prestodb/presto · error · PrestoException

INVALID_FUNCTION_ARGUMENT

INVALID_FUNCTION_ARGUMENT

Error message

map key cannot be null

What it means

Thrown while building a map literal or map from key/value arrays (createMap): a key position in the key block is null. Presto map keys must be non-null because they are hashed and compared, so a null key aborts construction; the value block may contain nulls, the key block may not.

Source

Thrown at presto-main-base/src/main/java/com/facebook/presto/operator/scalar/MapConstructor.java:167

    @UsedByGeneratedCode
    public static Block createMap(
            MapType mapType,
            Type keyType,
            Type valueType,
            MethodHandle keyBlockEqual,
            MethodHandle keyBlockHashCode,
            MethodHandle keyIndeterminate,
            SqlFunctionProperties properties,
            Block keyBlock,
            Block valueBlock)
    {
        checkCondition(keyBlock.getPositionCount() == valueBlock.getPositionCount(), INVALID_FUNCTION_ARGUMENT, "Key and value arrays must be the same length");
        MapBlockBuilder mapBlockBuilder = (MapBlockBuilder) mapType.createBlockBuilder(null, keyBlock.getPositionCount() * 2);
        BlockBuilder blockBuilder = mapBlockBuilder.beginBlockEntry();

        for (int i = 0; i < keyBlock.getPositionCount(); i++) {
            if (keyBlock.isNull(i)) {
                throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "map key cannot be null");
            }

            if (keyType.getJavaType() == Block.class) {
                // If it's not primitive or string, we need to look for nulls in the block.
                Object keyObject = readNativeValue(mapType.getKeyType(), keyBlock, i);
                try {
                    if ((boolean) keyIndeterminate.invoke(keyObject, false)) {
                        throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "map key cannot be indeterminate: " + mapType.getKeyType().getObjectValue(properties, keyBlock, i));
                    }
                }
                catch (Throwable t) {
                    throw internalError(t);
                }
            }

            keyType.appendTo(keyBlock, i, blockBuilder);
            valueType.appendTo(valueBlock, i, blockBuilder);
        }

View on GitHub (pinned to 55bb57d202)

Solutions

1. Replace null keys, e.g. map_from_entries(filter(...)) with coalesce on the key
2. Filter out entries whose key is null before constructing the map
3. Fix upstream data so key columns are never null

When it happens

Trigger: Thrown at presto-main-base/src/main/java/com/facebook/presto/operator/scalar/MapConstructor.java:167 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/8ce8599d84258564. Report an issue: GitHub.