Ramin Gharib created FLINK-39913:
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Summary: Improve the error message when a foreground query emits
an upsert changelog
Key: FLINK-39913
URL: https://issues.apache.org/jira/browse/FLINK-39913
Project: Flink
Issue Type: Improvement
Components: Table SQL / API, Table SQL / Planner
Reporter: Ramin Gharib
Assignee: Ramin Gharib
A foreground query (a bare SELECT, collected with no primary key) over a
relation that emits an upsert changelog fails with an unhelpful error. The
message is just "Can't generate a valid execution plan" followed by the
optimized plan. A user has no way to tell what went wrong or how to fix it.
The plan can emit an upsert changelog, for example via FROM_CHANGELOG with
PARTITION BY and an op_mapping that has no UPDATE_BEFORE. The foreground sink
has no primary key, so the planner requires a retract changelog (UPDATE_BEFORE
+ UPDATE_AFTER). Upsert cannot satisfy that, and the planner gives up.
Reproduce:
{code:java}
SELECT *
FROM FROM_CHANGELOG(
input => TABLE events PARTITION BY id,
op => DESCRIPTOR(operation),
op_mapping => MAP[
'c', 'INSERT',
'u', 'UPDATE_AFTER',
'd', 'DELETE'
]
); {code}
Part of the error message the users sees is:
{code:java}
Can't generate a valid execution plan for the given query:
Sink(table=[*anonymous_foreground-sink$112*], fields=[id, name, email,
status, event_time], changelogMode=[NONE])
...{code}
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