What causes "should not create vector writer from MockWaitEpochStateStore" in risingwavelabs/risingwave?

Inject test rows via a store that supports writers (e.g. MemoryStateStore) instead of the mock.

should not create vector writer from MockWaitEpochStateStore

Error message

should not create vector writer from MockWaitEpochStateStore

What it means

A deliberate `panic!` in `MockWaitEpochStateStore::new_vector_writer`. The mock does not implement vector writes; it exists solely to gate progress on epoch releases in DML executor tests. Attempting to create a vector writer means the test writes data through the mock, which is unsupported by design.

Solutions

Inject test rows via a store that supports writers (e.g. MemoryStateStore) instead of the mock.
Update MockWaitEpochStateStore's test usages if a new code path now requires vector writes.
Restrict the mock to its epoch-wait-only role and move data setup to a real backing store.

Example fix

// before
let writer = mock_store.new_vector_writer(opts).await?; // panics
// after
let writer = MemoryStateStore::new().new_vector_writer(opts).await?;

Defensive patterns

Strategy: validation

Validate before calling

// write test data via a supporting store, not the mock
let writer = MemoryStateStore::new().new_vector_writer(opts).await?;

Prevention

Never construct writers from mocks; use a real backing store for data setup.
Re-check mock usage when new write APIs (like vector writers) are adopted.
Restrict MockWaitEpochStateStore to gating epoch progress only.

When it happens

Trigger: Calling `StateStore::new_vector_writer` on a `MockWaitEpochStateStore`, e.g. when a test component tries to ingest data via the vector writer API.

Common situations: DML executor test setup that pipelines test rows through a vector writer; newer executor code paths adopting the vector-writer API and being plugged into the legacy mock.

Related errors

AI-assisted analysis of risingwavelabs/risingwave@6469eb736d (2026-09-11). Data as JSON: /api/errors/49c4f69517e0fbdb. Report an issue: GitHub.

Appendix: source

Thrown at src/stream/src/executor/dml.rs:521

            let rx = self.wait_epoch_release_rx.lock().await.take().unwrap();
            rx.await.unwrap();
            Ok(())
        }

        async fn new_local(&self, _option: NewLocalOptions) -> Self::Local {
            panic!("should not create local state from MockWaitEpochStateStore")
        }

        async fn new_read_snapshot(
            &self,
            _epoch: HummockReadEpoch,
            _options: NewReadSnapshotOptions,
        ) -> StorageResult<Self::ReadSnapshot> {
            panic!("should not read snapshot from MockWaitEpochStateStore")
        }

        async fn new_vector_writer(&self, _options: NewVectorWriterOptions) -> Self::VectorWriter {
            panic!("should not create vector writer from MockWaitEpochStateStore")
        }
    }

    #[tokio::test]
    async fn test_dml_executor() {
        let table_id = TableId::default();
        let schema = Schema::new(vec![
            Field::unnamed(DataType::Int64),
            Field::unnamed(DataType::Int64),
        ]);
        let column_descs = vec![
            ColumnDesc::unnamed(ColumnId::new(0), DataType::Int64),
            ColumnDesc::unnamed(ColumnId::new(1), DataType::Int64),
        ];
        let stream_key = vec![0];
        let dml_manager = Arc::new(DmlManager::for_test());

        let (mut tx, source) = MockSource::channel();

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