prestodb/presto · error · PrestoException

NOT_SUPPORTED

NOT_SUPPORTED

Error message

e.getMessage()

What it means

The map subscript operator map[key] throws NOT_SUPPORTED when seekKeyExact raises NotSupportedException because the map's key type cannot be hashed/compared natively. This is the legacy (nullable-result) subscript overload.

Source

Thrown at presto-main-base/src/main/java/com/facebook/presto/operator/scalar/MapSubscriptOperator.java:122

        return new BuiltInScalarFunctionImplementation(
                true,
                ImmutableList.of(
                        valueTypeArgumentProperty(RETURN_NULL_ON_NULL),
                        valueTypeArgumentProperty(RETURN_NULL_ON_NULL)),
                methodHandle);
    }

    @UsedByGeneratedCode
    public static Object subscript(boolean legacyMissingKey, MissingKeyExceptionFactory missingKeyExceptionFactory, MethodHandle keyNativeHashCode, MethodHandle keyBlockNativeEquals, MethodHandle keyBlockHashCode, Type valueType, SqlFunctionProperties properties, Block map, boolean key)
    {
        SingleMapBlock mapBlock = (SingleMapBlock) map;
        int valuePosition;
        try {
            valuePosition = mapBlock.seekKeyExact(key, keyNativeHashCode, keyBlockNativeEquals, keyBlockHashCode);
        }
        catch (NotSupportedException e) {
            throw new PrestoException(NOT_SUPPORTED, e.getMessage(), e);
        }

        if (valuePosition == -1) {
            if (legacyMissingKey) {
                return null;
            }
            throw missingKeyExceptionFactory.create(properties, key);
        }
        return readNativeValue(valueType, mapBlock, valuePosition);
    }

    @UsedByGeneratedCode
    public static Object subscript(boolean legacyMissingKey, MissingKeyExceptionFactory missingKeyExceptionFactory, MethodHandle keyNativeHashCode, MethodHandle keyBlockNativeEquals, MethodHandle keyBlockHashCode, Type valueType, SqlFunctionProperties properties, Block map, long key)
    {
        SingleMapBlock mapBlock = (SingleMapBlock) map;
        int valuePosition;
        try {
            valuePosition = mapBlock.seekKeyExact(key, keyNativeHashCode, keyBlockNativeEquals, keyBlockHashCode);

View on GitHub (pinned to 55bb57d202)

Solutions

  1. Use simple key types for maps.
  2. Restructure data so lookup keys are primitives.
  3. Cast keys to a supported type when constructing the map.
  4. Upgrade Presto if support for the key type exists in newer releases.

Example fix

// before
SELECT m[ROW(1,'a')] FROM t;
// after
SELECT m['1|a'] FROM t; -- varchar key
Defensive patterns

Strategy: try-catch

Validate before calling

SELECT typeof(m) FROM t; -- confirm key type is supported before m[key]

Try / catch

try {
    value = mapSubscript(map, key);
} catch (PrestoException e) {
    if (e.getErrorCode().getName().equals("NOT_SUPPORTED")) {
        value = null; // or scan entries
    }
}

Prevention

When it happens

Trigger: Evaluating map[key] on a map whose key type is a complex type unsupported for native lookup; legacy_missing_key_behavior=true path.

Common situations: Row/array/map-typed keys produced by complex ETL; older configs relying on legacy missing-key behavior.

Understand the failure class

Background: Presto NOT_SUPPORTED error: what "not supported" means and how to fix it — this error's family across 3 libraries.

Related errors

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/e1bf44995cf11333. Report an issue: GitHub.