godfreyhe commented on a change in pull request #12577:
URL: https://github.com/apache/flink/pull/12577#discussion_r440716919
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File path: docs/try-flink/table_api.md
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@@ -462,14 +469,17 @@ public class SpendReport {
tEnv.registerTableSource("transactions", new
UnboundedTransactionTableSource());
tEnv.registerTableSink("spend_report", new SpendReportTableSink());
- tEnv
+ Table table = tEnv
.scan("transactions")
.window(Tumble.over("1.hour").on("timestamp").as("w"))
.groupBy("accountId, w")
- .select("accountId, w.start as timestamp, amount.sum")
- .insertInto("spend_report");
+ .select("accountId, w.start as timestamp, amount.sum");
- env.execute("Spend Report");
+ // trigger execution
+ TableResult tableResult = table.executeInsert("spend_report");
+ // wait job finished
+ tableResult.getJobClient().get()
Review comment:
Thanks for the feedback. agree with you that current api is not friendly
for testing or demos.
For INSERT job, `TableResult.awaitCompletion(timeout)` will work fine. but
for `SELECT` job, there are some problems: in current implementation, client
will send a request to JM (which will re-forward the request to TM) to fetch a
part of result when `Iterator.next()` is called. The sink operator has a
fixed-length pool to buffer the result. If the pool is full, the back-pressure
mechanism will trigger. So the job will not finish until all data has been
fetched to client (or the job is canceled). Code snippet:
```
TableResult tableResult = ...
TableResult.awaitCompletion(timeout);
CloseableIterator<Row> it = TableResult.collect();
it...
```
`TableResult.awaitCompletion(timeout)` will block the execution of
`TableResult.collect()`. This will cause the job will not finish, or get
TimeoutException thrown by `awaitCompletion` method.
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