prestodb/presto · error · PrestoException

INVALID_FUNCTION_ARGUMENT

INVALID_FUNCTION_ARGUMENT

Error message

In differential_entropy UDF, max samples must be positive: %s

What it means

The unweighted reservoir-sampling strategy of differential_entropy requires the max_samples parameter to be strictly positive. The constructor validates this before creating the reservoir sample; a zero or negative value would make sampling impossible, so Presto throws INVALID_FUNCTION_ARGUMENT at aggregation setup.

Source

Thrown at presto-main-base/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/UnweightedReservoirSampleStateStrategy.java:33

import com.facebook.presto.spi.PrestoException;
import io.airlift.slice.SliceInput;
import io.airlift.slice.SliceOutput;

import static com.facebook.presto.operator.aggregation.differentialentropy.EntropyCalculations.calculateFromSamplesUsingVasicek;
import static com.facebook.presto.spi.StandardErrorCode.INVALID_FUNCTION_ARGUMENT;
import static java.lang.Math.toIntExact;
import static java.lang.String.format;

public class UnweightedReservoirSampleStateStrategy
        implements DifferentialEntropyStateStrategy
{
    private final UnweightedDoubleReservoirSample reservoir;

    public UnweightedReservoirSampleStateStrategy(long maxSamples)
    {
        if (maxSamples <= 0) {
            throw new PrestoException(
                    INVALID_FUNCTION_ARGUMENT,
                    format("In differential_entropy UDF, max samples must be positive: %s", maxSamples));
        }
        if (maxSamples >= UnweightedDoubleReservoirSample.MAX_SAMPLES_LIMIT) {
            throw new PrestoException(
                    INVALID_FUNCTION_ARGUMENT,
                    format("In differential_entropy UDF, max samples  must be capped: max_samples=%s, cap=%s", maxSamples, UnweightedDoubleReservoirSample.MAX_SAMPLES_LIMIT));
        }

        reservoir = new UnweightedDoubleReservoirSample(toIntExact(maxSamples));
    }

    private UnweightedReservoirSampleStateStrategy(UnweightedReservoirSampleStateStrategy other)
    {
        reservoir = other.reservoir.clone();
    }

    private UnweightedReservoirSampleStateStrategy(UnweightedDoubleReservoirSample reservoir)

View on GitHub (pinned to 55bb57d202)

Solutions

1. Pass a positive integer literal for max_samples (a few thousand is typical)
2. Check any bound application parameter for 0 or negative defaults and correct it
3. Validate inputs before the query: WHERE :max_samples > 0 or application-side checks
4. Use a constant rather than a per-row expression that can be <= 0

Example fix

-- before
SELECT differential_entropy(x, 1.0, :max_samples) FROM t; -- :max_samples = 0
-- after
SELECT differential_entropy(x, 1.0, 10000) FROM t;

-- max_samples must be > 0
SELECT :max_samples > 0 AS valid; -- or application-side assert maxSamples > 0

boolean isValidMaxSamples(long maxSamples) { return maxSamples > 0; }

When it happens

Trigger: Calling differential_entropy(x, 1.0, max_samples) where max_samples is a literal 0, a negative number, or a non-constant expression that evaluates to <= 0 for some group.

Common situations: Parameterized queries where an application passes 0 as a default/placeholder; sign errors in computed values; using a column that is 0 for some rows as max_samples in a grouped query.

Related errors

• array1 and array2 cannot be null and should have same length
• arrayOffset is negative
• positionCount is negative
• positionCount is negative
• ids length is less than positionCount

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/4708bbd8db1deb2c. Report an issue: GitHub.