CREATE CHANGEFEED attempts to create a "{_family_}" topic in downstream sink

[smcvey]

Describe the problem

Creating a changefeed on a multi-family table with the split_column_families attempts to create a topic called "{family}" on the broker, despite this not being the name of any column family defined in the table.

To Reproduce

• Create a new cluster, single node is enough. Have a downstream broker such as Kafka/Redpanda with automatic topic creation enabled.

• Run the following SQL:

CREATE TABLE t (
    id UUID PRIMARY KEY,
    s STRING,
    FAMILY "a" (id),
    FAMILY "b" (s)); -- two column families, called a and b

CREATE CHANGEFEED FOR TABLE t INTO '<kafka sink address>' WITH OPTIONS (split_column_families);

Without populating the table with any entries, if I go and look at the created topics, I see one that shouldn't be there:

NAME                    PARTITIONS  REPLICAS
t._u007b_family_u007d_  1           1

This topic does not show up on 23.2.x, but it does show up in 24.1.x and 24.2.x. However, all versions (including 23.2.x) show this nonsense notice message:

NOTICE: changefeed will emit to topic t._u007b_family_u007d_

With a broker that doesn't automatically create topics, the changefeed cannot start up and produces the following log message:

Changefeed job <job id> encountered transient error: ‹kafka server: Request was for a topic or partition that does not exist on this broker› (attempt 1)

Expected behavior

It should not attempt to create a {_family_} topic, especially as this topic doesn't receive any messages. This breaks changefeeds that send to a broker that has disabled automatic topic creation as they cannot start up. Also the above NOTICE message should not be produced.

Environment:

• CockroachDB version: 23.2.x (for the NOTICE message), 24.1.x and 24.2.x for the NOTICE and message creation.

Jira issue: CRDB-41314

[blathers-crl[bot]]

Hi @smcvey, please add branch-* labels to identify which branch(es) this C-bug affects.

_{:owl: Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[blathers-crl[bot]]

cc @cockroachdb/cdc