prestodb/presto · error · IllegalArgumentException

Unexpected type found: %s

Error message

Unexpected type found: %s

What it means

Recursive value fixer in the client hit a value whose shape does not match any known signature branch (not ARRAY, MAP, ROW, or a recognized scalar), so it cannot normalize the JSON value to the declared type.

Source

Thrown at presto-client/src/main/java/com/facebook/presto/client/FixJsonDataUtils.java:121

            return fixValue(signature.getDistinctTypeInfo().getBaseType(), value);
        }
        if (signature.getTypeSignatureBase().hasTypeName() && signature.getTypeSignatureBase().hasStandardType()) {
            return fixValue(signature.getStandardTypeSignature(), value);
        }
        if (signature.getBase().equals(ARRAY)) {
            if (List.class.isAssignableFrom(value.getClass())) {
                List<Object> fixedValue = new ArrayList<>();
                for (Object object : List.class.cast(value)) {
                    fixedValue.add(fixValue(signature.getTypeOrNamedTypeParametersAsTypeSignatures().get(0), object));
                }
                return fixedValue;
            }
            // JSON keys may be serialized and deserialized as simple strings
            else if (value.getClass() == String.class) {
                List<String> newValue = LIST_JSON_CODEC.fromJson(value.toString());
                return fixValue(signature, newValue);
            }
            throw new IllegalArgumentException(String.format("Unexpected type found: %s", value.getClass()));
        }
        if (signature.getBase().equals(MAP)) {
            if (Map.class.isAssignableFrom(value.getClass())) {
                TypeSignature keySignature = signature.getTypeOrNamedTypeParametersAsTypeSignatures().get(0);
                TypeSignature valueSignature = signature.getTypeOrNamedTypeParametersAsTypeSignatures().get(1);
                Map<Object, Object> fixedValue = new HashMap<>();
                for (Map.Entry<?, ?> entry : (Set<Map.Entry<?, ?>>) Map.class.cast(value).entrySet()) {
                    fixedValue.put(fixValue(keySignature, entry.getKey()), fixValue(valueSignature, entry.getValue()));
                }
                return fixedValue;
            }
            // JSON keys may be serialized and deserialized as simple strings
            else if (value.getClass() == String.class) {
                Map<String, String> newValue = MAP_JSON_CODEC.fromJson(value.toString());
                return fixValue(signature, newValue);
            }
            throw new IllegalArgumentException(String.format("Unexpected type found: %s", value.getClass()));
        }

View on GitHub (pinned to 55bb57d202)

Solutions

1. Check that the query result type signature and the returned data agree
2. Upgrade client and server to matching versions so new type signatures are recognized
3. Simplify the query to avoid the exotic type if client upgrade is impossible

When it happens

Trigger: Thrown at presto-client/src/main/java/com/facebook/presto/client/FixJsonDataUtils.java:121 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/c82e7ddbbdffa66b. Report an issue: GitHub.