This page is meant as a template for writing a FLIP. To create a FLIP choose Tools->Copy on this page and modify with your content and replace the heading with the next FLIP number and a description of your issue. Replace anything in italics with your own description.
Status
Current state: "Under Discussion"
Discussion thread: here (<- link to https://mail-archives.apache.org/mod_mbox/flink-dev/)
JIRA: here (<- link to https://issues.apache.org/jira/browse/FLINK-XXXX)
Released: 1.13
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
Schema information is necessary at different locations in the Table API for defining tables and/or views. In particular, it is necessary to define the schema in a programmatic DDL (FLIP-129) and when converting a DataStream to a Table (FLIP-136).
We need similar APIs in the Catalog interfaces such that catalog implementations can define table/views in a unified way.
Furthermore, a catalog implementation needs a way to encode/decode a schema into properties.
Similar to classes such as Expression/ResolvedExpression or UnresolvedDataType/DataType, a schema should be provided in an unresolved and resolved variant. Currently, TableSchema is a hybrid between resolved and unresolved schema which leads to methods such as
CatalogTableSchemaResolver.resolve(TableSchema): TableSchema
where the updated content of the schema is not directly visible.
This FLIP updates the class hierarchy to achieve the following goals:
- make it visible whether a schema is resolved or unresolved
- offer a unified API for FLIP-129, FLIP-136, and catalogs
- allow arbitrary data types and expressions in the schema for watermark spec or computed columns
- have access to other catalogs for declaring a data type or expression via CatalogManager
- cleaned up TableSchema
- remain backwards compatible in the persisted properties and API
Public Interfaces
Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.
A public interface is any change to the following:
Binary log formatThe network protocol and api behaviorAny class in the public packages under clientsConfiguration, especially client configurationorg/apache/kafka/common/serializationorg/apache/kafka/commonorg/apache/kafka/common/errorsorg/apache/kafka/clients/producerorg/apache/kafka/clients/consumer (eventually, once stable)
MonitoringCommand line tools and argumentsAnything else that will likely break existing users in some way when they upgrade
Proposed Changes
Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.
Compatibility, Deprecation, and Migration Plan
- What impact (if any) will there be on existing users?
- If we are changing behavior how will we phase out the older behavior?
- If we need special migration tools, describe them here.
- When will we remove the existing behavior?
Test Plan
Describe in few sentences how the FLIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?
Rejected Alternatives
If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.