Ramin Gharib created FLINK-39302:
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Summary: Handling Idempotency in SHOW CREATE [OR ALTER] for
Relative Intervals
Key: FLINK-39302
URL: https://issues.apache.org/jira/browse/FLINK-39302
Project: Flink
Issue Type: Sub-task
Components: Table SQL / Planner
Reporter: Ramin Gharib
When using relative time intervals (such as {{{}FROM_NOW(INTERVAL '7' DAY){}}})
for materialized table start modes, the expression is inherently non-idempotent
because its evaluated value changes depending on when the command is run.
To ensure clarity and maintain idempotency for users auditing or recreating
tables, the {{SHOW CREATE [OR ALTER] MATERIALIZED TABLE}} command will output
the user's original relative expression, but append an inline SQL comment
containing the exact timestamp that was resolved at the time of execution.
*Example:* If a user submits: {{START_MODE = FROM_NOW(INTERVAL '7' DAY)}}
The {{SHOW CREATE OR ALTER}} output will render as: {{START_MODE =
FROM_NOW(INTERVAL '7' DAY) /* Evaluated to FROM_TIMESTAMP(TIMESTAMP '2025-10-28
10:00:00') at execution */}}
This approach preserves the user's original intent while providing the precise,
deterministic timestamp used by the engine.
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