Should `append` sometimes or always create `UNION ALL BY NAME`?

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Nadie ha tomado este issue todavía.

  • #6037 de @kgutwin — cerrado sin fusionar

Evaluación

Dificultad
5/5
Tiempo estimado
Más de una semana
Aptitud para principiantes
25/100
Tipo de issue
Nueva funcionalidad
Claridad
Bastante claro
Estado de actividad
Estancado
Stack tecnológico
rust, sql
Área
backend, databases

Línea de trabajo

Read the compiler handling for the PRQL append transform and the linked issues #4724, #2680, and #3184 to understand current behavior and compatibility concerns. The issue asks whether append should use name-based unions by default or expose a mode for name versus position; it does not identify files or tests. Done means a decision on the semantics and, if chosen, implementation and tests covering the selected behavior.

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

Descripción

needs-discussion
What's up?

Currently a PRQL append transform will result in UNION ALL:

from tbl_a
append tbl_b

gives

SELECT * FROM tbl_a UNION ALL SELECT * FROM tbl_b -- Generated by PRQL compiler version:0.13.3-39-ge393ab4d (https://prql-lang.org)

However, this results in issues like #4724, #2680, and #3184, where the underlying cause is that UNION ALL is interpreted by the database as "unify by column position" rather than "unify by column name". See the DuckDB docs:

Traditional set operations unify queries by column position, and require the to-be-combined queries to have the same number of input columns. If the columns are not of the same type, casts may be added. The result will use the column names from the first query.
DuckDB also supports UNION [ALL] BY NAME, which joins columns by name instead of by position. UNION BY NAME does not require the inputs to have the same number of columns. NULL values will be added in case of missing columns.

Questions:

  1. Should append always behave as UNION ALL BY NAME to simplify semantics from the user perspective, and also make the compiler's job easier? This would resolve all of the linked issues above without needing to dive into compiler details, but would be a breaking change for users expecting traditional UNION ALL behavior.
  2. If "no" to the above question, can we add a by:name or by:position argument to append to allow users to use UNION ALL BY NAME when that makes sense for their use case?
Lenguaje dominante
Rust
Estrellas
10.9k
Forks
261
Merge medio
3 d 21 h
PR fusionados (30 d)
84

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