prestodb/presto · error · PrestoException

GENERIC_INTERNAL_ERROR

GENERIC_INTERNAL_ERROR

Error message

Expected row value field count does not match type field count

What it means

MongoDB sink conversion error while writing a ROW-typed value: the number of fields in the incoming row block does not match the field count of the declared row type. This indicates a schema mismatch between the query's row type and the connector's expectation during INSERT.

Source

Thrown at presto-mongodb/src/main/java/com/facebook/presto/mongodb/MongoPageSink.java:225

            Block mapBlock = block.getBlock(position);

            // map type is converted into list of fixed keys document
            List<Object> values = new ArrayList<>(mapBlock.getPositionCount() / 2);
            for (int i = 0; i < mapBlock.getPositionCount(); i += 2) {
                Map<String, Object> mapValue = new HashMap<>();
                mapValue.put("key", getObjectValue(keyType, mapBlock, i));
                mapValue.put("value", getObjectValue(valueType, mapBlock, i + 1));
                values.add(mapValue);
            }

            return unmodifiableList(values);
        }
        if (isRowType(type)) {
            Block rowBlock = block.getBlock(position);

            List<Type> fieldTypes = type.getTypeParameters();
            if (fieldTypes.size() != rowBlock.getPositionCount()) {
                throw new PrestoException(StandardErrorCode.GENERIC_INTERNAL_ERROR, "Expected row value field count does not match type field count");
            }

            if (isImplicitRowType(type)) {
                List<Object> rowValue = new ArrayList<>();
                for (int i = 0; i < rowBlock.getPositionCount(); i++) {
                    Object element = getObjectValue(fieldTypes.get(i), rowBlock, i);
                    rowValue.add(element);
                }
                return unmodifiableList(rowValue);
            }

            Map<String, Object> rowValue = new HashMap<>();
            for (int i = 0; i < rowBlock.getPositionCount(); i++) {
                rowValue.put(
                        type.getTypeSignature().getParameters().get(i).getNamedTypeSignature().getName().orElse("field" + i),
                        getObjectValue(fieldTypes.get(i), rowBlock, i));
            }
            return unmodifiableMap(rowValue);

View on GitHub (pinned to 55bb57d202)

Solutions

1. Align the inserted row type field count with the target schema
2. Recreate the MongoDB table definition to match the row type
3. Cast the value to the exact ROW(...) shape before inserting

When it happens

Trigger: Thrown at presto-mongodb/src/main/java/com/facebook/presto/mongodb/MongoPageSink.java:225 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/451d866450accbf3. Report an issue: GitHub.