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Motivation

Now many watermark-related features such as the watermark alignment have been implemented on the datastream API, and it is very convenient and flexible to configure and use these features through the datastream API. However, there is currently no way to use these features through SQL.

...

CREATE TABLE user_actions (
  user_name STRING,
  `data` STRING,
  current_time as CURRENT_TIMESTAMPproctime(),
  WATERMARK FOR current_time AS current_time
) WITH (
  ...
);

...

-- configure in table options
CREATE TABLE user_actions (
  ...
  user_action_time TIMESTAMP(3),
  WATERMARK FOR user_action_time AS user_action_time - INTERVAL '5' SECOND
) WITH (
  'scan.watermark.idle-timeout'='1min',
  ...
);

-- use 'OPTIONS' hint
select ... from source_table /*+ OPTIONS('scan.watermark.idle-timeout'='1min') */

3.Watermark alignment

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Note source connectors have to implement watermark alignment of source split in order to use the watermark alignment feature since 1.17 according flip-217 [2]. If source connector does not implement flip-217, the task will run with an error, user could set `pipeline'pipeline.watermark-alignment.allow-unaligned-source-splits` to true splits'= 'true' to disable watermark alignment of source split, and watermark alignment will be working properly only when your number of splits equals to the parallelism of the source operator.

...

'scan.watermark.emit.strategy'='on-event',
'scan.watermark.idle-timeout'='1min',
'scan.watermark.alignment.group'='alignment-group-1',
'scan.watermark.alignment.max-drift'='1min',
'scan.watermark.alignment.update-interval'='1s'

...

To describe the watermark launch emit strategy, we need to add an enumeration class:

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