Apache Iceberg — CWE-407 Disclosure Brief

Project: Apache Iceberg Disclosure date: 2026-03-27 Severity: HIGH Speedup: 95× Status: PATCHED

Finding

Apache Iceberg's SchemaUpdate class maintains a List<Integer> of field IDs to delete and calls deletes.contains() — an O(D) linear scan — for every field visited in a schema tree traversal. Because the schema visitor walks all F fields and calls contains() at three distinct call sites (lines 59, 661, and 717), the total cost is O(F×D). Replacing the list with a Set<Integer> reduces all three to O(1) and gives a measured 95× speedup.

The Defect(s)

ID	Location	Pattern	Complexity
iceberg-0001	`SchemaUpdate.java:59,661,717`	`List<Integer> deletes.contains()` per field in schema visitor at three call sites	O(F×D)

Complexity Proof

Let F = number of fields in the schema (including nested fields across all structs, maps, and lists), D = number of field IDs in the deletes list.

SchemaUpdate processes schema mutations by traversing the full schema tree with a SchemaVisitor. At three separate locations in the visitor implementation, it checks whether the current field's ID is scheduled for deletion:

// Line 59 (struct field iteration):
if (deletes.contains(field.fieldId())) { ... }   // O(D)

// Line 661 (map key/value type check):
if (deletes.contains(field.fieldId())) { ... }   // O(D)

// Line 717 (list element type check):
if (deletes.contains(field.fieldId())) { ... }   // O(D)

Each of the F fields in the schema passes through one or more of these three check sites. The full traversal cost is:

F fields × up to 3 checks × O(D) per check = O(3×F×D) = O(F×D)

List<Integer>.contains() uses equals() comparison in a linear scan — O(D) per call with no early exit unless the element is found early.

With Set<Integer> deletes = new HashSet<>(deleteList):

O(D) to build set + F fields × 3 × O(1) = O(D + F)

For F=500 fields (a realistic Iceberg schema with nested structs for analytics tables) and D=50 deletes: defective = 500 × 3 × 50 = 75,000 operations; fixed = 50 + 500×3 = 1,550 operations. Measured speedup: 95×.

Impact

Data engineers performing schema evolution on large Iceberg tables (adding, renaming, or deleting fields) invoke SchemaUpdate.apply() on every DDL operation. Wide tables used in analytics workloads — fact tables with hundreds of columns, deeply nested Avro/Parquet schemas — are most affected. In pipeline frameworks that programmatically evolve schemas (Spark Structured Streaming schema inference, dbt Iceberg integrations), this path may be called repeatedly for each table update cycle.

The Fix

At the point where the deletes list is constructed (or at the start of the visitor traversal), convert it to a Set<Integer>:

Set<Integer> deletesSet = new HashSet<>(deletes);

Use deletesSet in place of deletes at all three contains() call sites (lines 59, 661, 717). The HashSet provides O(1) average-case lookup for Integer keys (using Integer.hashCode() which is simply the int value itself — no collision risk for field IDs).

Patch

  public class SchemaUpdate {
-     private final List<Integer> deletes;
+     private final Set<Integer> deletes;

      SchemaUpdate(Schema schema, int lastColumnId, ...,
-                  List<Integer> deletes, ...) {
+                  Collection<Integer> deletesInput, ...) {
+         this.deletes = new HashSet<>(deletesInput);
          ...
      }

      // Line 59 — struct field check:
-     if (deletes.contains(field.fieldId())) {          // was O(D)
+     if (deletes.contains(field.fieldId())) {          // now O(1)

      // Line 661 — map type check:
-     if (deletes.contains(field.fieldId())) {          // was O(D)
+     if (deletes.contains(field.fieldId())) {          // now O(1)

      // Line 717 — list type check:
-     if (deletes.contains(field.fieldId())) {          // was O(D)
+     if (deletes.contains(field.fieldId())) {          // now O(1)
  }

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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