[FLINK-27849] Harden correctness for non-deterministic updates present in the changelog pipeline

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Fix Version/s: 1.20.0
• Component/s: Table SQL / Runtime
• Release Note: For complex streaming jobs, now it's possible to detect and resolve potential correctness issues before running.
• Flags: Important
• Assignee: lincoln lee
• Reporter: lincoln lee
• Created: 31/May/22 06:54
• Updated: 11/Mar/24 12:44

Description

There commonly exists updates(which means not only RowKind.INSERT messages) in a streaming pipeline, then wrong results or error may occurs when use some non-deterministic functions or operations.

It is a long lived issue since the first day that flink sql was available in streaming, but it still not totally be eliminated though some efforts have been taken.

We should detect all the non-deterministic operations in the changelog pipelines, raise an error to tell users the risk and also add an mechanism that can process such a issue if a user is willing to pay some cost(probably introduce the state).

All non-deterministic operations include builtin temporal functions(now, current_timestamp...), UUID, RAND...
or user defined non-deterministic functions (override isDeterministic return false)
or a lookup join on a lookup source which data may change over time

or a cdc-source with meta data field (described in FLINK-28242)

 

 

====== Solution  ======

Will introduce a physical plan checker to validate if there's any non-deterministic updates which may cause wrong result, and also a physical plan rewriter to eliminate the non determinism generated by lookup join node (which we think is commonly used in sql, and hard to solve by users themselves).

For implementation steps, the main changes may include 4 parts:

1. [preparing work] Adds an internal postOptimize method for physical dag processing
2. Introduces a `StreamNonDeterministicPlanResolver` to validate if there's any non-deterministic updates which may cause wrong result and rewrite lookup join node with materialization (to eliminate the non determinism generated by lookup join node)
3. Implements a new lookup join operator (sync mode only) with state to eliminate the non determinism
4. [optimization] SinkUpsertMaterializer should be aware of the input upsertKey if it is not empty

 

 

 

 

 

Issue Links

• duplicates: FLINK-28242 CDC source with meta columns may cause error result on downstream stateful operators
• fixes: FLINK-27639 Flink JOIN uses the now() function when inserting data, resulting in data that cannot be deleted
• relates to: FLINK-27639 Flink JOIN uses the now() function when inserting data, resulting in data that cannot be deleted

Sub-Tasks

• Adds an internal postOptimize method for physical dag processing: Closed
• Adds materialization support to eliminate the non determinism generated by lookup join node: Closed
• Implements a new lookup join operator (sync mode only) with state to eliminate the non determinism: Closed
• Introduces a StreamNonDeterministicPlanResolver to validate and try to solve (lookup join only) the non-deterministic updates problem which may cause wrong result or error: Closed
• [doc] Add a user doc about the correctness for non-deterministic updates: Closed
• Support validating the determinism for StreamPhysicalMatchRecognize: Resolved
• Support extracting all mapping of Calc node's input references: Closed
• Allow metadata columns in NduAnalyzer with ChangelogNormalize: Closed
• Enable metadata columns in NduAnalyzer with retract if non-virtual: Open