client-v2: geo columns (Point/Ring/Polygon/...) are misread in the Native format

Start in client-v2/src/main/java/com/clickhouse/client/api/data_formats/NativeFormatReader.java, especially readBlock(), and compare its columnar handling with BinaryStreamReader’s geo decoders. Run the supplied numbers(3) Native reproduction and compare it with RowBinaryWithNamesAndTypes, including a fixed-width column after the geo column. Done means geo values match the server without desynchronization, or Native rejects unsupported geo types with a clear error.

Description

client-v2 cannot read geo columns (Point, Ring, LineString, MultiLineString, Polygon, MultiPolygon) from the Native format. The same queries read correctly with RowBinaryWithNamesAndTypes.

Two symptoms, by type:

• Point with more than one row in a block — silent data corruption. The coordinates are returned scrambled across rows. No exception, and a fixed-width column after the geo column still reads correctly, so nothing signals the corruption.
• Ring / LineString / MultiLineString / Polygon / MultiPolygon — the block desynchronizes and the read fails with IllegalArgumentException: Non-empty typeName is required, which does not indicate the cause.

Point with exactly one row per block reads correctly by coincidence (with one row, the columnar and the row-wise layouts are byte-identical).

Steps to reproduce

1. Run a query that selects a geo column with QuerySettings.setFormat(ClickHouseFormat.Native) and read it with client.newBinaryFormatReader(response).
2. For Point, use a query that returns 3 rows in one block; the returned coordinates do not match the server.
3. For Ring (or any other multi-point geo type), the read throws.

Error Log or Exception StackTrace

java.lang.IllegalArgumentException: Non-empty typeName is required
	at com.clickhouse.data.ClickHouseColumn.of(ClickHouseColumn.java:...)
	at com.clickhouse.client.api.data_formats.NativeFormatReader.readBlock(NativeFormatReader.java:87)

The exception is a consequence of the desync: after the geo column is read with the wrong layout, the stream position is inside the payload, so the next column header is parsed as an empty name/type.

Expected Behaviour

The Native format must return the same values as RowBinaryWithNamesAndTypes, which agrees with the server.

Server (ClickHouse 26.7.3.19), FORMAT JSONCompactEachRow:

[0, [1,2], 42]
[1, [3,4], 42]
[2, [5,6], 42]

RowBinaryWithNamesAndTypes (correct):

row 0: rowId=0 g=[1.0, 2.0] tail=42
row 1: rowId=1 g=[3.0, 4.0] tail=42
row 2: rowId=2 g=[5.0, 6.0] tail=42

Native (actual — coordinates scrambled, no error):

row 0: rowId=0 g=[1.0, 3.0] tail=42
row 1: rowId=1 g=[5.0, 2.0] tail=42
row 2: rowId=2 g=[4.0, 6.0] tail=42

Ring, same shape, Native (actual):

EXCEPTION: java.lang.IllegalArgumentException: Non-empty typeName is required

while RowBinaryWithNamesAndTypes returns the correct [[1.0,2.0],[3.0,4.0]], [[11.0,12.0],[13.0,14.0]], [[21.0,22.0],[23.0,24.0]].

Root cause

NativeFormatReader.readBlock() (client-v2/src/main/java/com/clickhouse/client/api/data_formats/NativeFormatReader.java:109) enters its columnar branch only when column.isArray() is true. The concrete geo types are their own ClickHouseDataType values, so isArray() is false for all of them and they fall through to the else branch at line 118, which calls binaryStreamReader.readValue(column) once per row. That dispatches to the RowBinary geo decoders — readGeoPoint() (BinaryStreamReader.java:1123), readGeoRing() (:1132), readGeoPolygon() (:1147), readGeoMultiPolygon() (:1161).

The two encodings are not interchangeable:

• Point is Tuple(Float64, Float64). Native writes it column-major — all x values, then all y values. readGeoPoint() reads two adjacent doubles as one point. The byte count per block is the same either way, so the column boundary is preserved and the error stays silent; only the pairing is wrong.
• Ring / LineString are Array(Point). Native writes cumulative UInt64 offsets, then the element tuple column-major. readGeoRing() reads a per-row varuint count followed by interleaved (x, y) pairs, so the first offset byte is consumed as a point count and everything after that is misaligned. Polygon / MultiPolygon add further offset levels with the same result.

Native bytes for the 3-row Point query above, showing the column-major layout the reader does not expect:

0303 05 726f774964 06 55496e743634                    3 cols, 3 rows, 'rowId' UInt64
  0000000000000000 0100000000000000 0200000000000000   0, 1, 2
01 67 05 506f696e74                                    'g' Point
  000000000000f03f 0000000000000840 0000000000001440   x column: 1, 3, 5
  0000000000000040 0000000000001040 0000000000001840   y column: 2, 4, 6
04 7461696c 05 496e743332  2a000000 2a000000 2a000000  'tail' Int32: 42, 42, 42

Suggested fix

Two options; the second is smaller but is itself a behavior change:

1. Decode geo columns column-major in the Native reader. Route them into the existing columnar path by treating each as its array-of-tuple equivalent (Point → columnar Tuple(Float64, Float64), Ring/LineString/MultiPoint → Array(Point), Polygon/MultiLineString → Array(Ring), MultiPolygon → Array(Polygon)), then assemble the double[] / double[][] / double[][][] / double[][][][] values the RowBinary decoders return today, so the value shape returned to callers does not change.
2. Reject geo columns in the Native format with a clear ClientException pointing at RowBinaryWithNamesAndTypes, matching the precedent already in readBlock for the QBit shapes it does not decode (NativeFormatReader.java:102). This turns silent corruption into a loud, actionable failure, but it removes a read path that currently appears to work for single-row Point.

Whichever is chosen, a regression test should place the geo column in the middle of the schema with a fixed-width column after it and read several rows in one block — a single-row Point passes even with the current code.

Two contrast cases must keep their current behavior: reading these types with RowBinaryWithNamesAndTypes is correct today, and the geo write path is unaffected.

Related

• #2955 / #2956 fix per-row lengths from cumulative offsets inside the isArray() branch. Geo columns never reach that branch, so that fix does not cover them.
• Surfaced by a review comment on #3050 (MultiPoint support): https://github.com/ClickHouse/clickhouse-java/pull/3050#discussion_r3894055614. This defect is pre-existing and independent of that PR, whose only BinaryStreamReader change is one extra case MultiPoint: in the RowBinary switch. MultiPoint shares the Array(Point) layout, so once merged it behaves like Ring here.

Code Example

Client client = new Client.Builder()
        .addEndpoint("http://localhost:8123")
        .setUsername("default").setPassword("")
        .compressServerResponse(false)
        .build();

String sql = "SELECT number AS rowId,"
        + " (toFloat64(number*2+1), toFloat64(number*2+2))::Point AS g,"
        + " toInt32(42) AS tail FROM numbers(3) ORDER BY rowId";

QuerySettings settings = new QuerySettings().setFormat(ClickHouseFormat.Native);
try (QueryResponse response = client.query(sql, settings).get()) {
    ClickHouseBinaryFormatReader reader = client.newBinaryFormatReader(response);
    while (reader.next() != null) {
        System.out.println(Arrays.toString((double[]) reader.readValue("g")));
    }
}
// prints [1.0, 3.0] / [5.0, 2.0] / [4.0, 6.0]
// expected [1.0, 2.0] / [3.0, 4.0] / [5.0, 6.0]

// Replacing Point with ::Ring and the same 3-row shape throws instead:
// java.lang.IllegalArgumentException: Non-empty typeName is required

Affected geo types, verified one by one against the server with both formats:

Type	RowBinaryWithNamesAndTypes	Native
Point, 1 row/block	correct	correct (layouts coincide)
Point, 3 rows/block	correct	wrong values, no error
Ring	correct	throws
LineString	correct	throws
MultiLineString	correct	throws
Polygon	correct	throws
MultiPolygon	correct	throws

Configuration

Environment

• Cloud
• Client version: 0.11.0-rc1 (main at 0b781da1f)
• Language version: OpenJDK 17.0.18
• OS: Ubuntu 24.04 (container)

ClickHouse Server

• ClickHouse Server version: 26.7.3.19
• ClickHouse Server non-default settings, if any: none
• CREATE TABLE statements for tables involved: none — reproduces on a SELECT from numbers()
• Sample data for all these tables: n/a

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Found by automated analysis of the client while working on #3050, and verified against a live ClickHouse server (26.7.3.19) rather than by code inspection: every row above was produced by running both formats through client.newBinaryFormatReader(...) and comparing with the server's own JSONCompactEachRow output.