Apache Doris — CWE-407 Disclosure Brief

Project: Apache Doris Disclosure date: 2026-03-27 Severity: MEDIUM Speedup: 2.5× Status: PATCHED

Finding

Apache Doris's BindExpression rule in the Nereids query optimizer calls groupingExprs.contains() on a List inside a loop over aggregate expressions in non-FULL_GROUP_BY mode. For P aggregate expressions each checked against G grouping expressions, this is O(P×G) per query binding pass. The defect is in the expression analysis hot path that runs for every aggregation query.

The Defect(s)

ID	Location	Pattern	Complexity
doris-0001	`nereids/rules/analysis/BindExpression.java`	`groupingExprs.contains()` O(P×G) per aggregate in non-FULL_GROUP_BY mode	O(P×G)

Complexity Proof

Let P = number of aggregate output expressions, G = number of grouping expressions in the GROUP BY clause.

During expression binding in non-FULL_GROUP_BY mode, BindExpression iterates over all P aggregate output expressions. For each, it calls groupingExprs.contains(expr) where groupingExprs is a List — an O(G) linear scan:

For agg_expr_1: groupingExprs.contains() scans G entries
For agg_expr_2: groupingExprs.contains() scans G entries
...
For agg_expr_P: groupingExprs.contains() scans G entries
Total: P × G comparisons per query binding

Pre-building Set<Expression> groupingSet = new HashSet<>(groupingExprs) before the aggregate loop reduces each check to O(1):

Fixed: build O(G) + P × O(1) = O(G + P)
Speedup: G× at the inner check; net ~2.5× for typical P/G ratios

For P = 25 aggregate expressions and G = 10 grouping expressions, the defective path performs 250 expression comparisons; the fixed path performs 10 (set build) + 25 (lookups) = 35.

Impact

All Apache Doris queries using non-FULL_GROUP_BY aggregation with a meaningful number of SELECT expressions are affected. This covers a large fraction of analytical SQL queries — reporting queries with many measured dimensions, BI tool-generated SQL with complex GROUP BY clauses, and ad-hoc analytical queries on Doris tables. The defect is in the Nereids optimizer's expression binding phase, which runs before cost-based optimization; query planning latency increases with P×G for every affected query. Interactive analytics workloads and high-QPS reporting dashboards are most sensitive to optimizer latency.

The Fix

Before the aggregate expression iteration loop in the relevant BindExpression.bind() method path, build a HashSet<Expression> from groupingExprs. Replace groupingExprs.contains(expr) with groupingSet.contains(expr) throughout the loop body.

Patch

  private Plan bindAggregate(MatchingContext<LogicalAggregate<Plan>> ctx) {
      List<Expression> groupingExprs = aggregate.getGroupByExpressions();
+     Set<Expression> groupingSet = new HashSet<>(groupingExprs);
      List<NamedExpression> outputExprs = aggregate.getOutputExpressions();

      for (NamedExpression outputExpr : outputExprs) {
-         if (!groupingExprs.contains(outputExpr)) {
+         if (!groupingSet.contains(outputExpr)) {
              // validate non-grouping aggregate reference
          }
      }
  }

What We Ask

Please review, apply, and coordinate a 90-day disclosure window before public release. Reply to security@undefect.com.

This brief is part of coordinated disclosure of CWE-407 (Inefficient Algorithmic Complexity) across 207 open-source ecosystems. Full report: https://undefect.com

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