feat(common): introduce FrozenOrderedDict (#9081)

Continuation of #9068 by adding
`FrozenOrderedDict` which calculates its hash from `tuple(self.items()`
rather than `frozenset(self.items())` and also checks for item order
during equality checks.

Closes #9063.

---------

Co-authored-by: Phillip Cloud <417981+cpcloud@users.noreply.github.com>

ibis/backends/tests/test_client.py

@@ -1608,3 +1608,29 @@ def test_json_to_pyarrow(con):
         if val is not None
     }
     assert result == expected
+
+
+@pytest.mark.notyet(["mssql"], raises=PyODBCProgrammingError)
+@pytest.mark.notyet(
+    ["risingwave", "exasol"],
+    raises=com.UnsupportedOperationError,
+    reason="no temp table support",
+)
+@pytest.mark.notyet(
+    ["impala", "trino"], raises=NotImplementedError, reason="no temp table support"
+)
+@pytest.mark.notyet(
+    ["druid"], raises=NotImplementedError, reason="doesn't support create_table"
+)
+@pytest.mark.notyet(
+    ["flink"], raises=com.IbisError, reason="no persistent temp table support"
+)
+def test_schema_with_caching(alltypes):
+    t1 = alltypes.limit(5).select("bigint_col", "string_col")
+    t2 = alltypes.limit(5).select("string_col", "bigint_col")
+
+    pt1 = t1.cache()
+    pt2 = t2.cache()
+
+    assert pt1.schema() == t1.schema()
+    assert pt2.schema() == t2.schema()

ibis/common/collections.py

@@ -288,7 +288,9 @@ def __hash__(self) -> int:
         return self.__precomputed_hash__
 
     def __setitem__(self, key: K, value: V) -> None:
-        raise TypeError("'FrozenDict' object does not support item assignment")
+        raise TypeError(
+            f"'{self.__class__.__name__}' object does not support item assignment"
+        )
 
     def __setattr__(self, name: str, _: Any) -> None:
         raise TypeError(f"Attribute {name!r} cannot be assigned to frozendict")
@@ -297,6 +299,25 @@ def __reduce__(self) -> tuple:
         return (self.__class__, (dict(self),))
 
 
+@public
+class FrozenOrderedDict(FrozenDict[K, V]):
+    def __init__(self, *args, **kwargs):
+        super(FrozenDict, self).__init__(*args, **kwargs)
+        hashable = tuple(self.items())
+        object.__setattr__(self, "__precomputed_hash__", hash(hashable))
+
+    def __hash__(self) -> int:
+        return self.__precomputed_hash__
+
+    def __eq__(self, other: Any) -> bool:
+        if not isinstance(other, collections.abc.Mapping):
+            return NotImplemented
+        return tuple(self.items()) == tuple(other.items())
+
+    def __ne__(self, other: Any) -> bool:
+        return not self == other
+
+
 class RewindableIterator(Iterator[V]):
     """Iterator that can be rewound to a checkpoint.
 

ibis/common/tests/test_collections.py

@@ -8,6 +8,7 @@
     Collection,
     Container,
     FrozenDict,
+    FrozenOrderedDict,
     Iterable,
     Iterator,
     Mapping,
@@ -429,6 +430,41 @@ def test_frozendict():
     assert_pickle_roundtrip(d)
 
 
+def test_frozenordereddict():
+    d = FrozenOrderedDict({"a": 1, "b": 2, "c": 3})
+    e = FrozenOrderedDict(a=1, b=2, c=3)
+    f = FrozenOrderedDict(a=1, b=2, c=3, d=4)
+    g = FrozenOrderedDict(a=1, c=3, b=2)
+    h = FrozenDict(a=1, b=2, c=3)
+
+    assert isinstance(d, Mapping)
+    assert isinstance(d, collections.abc.Mapping)
+
+    assert d == e
+    assert d != f
+    assert e == h
+    assert h == e
+    assert e != g
+    assert g != e
+    assert g != h
+    assert h != g
+
+    assert d["a"] == 1
+    assert d["b"] == 2
+
+    msg = "'FrozenOrderedDict' object does not support item assignment"
+    with pytest.raises(TypeError, match=msg):
+        d["a"] = 2
+    with pytest.raises(TypeError, match=msg):
+        d["d"] = 4
+
+    assert hash(FrozenOrderedDict(a=1, b=2)) == hash(FrozenOrderedDict(a=1, b=2))
+    assert hash(FrozenOrderedDict(a=1, b=2)) != hash(FrozenOrderedDict(b=2, a=1))
+    assert hash(FrozenOrderedDict(a=1, b=2)) != hash(d)
+
+    assert_pickle_roundtrip(d)
+
+
 def test_rewindable_iterator():
     it = RewindableIterator(range(10))
     assert next(it) == 0

ibis/expr/datatypes/core.py

@@ -14,7 +14,7 @@
 from typing_extensions import Self, get_args, get_origin
 
 from ibis.common.annotations import attribute
-from ibis.common.collections import FrozenDict, MapSet
+from ibis.common.collections import FrozenOrderedDict, MapSet
 from ibis.common.dispatch import lazy_singledispatch
 from ibis.common.grounds import Concrete, Singleton
 from ibis.common.patterns import Coercible, CoercionError
@@ -823,7 +823,7 @@ def _pretty_piece(self) -> str:
 class Struct(Parametric, MapSet):
     """Structured values."""
 
-    fields: FrozenDict[str, DataType]
+    fields: FrozenOrderedDict[str, DataType]
 
     scalar = "StructScalar"
     column = "StructColumn"

ibis/expr/datatypes/tests/test_core.py

@@ -421,6 +421,18 @@ def test_struct_set_operations():
     assert d > c
 
 
+def test_struct_equality():
+    st1 = dt.Struct({"a": dt.int64, "b": dt.string})
+    st2 = dt.Struct({"a": dt.int64, "b": dt.string})
+    st3 = dt.Struct({"b": dt.string, "a": dt.int64})
+    st4 = dt.Struct({"a": dt.int64, "b": dt.string, "c": dt.float64})
+
+    assert st1 == st2
+    assert st1 != st3
+    assert st1 != st4
+    assert st3 != st2
+
+
 def test_singleton_null():
     assert dt.null is dt.Null()
 

ibis/expr/operations/relations.py

@@ -10,7 +10,7 @@
 import ibis.expr.datashape as ds
 import ibis.expr.datatypes as dt
 from ibis.common.annotations import attribute
-from ibis.common.collections import FrozenDict
+from ibis.common.collections import FrozenDict, FrozenOrderedDict
 from ibis.common.exceptions import IbisTypeError, IntegrityError, RelationError
 from ibis.common.grounds import Concrete
 from ibis.common.patterns import Between, InstanceOf
@@ -41,7 +41,7 @@ def __coerce__(cls, value):
 
     @property
     @abstractmethod
-    def values(self) -> FrozenDict[str, Value]:
+    def values(self) -> FrozenOrderedDict[str, Value]:
         """A mapping of column names to expressions which build up the relation.
 
         This attribute is heavily used in rewrites as well as during field
@@ -59,13 +59,13 @@ def schema(self) -> Schema:
         ...
 
     @property
-    def fields(self) -> FrozenDict[str, Column]:
+    def fields(self) -> FrozenOrderedDict[str, Column]:
         """A mapping of column names to fields of the relation.
 
         This calculated property shouldn't be overridden in subclasses since it
         is mostly used for convenience.
         """
-        return FrozenDict({k: Field(self, k) for k in self.schema})
+        return FrozenOrderedDict({k: Field(self, k) for k in self.schema})
 
     def to_expr(self):
         from ibis.expr.types import Table
@@ -110,7 +110,7 @@ def _check_integrity(values, allowed_parents):
 @public
 class Project(Relation):
     parent: Relation
-    values: FrozenDict[str, NonSortKey[Unaliased[Value]]]
+    values: FrozenOrderedDict[str, NonSortKey[Unaliased[Value]]]
 
     def __init__(self, parent, values):
         _check_integrity(values.values(), {parent})
@@ -152,7 +152,7 @@ def schema(self):
 # TODO(kszucs): remove in favor of View
 @public
 class SelfReference(Reference):
-    values = FrozenDict()
+    values = FrozenOrderedDict()
 
 
 @public
@@ -187,7 +187,7 @@ class JoinLink(Node):
 class JoinChain(Relation):
     first: Reference
     rest: VarTuple[JoinLink]
-    values: FrozenDict[str, Unaliased[Value]]
+    values: FrozenOrderedDict[str, Unaliased[Value]]
 
     def __init__(self, first, rest, values):
         allowed_parents = {first}
@@ -259,8 +259,8 @@ class Limit(Simple):
 @public
 class Aggregate(Relation):
     parent: Relation
-    groups: FrozenDict[str, Unaliased[Column]]
-    metrics: FrozenDict[str, Unaliased[Scalar]]
+    groups: FrozenOrderedDict[str, Unaliased[Column]]
+    metrics: FrozenOrderedDict[str, Unaliased[Scalar]]
 
     def __init__(self, parent, groups, metrics):
         _check_integrity(groups.values(), {parent})
@@ -273,7 +273,7 @@ def __init__(self, parent, groups, metrics):
 
     @attribute
     def values(self):
-        return FrozenDict({**self.groups, **self.metrics})
+        return FrozenOrderedDict({**self.groups, **self.metrics})
 
     @attribute
     def schema(self):
@@ -285,7 +285,7 @@ class Set(Relation):
     left: Relation
     right: Relation
     distinct: bool = False
-    values = FrozenDict()
+    values = FrozenOrderedDict()
 
     def __init__(self, left, right, **kwargs):
         # convert to dictionary first, to get key-unordered comparison semantics
@@ -321,7 +321,7 @@ class Difference(Set):
 @public
 class PhysicalTable(Relation):
     name: str
-    values = FrozenDict()
+    values = FrozenOrderedDict()
 
 
 @public
@@ -356,7 +356,7 @@ class SQLQueryResult(Relation):
     query: str
     schema: Schema
     source: Any
-    values = FrozenDict()
+    values = FrozenOrderedDict()
 
 
 @public
@@ -378,12 +378,12 @@ class SQLStringView(Relation):
     child: Relation
     query: str
     schema: Schema
-    values = FrozenDict()
+    values = FrozenOrderedDict()
 
 
 @public
 class DummyTable(Relation):
-    values: FrozenDict[str, Value]
+    values: FrozenOrderedDict[str, Value]
 
     @attribute
     def schema(self):

ibis/expr/schema.py

@@ -5,7 +5,7 @@
 
 import ibis.expr.datatypes as dt
 from ibis.common.annotations import attribute
-from ibis.common.collections import FrozenDict, MapSet
+from ibis.common.collections import FrozenOrderedDict, MapSet
 from ibis.common.dispatch import lazy_singledispatch
 from ibis.common.exceptions import InputTypeError, IntegrityError
 from ibis.common.grounds import Concrete
@@ -19,7 +19,7 @@
 class Schema(Concrete, Coercible, MapSet):
     """An ordered mapping of str -> [datatype](./datatypes.qmd), used to hold a [Table](./expression-tables.qmd#ibis.expr.tables.Table)'s schema."""
 
-    fields: FrozenDict[str, dt.DataType]
+    fields: FrozenOrderedDict[str, dt.DataType]
     """A mapping of [](`str`) to
     [`DataType`](./datatypes.qmd#ibis.expr.datatypes.DataType)
     objects representing the type of each column."""

ibis/expr/tests/test_newrels.py

@@ -1711,3 +1711,12 @@ def test_mutate_ambiguty_check_not_too_strict():
         values={"id": first.id, "v": first.v, "v2": first.id},
     )
     assert second.op() == expected
+
+
+def test_projections_with_different_field_order_are_unequal():
+    t = ibis.table({"a": "int64", "b": "string"}, name="t")
+
+    t1 = t.select(a=1, b=2)
+    t2 = t.select(b=2, a=1)
+
+    assert not t1.equals(t2)

ibis/expr/tests/test_schema.py

@@ -203,6 +203,18 @@ def test_schema_mapping_api():
     assert tuple(s.items()) == tuple(zip(s.names, s.types))
 
 
+def test_schema_equality():
+    s1 = sch.schema({"a": "int64", "b": "string"})
+    s2 = sch.schema({"a": "int64", "b": "string"})
+    s3 = sch.schema({"b": "string", "a": "int64"})
+    s4 = sch.schema({"a": "int64", "b": "int64", "c": "string"})
+
+    assert s1 == s2
+    assert s1 != s3
+    assert s1 != s4
+    assert s3 != s2
+
+
 class BarSchema:
     a: int
     b: str