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create_branch and create_tag replace an existing ref of the same name #4187
Description
Apache Iceberg version
0.12.0 (latest release)
Please describe the bug 🐞
Currently, create_branch and create_tag set the ref without checking whether it exists, so an existing branch is reset and loses its commits, and a tag moves. Java refuses an existing name with Ref dev already exists.
import tempfile
import pyarrow as pa
from pyiceberg.catalog.sql import SqlCatalog
cat = SqlCatalog("c", uri="sqlite:///:memory:", warehouse=f"file://{tempfile.mkdtemp()}")
cat.create_namespace("ns")
t = cat.create_table("ns.t", schema=pa.schema([("x", pa.int64())]))
t.append(pa.table({"x": [1]}))
s1 = t.current_snapshot().snapshot_id
t.manage_snapshots().create_branch(s1, "dev").create_tag(s1, "v1").commit()
t.append(pa.table({"x": [2]}), branch="dev")
t.append(pa.table({"x": [3]}))
t.manage_snapshots().create_branch(s1, "dev").commit()
print(t.scan().use_ref("dev").to_arrow()["x"].to_pylist())
# [1], should raise; the commit holding 2 is now on no ref
t.manage_snapshots().create_tag(t.current_snapshot().snapshot_id, "v1").commit()
print(sorted(t.scan().use_ref("v1").to_arrow()["x"].to_pylist()))
# [1, 3], should raise and leave v1 at [1]remove_branch and remove_tag check nothing either: remove_branch("main") is accepted and the table then reads as empty.
tested on pyiceberg 0.12.0 and main
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
Activity
tanmayrauth commentedon Oct 30, 2026
Can I work on this?
deepdave98 commentedon Nov 9, 2026
I have a fix for this ready:
create_branchandcreate_tagnow raiseValueError("Ref x already exists")when the name is taken, including by an earlier operation in the same chain, andremove_branch/remove_tagraise for a missing name, for the wrong kind of ref, and formain, with the same messages as Java'sUpdateSnapshotReferencesOperation. Unit tests cover each case and the script in this issue now raises on both re-creates. Opening the PR now; @tanmayrauth, if you already have a branch for this, say so and I will defer to it.Reject existing ref names in create_branch and create_tag (apache#4319)