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Unknown type names inside a container decode silently as wrong data

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Seit 18.10.2026.

  • #590 von @Hakaou — offen

Bewertung

Schwierigkeit
4/5
Geschätzter Aufwand
1-2 Tage
Anfängerfreundlichkeit
48/100
Issue-Typ
Bug
Klarheit
Größtenteils klar
Aktivitätsstatus
Aktiv
Tech-Stack
clickhouse, cpp
Bereich
backend, databases

Rechercherichtung

Read the parser and column factory paths discussed in the issue, especially CreateColumnByType and ValidateAST, then review #575 and the stacked draft #590 for the Nested node and container handling. Add validation so unknown types inside the six supported containers fail with the same unsupported column type error as root types, while preserving Nothing behavior. Verify with the reported Array(Int256) case and the existing container tests; the client should reject it instead of misreading the block.

Vom Indexierungsmodell aus dem Issue-Text verfasst.

Beschreibung

Follow-up to the second point of the suggested fix in #571, which #575 leaves aside: validating the elements of a container, so that an unknown type name fails loudly instead of desynchronising the stream.

A type name the parser does not know becomes a Void terminal. At the root, ValidateAST rejects it and the client throws "unsupported column type". Inside a container nothing checks it: the column is created as ColumnNothing, which reads one byte per row, and the rest of the block is misread without any error.

In the client itself, on master (fc5d98f):

CreateColumnByType("Int256");         // nullptr, the client reports "unsupported column type: Int256"
CreateColumnByType("Array(Int256)");  // a column typed Array(Void), no error

Against ClickHouse 26.11:

SELECT CAST(1, 'Int256') AS wide     -- UnimplementedError: unsupported column type: Int256
SELECT [CAST(1, 'Int256')] AS wide   -- one row, no exception, wrong content

Other names a server sends as is and the parser does not know, checked with toTypeName on 26.11: Variant, Dynamic, BFloat16, UInt256, the Interval* types, LineString, MultiPoint, QBit, AggregateFunction. At the root each of them is an error. Inside a container that accepts it, as Array(Int256) shows, the data is misread without any error. Nothing goes through the same path and only works by accident, one byte per row on both sides, which SELECT [] and SELECT NULL rely on.

#578 handles the neighbouring case, a known name the factory cannot build inside a wrapper, which crashed. This one is about names the parser does not know at all, and the two change different functions.

#590 is a draft for it, stacked on #575 because it needs the Nested node from there. It validates the elements of those six containers, leaves the arguments of every other type alone (JSON settings and typed paths, the function name of SimpleAggregateFunction), and registers Nothing. An unknown name inside a container then makes CreateColumnByType return nullptr, so the client throws the same "unsupported column type" as at the root.

Would you rather have a diagnostic that names the inner type? The tests hold either way.

Vorherrschende Sprache
C
Sterne
385
Forks
211
Ø Merge
18 Std. 22 Min.
Gemergte PRs (30 T.)
4

Entwicklungsumgebung

Dieses Projekt bietet weder Dev-Container noch Dockerfile noch Beitragsleitfaden – die Einrichtung liegt bei Ihnen. Beginnen Sie mit der README; die allgemeinen Schritte stehen in unserem Leitfaden für den ersten Beitrag.

Erste Schritte

  1. Lesen Sie das ganze Issue und danach den Beitragsleitfaden des Projekts.
  2. Schreiben Sie ins Issue, dass Sie es übernehmen — das erspart doppelte Arbeit.
  3. Forken Sie das Repository und arbeiten Sie in einem Branch.
  4. Öffnen Sie einen Pull Request, der die Issue-Nummer nennt.

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