Raise in P2P if column dtype is wrong

distributed/shuffle/_shuffle.py

@@ -104,9 +104,15 @@ def rearrange_by_column_p2p(
     column: str,
     npartitions: int | None = None,
 ) -> DataFrame:
+    import pandas as pd
+
     from dask.dataframe.core import new_dd_object
 
     meta = df._meta
+    if not pd.api.types.is_integer_dtype(meta[column].dtype):
+        raise TypeError(
+            f"Expected meta {column=} to be an integer column, is {meta[column].dtype}."
+        )
     check_dtype_support(meta)
     npartitions = npartitions or df.npartitions
     token = tokenize(df, column, npartitions)

distributed/shuffle/tests/test_shuffle.py

@@ -2165,3 +2165,45 @@ async def test_set_index_p2p(c, s, *workers):
     await c.close()
     await asyncio.gather(*[check_worker_cleanup(w) for w in workers])
     await check_scheduler_cleanup(s)
+
+
+def test_shuffle_p2p_with_existing_index(client):
+    df = pd.DataFrame({"a": np.random.randint(0, 3, 20)}, index=np.random.random(20))
+    ddf = dd.from_pandas(
+        df,
+        npartitions=4,
+    )
+    ddf = ddf.shuffle("a", shuffle="p2p")
+    result = client.compute(ddf, sync=True)
+    dd.assert_eq(result, df)
+
+
+def test_set_index_p2p_with_existing_index(client):
+    df = pd.DataFrame({"a": np.random.randint(0, 3, 20)}, index=np.random.random(20))
+    ddf = dd.from_pandas(
+        df,
+        npartitions=4,
+    )
+    ddf = ddf.set_index("a", shuffle="p2p")
+    result = client.compute(ddf, sync=True)
+    dd.assert_eq(result, df.set_index("a"))
+
+
+def test_sort_values_p2p_with_existing_divisions(client):
+    "Regression test for #8165"
+    df = pd.DataFrame(
+        {"a": np.random.randint(0, 3, 20), "b": np.random.randint(0, 3, 20)}
+    )
+    ddf = dd.from_pandas(
+        df,
+        npartitions=4,
+    )
+    with dask.config.set({"dataframe.shuffle.method": "p2p"}):
+        ddf = ddf.set_index("a").sort_values("b")
+        result = client.compute(ddf, sync=True)
+        dd.assert_eq(
+            result,
+            df.set_index("a").sort_values("b"),
+            check_index=False,
+            sort_results=False,
+        )