abhishekrb19 opened a new pull request, #15495:
URL: https://github.com/apache/druid/pull/15495
Problem:
The MSQ engine requires data rows to be produced with an Insert or Replace
query. A query that produces 0 rows would result in an `InsertCannotBeEmpty`
MSQ fault, requiring a user to validate and adjust their query so that the
query produces non-empty rows to succeed.
Description:
- Introduce a new query context `failOnEmptyInsert`, which defaults to false.
- When `failOnEmptyInsert` is:
- `false`, the default behavior, MSQE will allow empty inserts and
replaces.
- `true`, MSQE will throw the existing `InsertCannotBeEmpty` MSQ fault.
- The controller query kernel has a method `isStageOutputEmpty(int stageId)`
that determines if a stage output is empty, non-empty or unknown using the
cluster key statistics.
- For a `REPLACE ALL` query over an existing `ALL` grain segment, the query
will generate a tombstone spanning eternity which will be removed eventually be
the coordinator [duty](https://github.com/apache/druid/pull/15281), so
subsequent data can be appended. This would be effectively similar to a
`DELETE` table command as the eternity tombstone will mask all the underlying
data.
- Add unit tests in `MSQInsertTest`, `MSQReplaceTest` to test the new
default behavior (i.e., when `failOnEmptyInsert = false`)
- Update unit tests in MSQFaultsTest to test the non-default behavior (i.e.,
when `failOnEmptyInsert = true`)
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Introduce a MSQ query context, `failOnEmptyInsert`, which determines whether
an insert or replace query should succeed or fail if it results in an empty
result set. The default behavior is false and MSQE will allow empty inserts and
replaces in this mode. When `failOnEmptyInsert` is set to true, MSQE will throw
the `InsertCannotBeEmpty` fault.
<hr>
##### Key changed/added classes in this PR
* `ControllerImpl.java`
* `ControllerQueryKernel.java`
* `TombstoneHelper.java`
<hr>
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This PR has:
- [x] been self-reviewed.
- [x] added documentation for new or modified features or behaviors.
- [x] a release note entry in the PR description.
- [x] added Javadocs for most classes and all non-trivial methods. Linked
related entities via Javadoc links.
- [x] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold for [code
coverage](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md)
is met.
- [x] been tested in a test Druid cluster.
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