[lake/iceberg] Support MAP type in Iceberg tables

[pithecuse527]

Purpose

Linked issue: #2258

Brief change log

Tests

API and Format

Documentation

[Copilot]

Pull request overview

This pull request adds support for MAP data types in Iceberg tables for Fluss, addressing issue #2258. The implementation enables conversion of Fluss MAP types to Iceberg MapType and provides runtime support for reading and writing map data.

Changes:

• Implemented MAP type conversion from Fluss to Iceberg format in FlussDataTypeToIcebergDataType
• Added FlussMapAsIcebergMap adapter class for converting Fluss InternalMap to Java Map for Iceberg
• Enhanced FlussArrayAsIcebergList and FlussRowAsIcebergRecord to support nested MAP types
• Added FLOAT and DOUBLE support to IcebergBinaryRowWriter.createFieldWriter
• Added explicit error handling for MAP and ARRAY types in bucket key writer
• Comprehensive test coverage for MAP type conversions, including nested structures

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
FlussDataTypeToIcebergDataType.java	Replaced UnsupportedOperationException with actual MAP type conversion logic, handling field ID allocation
FlussMapAsIcebergMap.java	New adapter class for converting Fluss InternalMap to Java Map, with support for all scalar types and nested collections
FlussRowAsIcebergRecord.java	Added MAP type handling in field converter creation
FlussArrayAsIcebergList.java	Added support for MAP elements within arrays
IcebergBinaryRowWriter.java	Added FLOAT/DOUBLE type support and explicit error messages for non-scalar bucket key types
FlussDataTypeToIcebergDataTypeMapTest.java	New comprehensive test suite covering MAP type conversions with various key-value type combinations
FlussRowAsIcebergRecordTest.java	Added integration tests for MAP data conversion including nested structures
IcebergBinaryRowWriterTest.java	Added tests to verify MAP and ARRAY types are properly rejected as bucket keys

Comments suppressed due to low confidence (1)

fluss-lake/fluss-lake-iceberg/src/main/java/org/apache/fluss/lake/iceberg/source/FlussArrayAsIcebergList.java:118

• The get method is missing support for RowType, which is a supported nested type in Arrays. When an Array contains Row values (e.g., Array<Row<id: Int, name: String>>), this method will throw an UnsupportedOperationException. Add a case to handle RowType by retrieving the InternalRow from the array and converting it appropriately, similar to how it's done in FlussRowAsIcebergRecord.createTypeConverter.

    public Object get(int index) {
        if (flussArray.isNullAt(index)) {
            return null;
        }

        if (elementType instanceof BooleanType) {
            return flussArray.getBoolean(index);
        } else if (elementType instanceof TinyIntType) {
            return (int) flussArray.getByte(index);
        } else if (elementType instanceof SmallIntType) {
            return (int) flussArray.getShort(index);
        } else if (elementType instanceof IntType) {
            return flussArray.getInt(index);
        } else if (elementType instanceof BigIntType) {
            return flussArray.getLong(index);
        } else if (elementType instanceof FloatType) {
            return flussArray.getFloat(index);
        } else if (elementType instanceof DoubleType) {
            return flussArray.getDouble(index);
        } else if (elementType instanceof StringType) {
            return flussArray.getString(index).toString();
        } else if (elementType instanceof CharType) {
            CharType charType = (CharType) elementType;
            return flussArray.getChar(index, charType.getLength()).toString();
        } else if (elementType instanceof BytesType || elementType instanceof BinaryType) {
            return ByteBuffer.wrap(flussArray.getBytes(index));
        } else if (elementType instanceof DecimalType) {
            DecimalType decimalType = (DecimalType) elementType;
            return flussArray
                    .getDecimal(index, decimalType.getPrecision(), decimalType.getScale())
                    .toBigDecimal();
        } else if (elementType instanceof LocalZonedTimestampType) {
            LocalZonedTimestampType ltzType = (LocalZonedTimestampType) elementType;
            return toIcebergTimestampLtz(
                    flussArray.getTimestampLtz(index, ltzType.getPrecision()).toInstant());
        } else if (elementType instanceof TimestampType) {
            TimestampType tsType = (TimestampType) elementType;
            return flussArray.getTimestampNtz(index, tsType.getPrecision()).toLocalDateTime();
        } else if (elementType instanceof DateType) {
            return DateTimeUtils.toLocalDate(flussArray.getInt(index));
        } else if (elementType instanceof TimeType) {
            return DateTimeUtils.toLocalTime(flussArray.getInt(index));
        } else if (elementType instanceof ArrayType) {
            InternalArray innerArray = flussArray.getArray(index);
            return innerArray == null
                    ? null
                    : new FlussArrayAsIcebergList(
                            innerArray, ((ArrayType) elementType).getElementType());
        } else if (elementType instanceof MapType) {
            MapType mapType = (MapType) elementType;
            InternalMap internalMap = flussArray.getMap(index);
            return new FlussMapAsIcebergMap(
                    internalMap, mapType.getKeyType(), mapType.getValueType());
        } else {
            throw new UnsupportedOperationException(
                    "Unsupported array element type conversion for Fluss type: "
                            + elementType.getClass().getSimpleName());
        }

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[pithecuse527]

All issues raised by Copilot have been resolved.
Fixed missing Iceberg data structures (such as RowType) and corrected the faulty consecutive ID logic caused by recursion.

@luoyuxia
Any chance you could review this PR? Thank you.

[luoyuxia]

@MehulBatra Could you please help review this pr?

[MehulBatra]

Already in my radar, Will try to review by EOD! @pithecuse527 @luoyuxia

[MehulBatra]

@pithecuse527 can you run mvn spotless:apply and trying running tests locally to check if all CI pass, then push it again.

[pithecuse527]

@MehulBatra
solved the spotless issue and pushed again

[luoyuxia]

@pithecuse527 Thanks for the pr. I left some comments. PTAL.
Also, please don't forget to add IT in FlinkUnionReadLogTableITCase. Refer to pr #2278

[pithecuse527]

@luoyuxia

I've added the integration test for iceberg map in FlinkUnionReadLogTableITCase

[luoyuxia]

@pithecuse527 Thanks for the pr. LGTM overall. Left minor comments.

[luoyuxia]

@pithecuse527 Thanks for the pr. LGTM!

[luoyuxia]

@pithecuse527 But the ci still fails. Also could you please also update the doc for map type mapping?
https://fluss.apache.org/docs/next/streaming-lakehouse/integrate-data-lakes/iceberg/#data-type-mapping