[DBZ-PGYB][yugabyte/yugabyte-db#21591] Support to process update records with CHANGE

[vaibhav-yb]

These changes add the support to the PG connector to stream UPDATE records from the YugabyteDB server.

Summary:

Suppose we execute the following statements:

CREATE TABLE test (pk INT PRIMARY KEY, aa INT, bb TEXT);
INSERT INTO test VALUES (1, 1, 'hello-world'); # Event 1
UPDATE test SET aa = 2 WHERE pk = 1; # Event 2
UPDATE test SET aa = NULL WHERE pk = 1; # Event 3

The payload structure for the above events would be as follows:

1. Event 1: pk:{"value":1,"set":true},aa:{"value":1,"set":true},bb:{"value":"hello-world","set":true}
2. Event 2: pk:{"value":1,"set":true},aa:{"value":2,"set":true},bb:null
3. Event 3: pk:{"value":1,"set":true},aa:{"value":null,"set":true},bb:null

Changes in PR:

1. Added PGTableSchemaBuilder to facilitate custom schema when replica identity is CHANGE.
2. Added transformer to be used in sink connector YBExtractNewRecordState.
3. Streaming and snapshot change event sources now use a modified emitter which also takes the replica identity as a parameter.

[dr0pdb]

A basic question to confirm.

• bb: null means that the value is not being sent. It doesn't mean that the value of column bb is NULL
• bb:{"value":null,"set":true} means that the value is explicitly NULL.

Is this correct?

[vaibhav-yb]

A basic question to confirm.

• bb: null means that the value is not being sent. It doesn't mean that the value of column bb is NULL
• bb:{"value":null,"set":true} means that the value is explicitly NULL.

Is this correct?

@dr0pdb Yes, your understanding is correct.