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In some rare cases, users may want to explicitly ignore the cached intermediate result. In this case, user needs to give an explicit hint, such as:

table.hint("ignoreCache")

Right now Flink does not have a hint mechanism yet. So before such a hint mechanism is available. Users are not able to explicitly ignore a cached intermediate result.

Cache a stream table

Theoretically speaking, user can also cache a streaming table. The semantic will be store the result somewhere (potentially with a TTL). However, caching a streaming table is usually not that useful. For simplicity, we would not support stream table caching a streaming table in the first implementation. When cache() is invoked on a stream table, it will be treated as a No-Op. This leaves us the room to add caching for streaming stream tables in the future without asking users to change their code.

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