`add_column` changes the values of an existing column for files without field IDs

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@Anurag-S1ngh já está trabalhando nisso.

Desde 10/11/2026.

  • #4332 de @Anurag-S1ngh — aberto

Avaliação

Dificuldade
4/5
Tempo estimado
3-5 dias
Facilidade para iniciantes
57/100
Tipo de issue
Bug
Clareza
Razoavelmente clara
Status de atividade
Ativa
Stack de tecnologia
postgresql, python
Domínio
database

Direção de pesquisa

Start with _remove_reassigned_names in pyiceberg/table/name_mapping.py and trace how schema updates change name mappings for files without field IDs. Reproduce the report using the supplied add_files, rename, and add_column sequence, then check both scan results and IsNull("b") filtering. Done means the existing column keeps its values and the filter returns the matching rows after adding the reused name.

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Descrição

Apache Iceberg version

0.12.0 (latest release); the same logic is on main

Please describe the bug 🐞

Adding a column changes what an existing column reads. Files added with add_files have no field IDs and are read through the name mapping. After a rename, the renamed column reads correctly. Adding a column that reuses the old name then moves that name to the new field in the mapping (_remove_reassigned_names in pyiceberg/table/name_mapping.py). From then on, the renamed column reads as null for those files, and the new column gets its values.

The manifest statistics of those files still describe the original field, so planning also prunes with statistics that no longer match what is read: below, IsNull("b") skips the file although both rows read b as null.

import tempfile

import pyarrow as pa
import pyarrow.parquet as pq
from pyiceberg.catalog.sql import SqlCatalog
from pyiceberg.expressions import IsNull
from pyiceberg.schema import Schema
from pyiceberg.types import LongType, NestedField

d = tempfile.mkdtemp()
catalog = SqlCatalog("c", uri=f"sqlite:///{d}/c.db", warehouse=f"file://{d}")
catalog.create_namespace("ns")
table = catalog.create_table("ns.t", Schema(NestedField(1, "a", LongType())))

# a Parquet file without field IDs, read through the name mapping
pq.write_table(pa.table({"a": [1, 3]}), f"{d}/imported.parquet")
table.add_files([f"file://{d}/imported.parquet"])

with table.update_schema() as update:
    update.rename_column("a", "b")
print(table.scan().to_arrow().to_pydict())
# {'b': [1, 3]}

with table.update_schema() as update:
    update.add_column("a", LongType())
print(table.scan().to_arrow().to_pydict())
# {'b': [None, None], 'a': [1, 3]}: expected {'b': [1, 3], 'a': [None, None]}

print(table.scan(row_filter=IsNull("b")).to_arrow().num_rows)
# 0: the file is pruned by the statistics of `b`, which hold its original values

Expected: adding a column leaves the values of existing columns unchanged, as it does for files with field IDs. The name was written for the original field in those files, so either the mapping keeps it there, or adding a column whose name files without field IDs still use is refused.

Willingness to contribute
  • I can contribute a fix for this bug independently
  • I would be willing to contribute a fix for this bug with guidance from the Iceberg community
  • I cannot contribute a fix for this bug at this time
Linguagem predominante
Python
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Forks
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2d 11h
PRs com merge (30d)
122

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