all tables as "immutable" - i.e. all tables and
partitions can be written to only once, and not appended. The nuances of what
this means is as follows:
* A non-partitioned table can be written to, and data in it is never updated
from then on unless you drop and recreate.
* A partitioned table may support "appending" of a sort in a manner by adding
new partitions to the table, but once written, the partitions themselves cannot
have any new data added to them.
Hive, on the other hand, does allow us to "INSERT INTO" a table, thus allowing
us append semantics. There is benefit to both of these models, and so, our goal
is as follows:
a) Introduce a notion of an immutable table, wherein all tables are not
immutable by default, and have this be a table property. If this property is
set for a table, and we attempt to write to a table that already has data (or a
partition), disallow "INSERT INTO" into it from hive. This property being set
will allow hive to mimic HCatalog's current immutable-table property. (I'm
going to create a separate sub-task to cover this)
b) As long as that flag is not set, HCatalog should be changed to allow appends
into it as well, and not simply error out if data already exists in a table.
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