[FLINK-25628] Introduce RecordReader and related classes for table store

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: table-store-0.1.0
• Component/s: Table Store
• Labels: pull-request-available
• Assignee: Jingsong Lee
• Reporter: Jingsong Lee
• Created: 12/Jan/22 12:01
• Updated: 14/Feb/22 08:32
• Resolved: 13/Jan/22 08:56

Description

• Introduce RecordReader interface: The reader that reads the batches of records. 
• Introduce SortMergeReader: This reader is to read a list of `RecordReader`, which is already sorted by key and sequence number, and perform a sort merge algorithm. `KeyValue` with the same key will also be combined during sort merging.
• Introduce ConcatRecordReader: This reader is to concatenate a list of `RecordReader` and read them sequentially. The input list is already sorted by key and sequence number, and the key intervals do not overlap each other.
• Introduce FieldStats: Statistics for each field.
• Introduce SstPathFactory: Factory which produces new Path for sst files.
• Introduce SstFile and SstFileMeta: This SstFile includes several `KeyValue`, representing the changes inserted into the file storage.

Issue Links

• links to: GitHub Pull Request #4