risingwavelabs/risingwave · error

mysql_query function is not supported in streaming mode

Error message

mysql_query function is not supported in streaming mode

What it means

LogicalMySqlQuery represents a query executed via the mysql_query table function, which can only be evaluated in batch mode by pushing the query to the external MySQL source. Streaming execution (materialized views, sources) cannot continuously evaluate such a query, so to_stream deliberately returns an error.

Solutions

1. Do not use mysql_query in materialized views or any streaming query; keep it in ad-hoc batch SELECT statements
2. Use RisingWave's MySQL CDC connector to ingest the table as a streaming source instead of querying per-request
3. Batch-query the data first and persist results to a table/MV via an ingestion pipeline that supports streaming
4. If periodic refresh is acceptable, schedule batch inserts into a table rather than an MV over mysql_query

Example fix

-- before (fails)
CREATE MATERIALIZED VIEW mv AS SELECT * FROM mysql_query('conn_name', 'SELECT * FROM t');
-- after: batch query only, or use CDC source
SELECT * FROM mysql_query('conn_name', 'SELECT * FROM t');
-- streaming alternative: MySQL CDC source + materialized view over the source

-- Pre-check that a definition does not use mysql_query before making it streaming
-- inspect the SQL for the function, e.g. in application code:
-- if /\bmysql_query\s*\(/i.test(sql) rejectStreamingDefinition();

// psql/driver catch
try {
  await conn.query('CREATE MATERIALIZED VIEW mv AS SELECT * FROM mysql_query(...)');
} catch (e) {
  if (String(e.message).includes('mysql_query function is not supported in streaming mode')) {
    // fall back to batch query or set up a CDC source
  }
  throw e;
}

When it happens

Trigger: Creating a materialized view, source, or any streaming plan that contains a mysql_query(...) table function call, causing the stream optimizer to call to_stream on LogicalMySqlQuery.

Common situations: A user runs CREATE MATERIALIZED VIEW AS SELECT * FROM mysql_query(...) expecting live replication of an external MySQL query; envs where teams assume mysql_query can act as a streaming source.

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

• postgres_query function is not supported in streaming mode
• Actor exited unexpectedly
• Array error
• below watermark check condition eval must return bool array
• Chunk operation error

AI-assisted analysis of risingwavelabs/risingwave@6469eb736d (2026-09-11). Data as JSON: /api/errors/ecb6092f20ebc599. Report an issue: GitHub.

Appendix: source

Thrown at src/frontend/src/optimizer/plan_node/logical_mysql_query.rs:107

    fn predicate_pushdown(
        &self,
        predicate: Condition,
        _ctx: &mut PredicatePushdownContext,
    ) -> LogicalPlanRef {
        // No pushdown.
        LogicalFilter::create(self.clone().into(), predicate)
    }
}

impl ToBatch for LogicalMySqlQuery {
    fn to_batch(&self) -> Result<BatchPlanRef> {
        Ok(BatchMySqlQuery::new(self.core.clone()).into())
    }
}

impl ToStream for LogicalMySqlQuery {
    fn to_stream(&self, _ctx: &mut ToStreamContext) -> Result<StreamPlanRef> {
        bail!("mysql_query function is not supported in streaming mode")
    }

    fn logical_rewrite_for_stream(
        &self,
        _ctx: &mut RewriteStreamContext,
    ) -> Result<(PlanRef, ColIndexMapping)> {
        bail!("mysql_query function is not supported in streaming mode")
    }
}

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