RFC: Add shuffle for iceberg sink

[liurenjie1024]

Rendered

[fuyufjh]

IIRC, our common sinks also have such a Shuffle when the sink's PK doesn't match its stream key. cc. @st1page

This is very similar with this design, the only problem is that previously we didn't distinguish partition key from primary key.

[fuyufjh]

Also cc. @xiangjinwu @tabVersion

Previously in channel #wg-new-source-ddl and risingwavelabs/risingwave#9443, we decided to use the sink property primary_key for both PK and partition key, depending on different connectors, for example,

• Kafka upsert sink will use primary_key as partition key & PK
• Kafka append-only sink will use primary_key as partition key only

While this RFC proposes to introduce 2 different properties: partition_key and primary_key respectively, right?

[st1page]

IIRC, our common sinks also have such a Shuffle when the sink's PK doesn't match its stream key

clarify the condition can lead to the issue: when the partition key does not contain the whole stream key.

[liurenjie1024]

While this RFC proposes to introduce 2 different properties: partition_key and primary_key respectively, right?

In fact, by primary_key here I mean stream_key of sink's input. I think for iceberg we don't need user to specify primary_key here?

[st1page]

The optimizer must know the downstream's partition requirements. in the past, we were just concerned about correctness issues such as "make sure the order of operations for the specific key" or "no multiple parallelisms modifying the same key, which can bring dead-lock". And in this RFC, if the downstream system has a stronger partition key to achieving better performance, we can use it as the distribution strategy and the correctness issues should be guaranteed by the downstream system.

About if the user needs to specify the primary_key/partition key in the CREATE SINK statement.

• for kafka/redis, the primary key/partition key has not a table level's catalog or config, user must give it in CREATE SINK statement to define the behavior of the RW sink.
• for MySQL/JDBC, current behavior is that requiring users to specify the primary_key in the CREATE SINK statement. It will be validated in the meta node if the user-specified pk is the same as the JDBC catalog. It is because currently, frontend can not query the JDBC's catalog without java runtime c.c. @StrikeW correct me if I am wrong
• and for iceberg in this RFC, I think user do not need to specify any information in the CREATE SINK because our fe node can get the information from the downstream system's catalog

[ZENOTME]

There is also probability that cardinality of range only partition be ten thousands. E.g. the partition is year, month,day,hour.🤣 But the probability of this may be not high and we can solve it in risingwavelabs/risingwave#12016.

[liurenjie1024]

There is also probability that cardinality of range only partition be ten thousands. E.g. the partition is year, month,day,hour.🤣 But the probability of this may be not high and we can solve it in risingwavelabs/risingwave#12016.

Yes, that's possible in an extreme case: when we are catching up with history data.