prestodb/presto · error · PrestoException

NOT_SUPPORTED

NOT_SUPPORTED

Error message

Cannot operate on a t-digest with real numbers

What it means

The t-digest implementation only accepts DOUBLE input values. REAL (float) is explicitly rejected with NOT_SUPPORTED rather than silently upcast, because the underlying TDigest method handles are bound only for double.

Source

Thrown at presto-main-base/src/main/java/com/facebook/presto/operator/aggregation/StatisticalDigestAggregationFunction.java:204

        switch (type) {
            case TDIGEST:
                return getTDigestInputMethodHandle(valueType, arity);
            case QDIGEST:
                return getQuantileDigestInputMethodHandle(valueType, arity);
            default:
                throw new PrestoException(INVALID_FUNCTION_ARGUMENT, format("%s must be a statistical digest", type));
        }
    }

    private MethodHandle getTDigestInputMethodHandle(Type valueType, int arity)
    {
        final MethodHandle inputFunction;
        switch (valueType.getDisplayName()) {
            case StandardTypes.DOUBLE:
                inputFunction = T_DIGEST_INPUT_DOUBLE;
                break;
            case StandardTypes.REAL:
                throw new PrestoException(NOT_SUPPORTED, "Cannot operate on a t-digest with real numbers");
            case StandardTypes.BIGINT:
                throw new PrestoException(NOT_SUPPORTED, "Cannot operate on a t-digest with longs");
            default:
                throw new PrestoException(INVALID_FUNCTION_ARGUMENT, format("Unsupported type %s supplied", valueType.getDisplayName()));
        }
        return addArguments(inputFunction, arity, DEFAULT_COMPRESSION);
    }

    private static MethodHandle getQuantileDigestInputMethodHandle(Type valueType, int arity)
    {
        final MethodHandle inputFunction;
        switch (valueType.getDisplayName()) {
            case StandardTypes.DOUBLE:
                inputFunction = QUANTILE_DIGEST_INPUT_DOUBLE;
                break;
            case StandardTypes.REAL:
                inputFunction = INPUT_REAL;
                break;

View on GitHub (pinned to 55bb57d202)

Solutions

1. CAST the REAL column to DOUBLE before the t-digest aggregation.
2. Use a q-digest/double aggregation variant that supports REAL if available.
3. Change the schema to store DOUBLE if t-digest operations are the primary use.

Example fix

// before
SELECT tdigest_agg(temperature) FROM sensors; -- temperature is REAL
// after
SELECT tdigest_agg(CAST(temperature AS DOUBLE)) FROM sensors;

-- verify column type before t-digest
SELECT typeof(temperature) FROM sensors LIMIT 1; -- must be double, not real

boolean supportsTDigest(Type t) { return t.getDisplayName().equals("double"); }

try { agg(); } catch (PrestoException e) { if (e.getErrorCode().getName().equals("NOT_SUPPORTED") && e.getMessage().contains("real")) { castToDoubleAndRetry(); } else throw e; }

When it happens

Trigger: Creating a t-digest aggregation (tdigest_agg or similar) over a REAL column, which reaches getTDigestInputMethodHandle's REAL case.

Common situations: Using float4 columns (e.g. sensor readings) directly with t-digest quantile approximations.

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

• NOT_SUPPORTED
• NOT_SUPPORTED
• BIGQUERY_UNSUPPORTED_COLUMN_TYPE
• NOT_SUPPORTED
• Unsupported Cassandra type: %s

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/99b96c0676e491fa. Report an issue: GitHub.