[FLINK-1444] Add data properties for data sources

• Type: New Feature
• Status: Resolved
• Priority: Minor
• Resolution: Implemented
• Affects Version/s: 0.9
• Component/s: API / DataSet, Runtime / Coordination
• Assignee: Fabian Hueske
• Reporter: Fabian Hueske
• Created: 24/Jan/15 22:21
• Updated: 28/Feb/19 14:30
• Resolved: 20/Feb/15 15:15

Description

This issue proposes to add support for attaching data properties to data sources. These data properties are defined with respect to input splits.
Possible properties are:

• partitioning across splits: all elements of the same key (combination) are contained in one split
• sorting / grouping with splits: elements are sorted or grouped on certain keys within a split
• key uniqueness: a certain key (combination) is unique for all elements of the data source. This property is not defined wrt. input splits.

The optimizer can leverage this information to generate more efficient execution plans.

The InputFormat will be responsible to generate input splits such that the promised data properties are actually in place. Otherwise, the program will produce invalid results.