source/projects/datalog/test/python/test_datalog_evaluator.py

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"""Query evaluation unit tests."""
from datalog.easy import read, select
from datalog.types import (
CachedDataset,
Constant,
Dataset,
LVar,
PartlyIndexedDataset,
Rule,
TableIndexedDataset,
)
import pytest
DBCLS = [Dataset, CachedDataset, TableIndexedDataset, PartlyIndexedDataset]
@pytest.mark.parametrize("db_cls,", DBCLS)
def test_id_query(db_cls):
"""Querying for a constant in the dataset."""
ab = (
Constant("a"),
Constant("b"),
)
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assert not select(
db_cls([], []),
(
"a",
"b",
),
)
assert select(db_cls([ab], []), ("a", "b",)) == [
(
(("a", "b"),),
{},
)
]
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@pytest.mark.parametrize("db_cls,", DBCLS)
def test_lvar_query(db_cls):
"""Querying for a binding in the dataset."""
d = read("""a(b). a(c).""", db_cls=db_cls)
assert select(d, ("a", "X")) == [
((("a", "b"),), {"X": "b"}),
((("a", "c"),), {"X": "c"}),
]
@pytest.mark.parametrize("db_cls,", DBCLS)
def test_lvar_unification(db_cls):
"""Querying for MATCHING bindings in the dataset."""
d = read("""edge(b, c). edge(c, c).""", db_cls=db_cls)
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assert (
select(
d,
(
"edge",
"X",
"X",
),
)
== [((("edge", "c", "c"),), {"X": "c"})]
)
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@pytest.mark.parametrize("db_cls,", DBCLS)
def test_rule_join(db_cls):
"""Test a basic join query - the parent -> grandparent relation."""
child = Constant("child")
gc = Constant("grandchild")
d = read(
"""
child(a, b).
child(b, c).
child(b, d).
child(b, e).
grandchild(A, B) :-
child(A, C),
child(C, B).
""",
db_cls=db_cls,
)
assert select(d, ("grandchild", "a", "X",)) == [
((("grandchild", "a", "c"),), {"X": "c"}),
((("grandchild", "a", "d"),), {"X": "d"}),
((("grandchild", "a", "e"),), {"X": "e"}),
]
@pytest.mark.parametrize("db_cls,", DBCLS)
def test_antijoin(db_cls):
"""Test a query containing an antijoin."""
d = read(
"""
a(foo, bar).
b(foo, bar).
a(baz, qux).
% matching b(baz, qux). is our antijoin test
no-b(X, Y) :-
a(X, Y),
~b(X, Z).
""",
db_cls=db_cls,
)
assert select(d, ("no-b", "X", "Y")) == [
((("no-b", "baz", "qux"),), {"X": "baz", "Y": "qux"})
]
@pytest.mark.parametrize("db_cls,", DBCLS)
def test_nested_antijoin(db_cls):
"""Test a query which negates a subquery which uses an antijoin.
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Shouldn't exercise anything more than `test_antjoin` does, but it's an interesting case since you
actually can't capture the same semantics using a single query. Antijoins can't propagate positive
information (create lvar bindings) so I'm not sure you can express this another way without a
different evaluation strategy.
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"""
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d = read(
"""
a(foo, bar).
b(foo, bar).
a(baz, qux).
b(baz, quack).
b-not-quack(X, Y) :-
b(X, Y),
~=(Y, quack).
a-no-nonquack(X, Y) :-
a(X, Y),
~b-not-quack(X, Y).
""",
db_cls=db_cls,
)
assert select(d, ("a-no-nonquack", "X", "Y")) == [
((("a-no-nonquack", "baz", "qux"),), {"X": "baz", "Y": "qux"})
]
@pytest.mark.parametrize("db_cls,", DBCLS)
def test_alternate_rule(db_cls):
"""Testing that both recursion and alternation work."""
d = read(
"""
edge(a, b).
edge(b, c).
edge(c, d).
edge(d, e).
edge(e, f).
path(A, B) :-
edge(A, B).
path(A, B) :-
edge(A, C),
path(C, B).
""",
db_cls=db_cls,
)
# Should be able to recurse to this one.
assert select(d, ("path", "a", "f")) == [((("path", "a", "f"),), {})]
# FIXME (arrdem 2019-06-13):
#
# This test is BROKEN for the simple dataset. In order for left-recursive production rules to
# work, they have to ground out somewhere. Under the naive, cache-less datalog this is an
# infinite left recursion. Under the cached versions, the right-recursion becomes iteration over
# an incrementally realized list which ... is weird but does work because the recursion grounds
# out in iterating over an empty list on the 2nd round then falls through to the other production
# rule which generates ground tuples and feeds everything.
#
# It's not clear how to make this work with the current (lack of) query planner on the naive db as
# really fixing this requires some amount of insight into the data dependency structure and may
# involve reordering rules.
@pytest.mark.parametrize("db_cls,", DBCLS)
def test_alternate_rule_lrec(db_cls):
"""Testing that both recursion and alternation work."""
d = read(
"""
edge(a, b).
edge(b, c).
edge(c, d).
edge(d, e).
edge(e, f).
path(A, B) :-
edge(A, B).
path(A, B) :-
path(A, C),
edge(C, B).
""",
db_cls=db_cls,
)
# Should be able to recurse to this one.
assert select(d, ("path", "a", "f")) == [((("path", "a", "f"),), {})]
@pytest.mark.parametrize("db_cls,", DBCLS)
def test_cojoin(db_cls):
"""Tests that unification occurs correctly."""
d = read(
"""
edge(a, b).
edge(b, c).
edge(c, d).
edge(d, e).
edge(e, f).
edge(c, q).
two_path(A, B, C) :- edge(A, B), edge(B, C).
""",
db_cls=db_cls,
)
# Should be able to recurse to this one.
assert [t for t, _ in select(d, ("two_path", "A", "B", "C"))] == [
(("two_path", "a", "b", "c"),),
(("two_path", "b", "c", "d"),),
(("two_path", "b", "c", "q"),),
(("two_path", "c", "d", "e"),),
(("two_path", "d", "e", "f"),),
]