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Unknown type names inside a container decode silently as wrong data

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#589 0 commentaires 0 réactions 0 personnes assignées Voir sur GitHub

Les mainteneurs répondent en général sous 1 jour

@Hakaou y travaille déjà.

Depuis le 18/10/2026.

  • #590 par @Hakaou — ouverte

Évaluation

Difficulté
4/5
Temps estimé
1-2 jours
Accessibilité débutants
48/100
Type d'issue
Bug
Clarté
Plutôt claire
Activité
Active
Stack technique
clickhouse, cpp
Domaine
backend, databases

Piste de recherche

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.

Rédigé par le modèle d'indexation à partir du texte de l'issue.

Description

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.

Langage dominant
C
Étoiles
385
Forks
211
Merge moyen
18 h 22 min
PR mergées (30 j)
4

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