- rework of correlation, continuing on #2668, #2746

- add support for correlations to propagate all the way in; because
correlations require context now, need to make sure a select enclosure
of any level takes effect any number of levels deep.
- fix what we said correlate_except() was supposed to do when we first
released #2668 - "the FROM clause is left intact if the correlated SELECT
is not used in the context of an enclosing SELECT..." - it was not
considering the "existing_froms" collection at all, and prohibited
additional FROMs from being placed in an any() or has().
- add test for multilevel any()
- lots of docs, including glossary entries as we really need to define
"WHERE clause", "columns clause" etc. so that we can explain correlation better
- based on the insight that a SELECT can correlate anything that ultimately
came from an enclosing SELECT that links to this one via WHERE/columns/HAVING/ORDER BY,
have the compiler keep track of the FROM lists that correspond in this way,
link it to the asfrom flag, so that we send to _get_display_froms() the exact
list of candidate FROMs to correlate.  no longer need any asfrom logic in the
Select() itself
- preserve 0.8.1's behavior for correlation when no correlate options are given, not
to mention 0.7 and prior's behavior of not propagating implicit correlation more than one level..
this is to reduce surprises/hard-to-debug situations when a user isn't trying
to correlate anything.

1 files changed, 99 insertions, 11 deletions

diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index 473a422a2..8b9f9cfa4 100644
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -2898,11 +2898,18 @@ class CorrelateTest(fixtures.TestBase, AssertsCompiledSQL):
                 "SELECT t1.a, t2.a FROM t1, t2 WHERE t2.a = "
                 "(SELECT t1.a WHERE t1.a = t2.a)")
 
-    def _assert_where_backwards_correlated(self, stmt):
-        self.assert_compile(
-                stmt,
-                "SELECT t2.a FROM t2 WHERE t2.a = "
-                "(SELECT t1.a FROM t2 WHERE t1.a = t2.a)")
+    # note there's no more "backwards" correlation after
+    # we've done #2746
+    #def _assert_where_backwards_correlated(self, stmt):
+    #    self.assert_compile(
+    #            stmt,
+    #            "SELECT t2.a FROM t2 WHERE t2.a = "
+    #            "(SELECT t1.a FROM t2 WHERE t1.a = t2.a)")
+
+    #def _assert_column_backwards_correlated(self, stmt):
+    #    self.assert_compile(stmt,
+    #            "SELECT t2.a, (SELECT t1.a FROM t2 WHERE t1.a = t2.a) "
+    #            "AS anon_1 FROM t2")
 
     def _assert_column_correlated(self, stmt):
         self.assert_compile(stmt,
@@ -2914,10 +2921,6 @@ class CorrelateTest(fixtures.TestBase, AssertsCompiledSQL):
                 "SELECT t1.a, t2.a, "
                 "(SELECT t1.a WHERE t1.a = t2.a) AS anon_1 FROM t1, t2")
 
-    def _assert_column_backwards_correlated(self, stmt):
-        self.assert_compile(stmt,
-                "SELECT t2.a, (SELECT t1.a FROM t2 WHERE t1.a = t2.a) "
-                "AS anon_1 FROM t2")
 
     def _assert_having_correlated(self, stmt):
         self.assert_compile(stmt,
@@ -2980,7 +2983,7 @@ class CorrelateTest(fixtures.TestBase, AssertsCompiledSQL):
 
     def test_correlate_except_exclusion_where(self):
         t1, t2, s1 = self._fixture()
-        self._assert_where_backwards_correlated(
+        self._assert_where_uncorrelated(
                 select([t2]).where(t2.c.a == s1.correlate_except(t2)))
 
     def test_correlate_except_inclusion_column(self):
@@ -2990,7 +2993,7 @@ class CorrelateTest(fixtures.TestBase, AssertsCompiledSQL):
 
     def test_correlate_except_exclusion_column(self):
         t1, t2, s1 = self._fixture()
-        self._assert_column_backwards_correlated(
+        self._assert_column_uncorrelated(
                 select([t2, s1.correlate_except(t2).as_scalar()]))
 
     def test_correlate_except_inclusion_from(self):
@@ -3003,6 +3006,11 @@ class CorrelateTest(fixtures.TestBase, AssertsCompiledSQL):
         self._assert_from_uncorrelated(
                 select([t2, s1.correlate_except(t2).alias()]))
 
+    def test_correlate_except_none(self):
+        t1, t2, s1 = self._fixture()
+        self._assert_where_all_correlated(
+                select([t1, t2]).where(t2.c.a == s1.correlate_except(None)))
+
     def test_correlate_except_having(self):
         t1, t2, s1 = self._fixture()
         self._assert_having_correlated(
@@ -3109,6 +3117,86 @@ class CorrelateTest(fixtures.TestBase, AssertsCompiledSQL):
         self.assert_compile(s1.correlate(t1, t2),
             "SELECT t1.a FROM t1, t2 WHERE t1.a = t2.a")
 
+    def test_correlate_except_froms(self):
+        # new as of #2748
+        t1 = table('t1', column('a'))
+        t2 = table('t2', column('a'), column('b'))
+        s = select([t2.c.b]).where(t1.c.a == t2.c.a)
+        s = s.correlate_except(t2).alias('s')
+
+        s2 = select([func.foo(s.c.b)]).as_scalar()
+        s3 = select([t1], order_by=s2)
+
+        self.assert_compile(s3,
+            "SELECT t1.a FROM t1 ORDER BY "
+            "(SELECT foo(s.b) AS foo_1 FROM "
+            "(SELECT t2.b AS b FROM t2 WHERE t1.a = t2.a) AS s)"
+        )
+
+    def test_multilevel_froms_correlation(self):
+        # new as of #2748
+        p = table('parent', column('id'))
+        c = table('child', column('id'), column('parent_id'), column('pos'))
+
+        s = c.select().where(c.c.parent_id == p.c.id).order_by(c.c.pos).limit(1)
+        s = s.correlate(p)
+        s = exists().select_from(s).where(s.c.id == 1)
+        s = select([p]).where(s)
+        self.assert_compile(s,
+            "SELECT parent.id FROM parent WHERE EXISTS (SELECT * "
+            "FROM (SELECT child.id AS id, child.parent_id AS parent_id, "
+            "child.pos AS pos FROM child WHERE child.parent_id = parent.id "
+            "ORDER BY child.pos LIMIT :param_1) WHERE id = :id_1)")
+
+    def test_no_contextless_correlate_except(self):
+        # new as of #2748
+
+        t1 = table('t1', column('x'))
+        t2 = table('t2', column('y'))
+        t3 = table('t3', column('z'))
+
+        s = select([t1]).where(t1.c.x == t2.c.y).\
+            where(t2.c.y == t3.c.z).correlate_except(t1)
+        self.assert_compile(s,
+            "SELECT t1.x FROM t1, t2, t3 WHERE t1.x = t2.y AND t2.y = t3.z")
+
+    def test_multilevel_implicit_correlation_disabled(self):
+        # test that implicit correlation with multilevel WHERE correlation
+        # behaves like 0.8.1, 0.7 (i.e. doesn't happen)
+        t1 = table('t1', column('x'))
+        t2 = table('t2', column('y'))
+        t3 = table('t3', column('z'))
+
+        s = select([t1.c.x]).where(t1.c.x == t2.c.y)
+        s2 = select([t3.c.z]).where(t3.c.z == s.as_scalar())
+        s3 = select([t1]).where(t1.c.x == s2.as_scalar())
+
+        self.assert_compile(s3,
+            "SELECT t1.x FROM t1 "
+            "WHERE t1.x = (SELECT t3.z "
+            "FROM t3 "
+            "WHERE t3.z = (SELECT t1.x "
+            "FROM t1, t2 "
+            "WHERE t1.x = t2.y))"
+        )
+
+    def test_from_implicit_correlation_disabled(self):
+        # test that implicit correlation with immediate and
+        # multilevel FROM clauses behaves like 0.8.1 (i.e. doesn't happen)
+        t1 = table('t1', column('x'))
+        t2 = table('t2', column('y'))
+        t3 = table('t3', column('z'))
+
+        s = select([t1.c.x]).where(t1.c.x == t2.c.y)
+        s2 = select([t2, s])
+        s3 = select([t1, s2])
+
+        self.assert_compile(s3,
+            "SELECT t1.x, y, x FROM t1, "
+            "(SELECT t2.y AS y, x FROM t2, "
+            "(SELECT t1.x AS x FROM t1, t2 WHERE t1.x = t2.y))"
+        )
+
 class CoercionTest(fixtures.TestBase, AssertsCompiledSQL):
     __dialect__ = 'default'