Allow for multiple FOLLOWING/PRECEDING in a window range

Altered the range specification for window functions to allow
for two of the same PRECEDING or FOLLOWING keywords in a range
by allowing for the left side of the range to be positive
and for the right to be negative, e.g. (1, 3) is
"1 FOLLOWING AND 3 FOLLOWING".

Change-Id: I7d3a6c641151bb49219104968d18dac2266f3db8
Fixes: #4053

1 files changed, 18 insertions, 12 deletions

diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index 05893d748..053619f46 100644
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -2426,31 +2426,37 @@ class SelectTest(fixtures.TestBase, AssertsCompiledSQL):
             "(ORDER BY mytable.myid RANGE BETWEEN "
             ":param_1 PRECEDING AND :param_2 FOLLOWING)"
             " AS anon_1 FROM mytable",
-            {'param_1': 5, 'param_2': 10}
+            checkparams={'param_1': 5, 'param_2': 10}
         )
 
-    def test_over_invalid_framespecs(self):
-        assert_raises_message(
-            exc.ArgumentError,
-            "Preceding value must be a negative integer, zero, or None",
-            func.row_number().over, range_=(5, 10)
+        self.assert_compile(
+            select([func.row_number().over(order_by=expr, range_=(1, 10))]),
+            "SELECT row_number() OVER "
+            "(ORDER BY mytable.myid RANGE BETWEEN "
+            ":param_1 FOLLOWING AND :param_2 FOLLOWING)"
+            " AS anon_1 FROM mytable",
+            checkparams={'param_1': 1, 'param_2': 10}
         )
 
-        assert_raises_message(
-            exc.ArgumentError,
-            "Following value must be a positive integer, zero, or None",
-            func.row_number().over, range_=(-5, -8)
+        self.assert_compile(
+            select([func.row_number().over(order_by=expr, range_=(-10, -1))]),
+            "SELECT row_number() OVER "
+            "(ORDER BY mytable.myid RANGE BETWEEN "
+            ":param_1 PRECEDING AND :param_2 PRECEDING)"
+            " AS anon_1 FROM mytable",
+            checkparams={'param_1': 10, 'param_2': 1}
         )
 
+    def test_over_invalid_framespecs(self):
         assert_raises_message(
             exc.ArgumentError,
-            "Integer or None expected for preceding value",
+            "Integer or None expected for range value",
             func.row_number().over, range_=("foo", 8)
         )
 
         assert_raises_message(
             exc.ArgumentError,
-            "Integer or None expected for following value",
+            "Integer or None expected for range value",
             func.row_number().over, range_=(-5, "foo")
         )