prestodb/presto · error · PrestoException

DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION

DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION

Error message

Unsupported pushdown for Druid connector with plan node of type ${node}

What it means

DruidQueryGenerator's Visitor.visitPlan is the default fallback for any PlanNode type the Druid query generator does not implement. Hitting it means the plan subtree contains a node type the connector cannot translate into a Druid query, so pushdown is refused with DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION.

Source

Thrown at presto-druid/src/main/java/com/facebook/presto/druid/DruidQueryGenerator.java:186

                    .add("pushdown", pushdown)
                    .toString();
        }
    }

    private class DruidQueryPlanVisitor
            extends PlanVisitor<DruidQueryGeneratorContext, DruidQueryGeneratorContext>
    {
        private final ConnectorSession session;

        protected DruidQueryPlanVisitor(ConnectorSession session)
        {
            this.session = session;
        }

        @Override
        public DruidQueryGeneratorContext visitPlan(PlanNode node, DruidQueryGeneratorContext context)
        {
            throw new PrestoException(DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION, "Unsupported pushdown for Druid connector with plan node of type " + node);
        }

        protected VariableReferenceExpression getVariableReference(RowExpression expression)
        {
            if (expression instanceof VariableReferenceExpression) {
                return ((VariableReferenceExpression) expression);
            }
            throw new PrestoException(DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION, "Unsupported pushdown for Druid connector. Expect variable reference, but get: " + expression);
        }

        @Override
        public DruidQueryGeneratorContext visitMarkDistinct(MarkDistinctNode node, DruidQueryGeneratorContext context)
        {
            requireNonNull(context, "context is null");
            return node.getSource().accept(this, context);
        }

        @Override

View on GitHub (pinned to 55bb57d202)

Solutions

1. Identify the unsupported node via EXPLAIN and restructure the query to avoid it above the Druid scan (e.g. avoid window functions/joins in the pushed-down portion).
2. Force partial (non-whole-plan) pushdown or disable pushdown for the query so unsupported nodes execute in Presto.
3. Split the query into a pushdown-friendly inner query over Druid plus outer processing in Presto.
4. Upgrade or patch the connector to add a visit override for the node type.

Example fix

// before
SELECT lag(cnt) OVER (ORDER BY day) FROM druid_agg;
// after
SELECT day, cnt FROM druid_agg; -- compute lag in Presto/client outside pushed-down scan

// Restrict plan shape before pushdown: only scan/project/filter/aggregation
boolean pushablePlan(PlanNode n) {
    return n instanceof ScanFilterProjectNode || n instanceof ProjectNode
        || n instanceof FilterNode || n instanceof AggregationNode;
}

boolean isUnsupportedNode(PlanNode n) {
    return n instanceof WindowNode || n instanceof TopNNode || n instanceof SortNode
        || n instanceof UnnestNode || n instanceof JoinNode;
}

try { druidQuery = new DruidQueryGenerator(plan, session).generate(); }
catch (PrestoException e) {
    if (e.getErrorCode().getName().equals("DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION")) { executePartialPushdown(plan); }
    else throw e;
}

When it happens

Trigger: node.getSource().accept(this, ...) reaches a PlanNode subclass without a visit override (e.g. WindowNode, TopNNode, UnnestNode, SortNode, JoinNode, etc.) during Druid query generation.

Common situations: Queries with window functions, DISTINCT-beyond-MarkDistinct shapes, unnest, sorts, or joins over a Druid table that the planner attempted to push down; plans changed by new optimizer rules in a Presto upgrade.

Related errors

• DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION
• DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION
• DRUID_PUSHDOWN_UNSUPPORTED_EXPRESSION
• DRUID_BROKER_RESULT_ERROR
• DRUID_BROKER_RESULT_ERROR

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/6e3dcf7bf21f4122. Report an issue: GitHub.