risingwavelabs/risingwave · error · SinkError::LanceDb

LanceDB sink does not support schema change

Error message

LanceDB sink does not support schema change

What it means

The LanceDB sink's pre_commit explicitly rejects any sink schema change request. RisingWave allows sinks to receive schema-change events, but the LanceDB implementation has not implemented schema evolution, so any non-null schema_change is refused with this error instead of being silently ignored.

Source

Thrown at src/connector/src/sink/lancedb.rs:721

#[async_trait::async_trait]
impl TwoPhaseCommitCoordinator for LanceDbSinkCommitter {
    async fn init(&mut self) -> Result<()> {
        tracing::info!(
            "LanceDB commit coordinator initialized for table '{}'",
            self.config.common.table
        );
        Ok(())
    }

    async fn pre_commit(
        &mut self,
        epoch: u64,
        metadata: Vec<SinkMetadata>,
        schema_change: Option<PbSinkSchemaChange>,
    ) -> Result<Option<Vec<u8>>> {
        if schema_change.is_some() {
            return Err(SinkError::LanceDb(anyhow!(
                "LanceDB sink does not support schema change"
            )));
        }

        let fragments = Self::collect_fragments(&metadata)?;
        if fragments.is_empty() {
            return Ok(None);
        }

        Ok(Some(
            LanceDbPreCommitMetadata {
                sink_id: self.sink_id.clone(),
                epoch,
                fragments,
            }
            .try_into_bytes()?,
        ))
    }

View on GitHub (pinned to 6469eb736d)

Solutions

1. Do not alter the upstream source/MV schema while a LanceDB sink depends on it; drop and recreate the sink after the change
2. Drop the sink, perform the schema change, then recreate the LanceDB sink so it plans against the new schema
3. Check whether your RisingWave version has added LanceDB schema-evolution support and upgrade

Example fix

// before
ALTER TABLE mv ADD COLUMN new_col INT; -- errors: sink does not support schema change
// after
DROP SINK lancedb_sink;
ALTER TABLE mv ADD COLUMN new_col INT;
CREATE SINK lancedb_sink AS SELECT ... INTO lancedb_table ...;

-- before altering an upstream table feeding a LanceDB sink
SELECT sink_name FROM rw_catalog.rw_sinks
WHERE sink_from = '<upstream_table>';  -- drop/recreate these sinks first

fn schema_change_supported(sink_type: &str) -> bool {
    sink_type != "lancedb"
}

match alter_result {
    Err(err) if err.to_string().contains("does not support schema change") => {
        // drop sink, alter, recreate sink
    }
    other => other,
}

When it happens

Trigger: pre_commit is invoked with a non-null PbSinkSchemaChange — i.e., the source or materialized table feeding the sink undergoes a schema change (ALTER ADD/DROP COLUMN, type change) while the LanceDB sink is running.

Common situations: Developer ALTERs an upstream MV or source column after creating a LanceDB sink; automated schema evolution on a streaming job whose downstream sink is LanceDB.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Only AddColumns schema change is supported for Snowflake sin
• Snowflake catalog only supports iceberg sources
• failed to get underlying lance Dataset (table may be remote)
• Lance fragment write task stopped before accepting a record
• LanceDB pre-commit epoch {} does not match commit epoch {}

AI-assisted analysis of risingwavelabs/risingwave@6469eb736d (2026-09-11). Data as JSON: /api/errors/8aeb9cc1ce87b294. Report an issue: GitHub.