Use correct frame bounds when window frame was not specified

Also added win_bit.result (result values checked)

mysql-test/r/win_bit.result

+create table t1 (
+pk int primary key,
+a int,
+b int
+);
+create table t2 (
+pk int primary key,
+a int,
+b int
+);
+insert into t1 values
+( 1 , 0, 1),
+( 2 , 0, 2),
+( 3 , 1, 4),
+( 4 , 1, 8),
+( 5 , 2, 32),
+( 6 , 2, 64),
+( 7 , 2, 128),
+( 8 , 2, 16);
+insert into t2 values
+( 1 , 0, 2),
+( 2 , 0, 2),
+( 3 , 1, 4),
+( 4 , 1, 4),
+( 5 , 2, 16),
+( 6 , 2, 64),
+( 7 , 2, 128),
+( 8 , 2, 16);
+# Test bit functions on only one partition.
+select pk, a, b,
+bit_or(b) over (order by pk) as bit_or,
+bit_and(b) over (order by pk) as bit_and,
+bit_xor(b) over (order by pk) as bit_xor
+from t1;
+pk	a	b	bit_or	bit_and	bit_xor
+1	0	1	1	1	1
+2	0	2	3	0	3
+3	1	4	7	0	7
+4	1	8	15	0	15
+5	2	32	47	0	47
+6	2	64	111	0	111
+7	2	128	239	0	239
+8	2	16	255	0	255
+select pk, a, b,
+bit_or(b) over (order by pk) as bit_or,
+bit_and(b) over (order by pk) as bit_and,
+bit_xor(b) over (order by pk) as bit_xor
+from t2;
+pk	a	b	bit_or	bit_and	bit_xor
+1	0	2	2	2	2
+2	0	2	2	2	0
+3	1	4	6	0	4
+4	1	4	6	0	0
+5	2	16	22	0	16
+6	2	64	86	0	80
+7	2	128	214	0	208
+8	2	16	214	0	192
+# Test multiple partitions with bit functions.
+select pk, a, b,
+bit_or(b) over (partition by a order by pk) as bit_or,
+bit_and(b) over (partition by a order by pk) as bit_and,
+bit_xor(b) over (partition by a order by pk) as bit_xor
+from t1;
+pk	a	b	bit_or	bit_and	bit_xor
+1	0	1	1	1	1
+2	0	2	3	0	3
+3	1	4	4	4	4
+4	1	8	12	0	12
+5	2	32	32	32	32
+6	2	64	96	0	96
+7	2	128	224	0	224
+8	2	16	240	0	240
+select pk, a, b,
+bit_or(b) over (partition by a order by pk) as bit_or,
+bit_and(b) over (partition by a order by pk) as bit_and,
+bit_xor(b) over (partition by a order by pk) as bit_xor
+from t2;
+pk	a	b	bit_or	bit_and	bit_xor
+1	0	2	2	2	2
+2	0	2	2	2	0
+3	1	4	4	4	4
+4	1	4	4	4	0
+5	2	16	16	16	16
+6	2	64	80	0	80
+7	2	128	208	0	208
+8	2	16	208	0	192
+# Test remove function for bit functions using a sliding window.
+select pk, a, b,
+bit_or(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) as bit_or,
+bit_and(b) over (partition by a order by pk) as bit_and,
+bit_xor(b) over (partition by a order by pk) as bit_xor
+from t1;
+pk	a	b	bit_or	bit_and	bit_xor
+1	0	1	3	1	1
+2	0	2	3	0	3
+3	1	4	12	4	4
+4	1	8	12	0	12
+5	2	32	96	32	32
+6	2	64	224	0	96
+7	2	128	208	0	224
+8	2	16	144	0	240
+select pk, a, b,
+bit_or(b) over (partition by a order by pk) as bit_or,
+bit_and(b) over (partition by a order by pk) as bit_and,
+bit_xor(b) over (partition by a order by pk) as bit_xor
+from t2;
+pk	a	b	bit_or	bit_and	bit_xor
+1	0	2	2	2	2
+2	0	2	2	2	0
+3	1	4	4	4	4
+4	1	4	4	4	0
+5	2	16	16	16	16
+6	2	64	80	0	80
+7	2	128	208	0	208
+8	2	16	208	0	192
+drop table t1;
+drop table t2;
+

sql/sql_window.cc

@@ -820,16 +820,30 @@ class Frame_n_rows_following : public Frame_cursor
 
 Frame_cursor *get_frame_cursor(Window_frame *frame, bool is_top_bound)
 {
-  // TODO-cvicentiu When a frame is not specified, which is the frame type
-  // that we will use?
-  // Postgres uses RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW.
-  // For now we use UNBOUNDED FOLLOWING and UNBOUNDED PRECEDING.
   if (!frame)
   {
+    /*
+      The docs say this about the lack of frame clause:
+
+        Let WD be a window structure descriptor.
+        ...
+        If WD has no window framing clause, then
+        Case:
+        i) If the window ordering clause of WD is not present, then WF is the
+           window partition of R.
+        ii) Otherwise, WF consists of all rows of the partition of R that
+           precede R or are peers of R in the window ordering of the window
+           partition defined by the window ordering clause.
+
+        For case #ii, the frame bounds essentially are "RANGE BETWEEN UNBOUNDED
+        PRECEDING AND CURRENT ROW".
+        For the case #i, without ordering clause all rows are considered peers,
+        so again the same frame bounds can be used.
+    */
     if (is_top_bound)
       return new Frame_unbounded_preceding;
     else
-      return new Frame_unbounded_following;
+      return new Frame_range_current_row_bottom;
   }
 
   Window_frame_bound *bound= is_top_bound? frame->top_bound :