Relation literal rows are matched to columns by position, so rows with different field names or order produce wrong data

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#6,415 2 comentarios 0 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
70/100
Tipo de issue
Error
Claridad
Bien especificado
Estado de actividad
Activo
Stack tecnológico
rust
Área
compilers

Línea de trabajo

Start at prqlc/prqlc/src/semantic/lowering.rs L377-L414, where pl::ExprKind::Array is lowered into RelationLiteral.columns: columns come from the first row's lineage, and later rows' tuple values are copied in position, ignoring field names. First settle with the maintainers the open design question — reorder each row by name, or reject mismatched rows — plus the rule for unnamed fields like {1, 2}; coordinate with open PR #6413, which edits the same block. Done means from [{a=1, b=2}, {b=3, a=4}] compiles to SQL preserving names, and the other two example shapes either reorder or fail cleanly as decided.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

bug

A relation literal takes its column names from the first row only. Every later row is matched to those columns by position, ignoring its own field names. Queries whose rows disagree compile without error and produce wrong data.

from [{a=1, b=2}, {b=3, a=4}]

compiles (at c945ca81) to

WITH
table_0 AS (
  SELECT
    1 AS a,
    2 AS b
  UNION ALL
  SELECT
    3 AS a,
    4 AS b
)
SELECT
  a,
  b
FROM
  table_0

So the second row comes back as a=3, b=4 rather than a=4, b=3. Two related shapes go wrong the same way:

  • from [{a=1}, {b=2}] yields one column a with values 1, 2. The second row's b is renamed to a.
  • from [{a=1}, {a=2, b=3}] yields only column a. The second row's b=3 is dropped.

The lowering of pl::ExprKind::Array builds RelationLiteral.columns from the expression's lineage, then copies each row's tuple values in order without looking at their names (lowering.rs).

There are two plausible fixes: reorder each row's fields to match the first row's columns by name, or reject rows whose field names differ from the first row's with a compile error. Either way, unnamed fields ({1, 2}) need a rule too: whether they stay positional, and whether mixing named and unnamed fields is allowed. Open PR #6413 changes the same block (it reports malformed rows instead of panicking), so a fix here will probably build on it.

A review of #6413 first spotted this; it isn't caused by that PR.

Lenguaje dominante
Rust
Estrellas
10.9k
Forks
261
Merge medio
3 d 21 h
PR fusionados (30 d)
84

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