REGR: revert behaviour change for concat with empty/all-NaN data

pandas/core/dtypes/missing.py

@@ -18,6 +18,7 @@
 import pandas._libs.missing as libmissing
 from pandas._libs.tslibs import (
     NaT,
+    Period,
     iNaT,
 )
 
@@ -739,3 +740,40 @@ def is_valid_na_for_dtype(obj, dtype: DtypeObj) -> bool:
 
     # fallback, default to allowing NaN, None, NA, NaT
     return not isinstance(obj, (np.datetime64, np.timedelta64, Decimal))
+
+
+def isna_all(arr: ArrayLike) -> bool:
+    """
+    Optimized equivalent to isna(arr).all()
+    """
+    total_len = len(arr)
+
+    # Usually it's enough to check but a small fraction of values to see if
+    #  a block is NOT null, chunks should help in such cases.
+    #  parameters 1000 and 40 were chosen arbitrarily
+    chunk_len = max(total_len // 40, 1000)
+
+    dtype = arr.dtype
+    if dtype.kind == "f":
+        checker = nan_checker
+
+    elif dtype.kind in ["m", "M"] or dtype.type is Period:
+        # error: Incompatible types in assignment (expression has type
+        # "Callable[[Any], Any]", variable has type "ufunc")
+        checker = lambda x: np.asarray(x.view("i8")) == iNaT  # type: ignore[assignment]
+
+    else:
+        # error: Incompatible types in assignment (expression has type "Callable[[Any],
+        # Any]", variable has type "ufunc")
+        checker = lambda x: _isna_array(  # type: ignore[assignment]
+            x, inf_as_na=INF_AS_NA
+        )
+
+    return all(
+        # error: Argument 1 to "__call__" of "ufunc" has incompatible type
+        # "Union[ExtensionArray, Any]"; expected "Union[Union[int, float, complex, str,
+        # bytes, generic], Sequence[Union[int, float, complex, str, bytes, generic]],
+        # Sequence[Sequence[Any]], _SupportsArray]"
+        checker(arr[i : i + chunk_len]).all()  # type: ignore[arg-type]
+        for i in range(0, total_len, chunk_len)
+    )