Compiled Cypher: a CALL's UNION ALL keeps its null and list marks from the first part only (port of drivine4j#512)

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  • #322 de @jasperblues — fusionado

Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
56/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
python
Área
databases

Línea de trabajo

Start at _called_union in drivine/cypher/sql/sql_cypher_compiler.py, especially the merge loop around line 1874, and compare how it combines marks across UNION ALL parts. Port the named cases from CypherQueryCrossEngineTest.kt and the two steps from spec v0.20.0. Done means the null and list marks merge as described and the regression cases match the expected Neo4j behavior.

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

Descripción

bug

Port of liberation-data/drivine4j#512 (fixed by liberation-data/drivine4j#514). This adds to the note already in #314.

What happens here now: _called_union (drivine/cypher/sql/sql_cypher_compiler.py:1834, merge loop at ~1874) builds each merged column with dataclasses.replace(projected[0]'s value, …). It recomputes only row_keys, from_list, temporal, items, item_items, temporals, text, texts and known across the parts. Every other mark comes from the first part only: JSON's-null (#314's note), and the marks for a list, a list of lists, and a flat list. So when parts differ in kind, the merged column sorts and compares by the first part's kind.

drivine4j's wrong rows before its fix:

  • CALL { RETURN [10] AS v UNION ALL RETURN 10 AS v } RETURN v ORDER BY v gave [10, [10]]; Neo4j gives [[10], 10].
  • v < 2 over [1] ∪ 1 gave [null, null]; Neo4j gives [null, true].
  • v = [1] and v IN [[1], 1] over [1] ∪ [null] gave [true, false]; Neo4j gives [true, null].
  • UNWIND v over [[1]] ∪ [1], then ORDER BY, gave [1, [1]]; Neo4j gives [[1], 1].
  • CALL { RETURN {}.a AS v UNION ALL RETURN [null][0] AS v } RETURN DISTINCT v gave two nulls; Neo4j gives one.

What the fix does: in calledUnion, the JSON's-null mark is set if any part has it. The list, list-of-lists and flat marks are kept only where every part has them, like text/texts.

Tests to port:

  • drivine4j CypherQueryCrossEngineTest.kt: "a CALL's UNION ALL whose later part gives a list's null keeps it one null with a missing key", and "a CALL's UNION ALL whose first part gives a list and a later one a number or a map sorts each by its kind". The second skips Postgres (#307 there) and compares rows without ORDER BY as a multiset.
  • Spec v0.20.0 (drivine-cypher-spec #45): two steps in "A null in a map and a missing key are one null".
Lenguaje dominante
Python
Estrellas
1
Forks
0
Merge medio
1 h 32 min
PR fusionados (30 d)
149

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