CTAS doesn't set KEY metadata correctly if key column from left-side of join not included in SELECT

[rmoff]

Create a table (two versions; one retaining existing VALUE_FORMAT of JSON, one changing to Avro) by joining two existing tables:

CREATE TABLE employee_t \
            (key       VARCHAR, \
            name       VARCHAR, \
            watch_flag VARCHAR) \
      WITH (KAFKA_TOPIC ='employees', \
            VALUE_FORMAT ='JSON', \
            KEY='key');

CREATE TABLE computer_t \
            (comp_id INT, \
            empkey   VARCHAR, \
            macaddr  VARCHAR) \
      WITH (KAFKA_TOPIC='computers', \
            VALUE_FORMAT='JSON', \
            KEY='empkey');

CREATE TABLE include_right_key AS \
SELECT e.key     AS EMP_ID,   \
             e.NAME    AS EMP_NAME, \
             e.key     AS EMP_KEY,  \
             c.macaddr AS MACADDR   \
      FROM computer_t c \
            INNER JOIN employee_t e \
            ON c.empkey = e.key ;

CREATE TABLE include_left_key AS \
SELECT c.empkey     AS EMP_ID,   \
             e.NAME    AS EMP_NAME, \
             e.key     AS EMP_KEY,  \
             c.macaddr AS MACADDR   \
      FROM computer_t c \
            INNER JOIN employee_t e \
            ON c.empkey = e.key ;

Inspect the key on the two source tables:

ksql> DESCRIBE EXTENDED COMPUTER_T;

Name                 : COMPUTER_T
Type                 : TABLE
Key field            : EMPKEY
[...]

ksql> DESCRIBE EXTENDED EMPLOYEE_T;

Name                 : EMPLOYEE_T
Type                 : TABLE
Key field            : KEY
[...]

Inspect the key on the created table.

• Works, if the join key column from the left-side of the join is included:

  ksql> DESCRIBE EXTENDED include_left_key;
  
  Name                 : INCLUDE_LEFT_KEY
  Type                 : TABLE
  Key field            : EMP_ID
  [...]
  

• Key not present, if only the join key column from the right-side of the join is included:

  ksql> DESCRIBE EXTENDED include_right_key;
  
  Name                 : INCLUDE_RIGHT_KEY
  Type                 : TABLE
  Key field            :
  [...]
  

[big-andy-coates]

Closing as a duplicate of #2741