Overaggressive pruning of nested fields(?) breaks some valid queries unless parquet pushdown is disabled

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@ianthetechie y travaille déjà.

Depuis le 9/11/2026.

  • #27259 par @ianthetechie — ouverte

Évaluation

Difficulté
4/5
Temps estimé
3-5 jours
Accessibilité débutants
35/100
Type d'issue
Bug
Clarté
Plutôt claire
Activité
À l'abandon
Stack technique
rust, sql
Domaine
backend, databases

Piste de recherche

Start with the parquet reproducer in the issue and compare behavior with both pushdown settings enabled and disabled; the regression is reported between DataFusion 53.1.0 and 54.0.0. Trace nested field pruning and predicate pushdown to find why names.common is unavailable while evaluating the filter, then add a regression test for the original query. The issue links open pull request #27259, so check its status and discussion before taking this on.

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

Description

bug
Describe the bug

Valid queries against a parquet table with certain structural characteristics now fail with an execution error: Field common not found in struct.

As noted in the issue title, my guess is that this is due to overaggressive pruning of nested fields during pushdown, but that needs some further verification.

I have worked up a minimal reproducer (below) which you can replicate with the datafusion-cli.

To Reproduce
-- Set up: an external parquet table with a few rows.
-- Apologies for the somewhat oblique construction, but certain DataFusion versions
-- rejected a simpler version with map(['en'], [english]).
COPY (
    SELECT named_struct(
        'primary', local_name,
        'common', map([language], [english])
    ) AS names
    FROM (VALUES ('Local', 'en', 'English'), (NULL, 'en', 'Fallback'), ('', 'en', ''))
        AS input(local_name, language, english)
) TO '/tmp/datafusion-reproducer.parquet' STORED AS PARQUET;

CREATE EXTERNAL TABLE nested_names
STORED AS PARQUET
LOCATION '/tmp/datafusion-reproducer.parquet';

-- These are defaults for a while AFAIK but including for reproducibility.
SET datafusion.execution.parquet.pushdown_filters = true;
SET datafusion.optimizer.enable_leaf_expression_pushdown = true;

-- Expected:
-- +-----------------------------+
-- | nested_names.names[primary] |
-- +-----------------------------+
-- | Local                       |
-- | NULL                        |
-- +-----------------------------+
--
-- Actual:
-- Parquet error: External: External error: Error evaluating filter predicate
-- caused by
-- Execution error: Field common not found in struct
SELECT names.primary
FROM nested_names
WHERE coalesce(names.primary, names.common['en']) <> '';

SET datafusion.execution.parquet.pushdown_filters = false;
SET datafusion.optimizer.enable_leaf_expression_pushdown = false;

-- With BOTH of these settings disabled, it succeeds and returns Local and NULL.
-- It still fails if either one is true.
SELECT names.primary
FROM nested_names
WHERE coalesce(names.primary, names.common['en']) <> '';

-- Hacky SQL workaround: succeeds even with pushdown enabled.
SET datafusion.execution.parquet.pushdown_filters = true;
SET datafusion.optimizer.enable_leaf_expression_pushdown = true;

SELECT names.primary
FROM nested_names
WHERE coalesce(names.primary, map_extract(names.common, 'en')[1]) <> '';
Expected behavior

The original query should succeed as written with syntax like names.common['en'], without needing to disable predicate pushdown or SQL-level hacks.

Additional context

I haven't had a chance to do a full git bisect, but installing a few releases, I've narrowed it quite a bit. Release-wise, the bug first appeared in 54.0.0; 53.1.0 was fine, and it is still broken on main at the time of this writing.

Willingness to contribute

I would like to contribute a fix for this bug, but request guidance from the DataFusion community

Langage dominant
Rust
Étoiles
9.6k
Forks
2.6k
Merge moyen
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PR mergées (30 j)
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