prestodb/presto · error · PrestoException

NOT_SUPPORTED

NOT_SUPPORTED

Error message

Alter Function is not supported in InMemoryFunctionNamespaceManager

What it means

The InMemoryFunctionNamespaceManager explicitly does not implement alterFunction and always throws NOT_SUPPORTED. The testing-only in-memory manager supports create/list/get only, so any ALTER FUNCTION routed to it is rejected.

Source

Thrown at presto-function-namespace-managers-common/src/main/java/com/facebook/presto/functionNamespace/testing/InMemoryFunctionNamespaceManager.java:86

    {
        checkFunctionLanguageSupported(function);
        SqlFunctionId functionId = function.getFunctionId();
        if (!replace && latestFunctions.containsKey(function.getFunctionId())) {
            throw new PrestoException(GENERIC_USER_ERROR, format("Function '%s' already exists", functionId.getId()));
        }

        SqlInvokedFunction replacedFunction = latestFunctions.get(functionId);
        long version = 1;
        if (replacedFunction != null) {
            version = parseLong(replacedFunction.getRequiredVersion()) + 1;
        }
        latestFunctions.put(functionId, function.withVersion(String.valueOf(version)));
    }

    @Override
    public void alterFunction(QualifiedObjectName functionName, Optional<List<TypeSignature>> parameterTypes, AlterRoutineCharacteristics alterRoutineCharacteristics)
    {
        throw new PrestoException(NOT_SUPPORTED, "Alter Function is not supported in InMemoryFunctionNamespaceManager");
    }

    @Override
    public synchronized void dropFunction(QualifiedObjectName functionName, Optional<List<TypeSignature>> parameterTypes, boolean exists)
    {
        throw new PrestoException(NOT_SUPPORTED, "Drop Function is not supported in InMemoryFunctionNamespaceManager");
    }

    /**
     * likePattern / escape is not used for optimization, returning all functions.
     */
    @Override
    public Collection<SqlInvokedFunction> listFunctions(Optional<String> likePattern, Optional<String> escape)
    {
        return latestFunctions.values();
    }

    @Override

View on GitHub (pinned to 55bb57d202)

Solutions

Avoid ALTER FUNCTION on in-memory-backed catalogs; recreate the function with CREATE OR REPLACE instead.
Use a persistent function namespace manager (e.g. JDBC-backed) if alter semantics are required.
Skip/condition test cases that alter functions when using this manager.

Example fix

// before
ALTER FUNCTION test_ns.fn(x BIGINT) SET LANGUAGE SQL;
// after
CREATE OR REPLACE FUNCTION test_ns.fn(x BIGINT) RETURNS BIGINT LANGUAGE SQL RETURN ...;

Defensive patterns

Strategy: validation

Validate before calling

if (manager instanceof InMemoryFunctionNamespaceManager) {
    throw new UnsupportedOperationException("ALTER FUNCTION not supported on in-memory manager; use CREATE OR REPLACE");
}

Type guard

boolean supportsAlter(FunctionNamespaceManager m) {
    return !(m instanceof InMemoryFunctionNamespaceManager);
}

Try / catch

try {
    manager.alterFunction(name, paramTypes, characteristics);
} catch (PrestoException e) {
    if (e.getErrorCode().equals(NOT_SUPPORTED.toErrorCode())) {
        // recreate the function instead of altering
    }
}

Prevention

Do not run ALTER FUNCTION against catalogs backed by the in-memory test manager.
Prefer CREATE OR REPLACE for mutating function definitions in tests.
Use a persistent namespace manager when testing alter semantics.
Document manager capabilities in test fixtures.

When it happens

Trigger: Calling alterFunction (or running ALTER FUNCTION statements) against a catalog backed by the in-memory function namespace manager, regardless of arguments.

Common situations: Running integration tests that exercise ALTER FUNCTION paths; pointing a dev catalog at the in-memory manager and executing production SQL containing ALTER FUNCTION.

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/77e40ded891f93f4. Report an issue: GitHub.