bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT

        Collections were treated mistakenly, so the counter for the final UNION operation
        received the wrong value.
        As a fix we implement Item_func_buffer::Transporter::start_collection() method,
        where we set the proper operation and the operand counter.
        start_poly() and start_line() were also modified to function correctly for the 
        polygon as a part of a collection.

per-file comments:
  mysql-test/r/gis-precise.result
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        test result updated.

  mysql-test/t/gis-precise.test
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        test case added.

  sql/item_geofunc.cc
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        start_collection() implemented.

  sql/item_geofunc.h
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        Item_func_buffer::Transporter::start_collection() defined.

mysql-test/r/gis-precise.result

@@ -212,3 +212,6 @@ GEOMETRYCOLLECTION(POLYGON((0 0,1 9,8 2,0 0),(2 2,2 7,3 2,2 2)),LINESTRING(0 0,5
 SELECT astext(ST_BUFFER(LineStringFromText('LINESTRING(0 0,1 1)'),0));
 astext(ST_BUFFER(LineStringFromText('LINESTRING(0 0,1 1)'),0))
 LINESTRING(0 0,1 1)
+SELECT Round(ST_Area(ST_BUFFER(MultipointFromText('MULTIPOINT(7 7,3 7,7 2,7 4 ,7 7)'), 3)), 5);
+Round(ST_Area(ST_BUFFER(MultipointFromText('MULTIPOINT(7 7,3 7,7 2,7 4 ,7 7)'), 3)), 5)
+78.68426

mysql-test/t/gis-precise.test

@@ -114,3 +114,6 @@ SELECT astext(ST_UNION (
 
 #bug 801189 ST_BUFFER asserts if radius = 0
 SELECT astext(ST_BUFFER(LineStringFromText('LINESTRING(0 0,1 1)'),0));
+
+#buf 801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
+SELECT Round(ST_Area(ST_BUFFER(MultipointFromText('MULTIPOINT(7 7,3 7,7 2,7 4 ,7 7)'), 3)), 5);

sql/item_geofunc.cc

@@ -1284,6 +1284,18 @@ int Item_func_buffer::Transporter::add_point_buffer(double x, double y)
 
 int Item_func_buffer::Transporter::start_line()
 {
+  if (buffer_op == Gcalc_function::op_difference)
+  {
+    skip_line= TRUE;
+    return 0;
+  }
+  
+  m_nshapes= 0;
+
+  if (m_fn->reserve_op_buffer(2))
+    return 1;
+  last_shape_pos= m_fn->get_next_operation_pos();
+  m_fn->add_operation(buffer_op, 0);
   m_npoints= 0;
   int_start_line();
   return 0;
@@ -1292,11 +1304,25 @@ int Item_func_buffer::Transporter::start_line()
 
 int Item_func_buffer::Transporter::start_poly()
 {
-  ++m_nshapes;
+  m_nshapes= 1;
+
+  if (m_fn->reserve_op_buffer(2))
+    return 1;
+  last_shape_pos= m_fn->get_next_operation_pos();
+  m_fn->add_operation(buffer_op, 0);
   return Gcalc_operation_transporter::start_poly();
 }
 
 
+int Item_func_buffer::Transporter::complete_poly()
+{
+  if (Gcalc_operation_transporter::complete_poly())
+    return 1;
+  m_fn->add_operands_to_op(last_shape_pos, m_nshapes);
+  return 0;
+}
+
+
 int Item_func_buffer::Transporter::start_ring()
 {
   m_npoints= 0;
@@ -1304,8 +1330,20 @@ int Item_func_buffer::Transporter::start_ring()
 }
 
 
+int Item_func_buffer::Transporter::start_collection(int n_objects)
+{
+  if (m_fn->reserve_op_buffer(1))
+    return 1;
+  m_fn->add_operation(Gcalc_function::op_union, n_objects);
+  return 0;
+}
+
+
 int Item_func_buffer::Transporter::add_point(double x, double y)
 {
+  if (skip_line)
+    return 0;
+
   if (m_npoints && x == x2 && y == y2)
     return 0;
 
@@ -1374,9 +1412,14 @@ int Item_func_buffer::Transporter::complete()
 
 int Item_func_buffer::Transporter::complete_line()
 {
+  if (!skip_line)
+  {
     if (complete())
       return 1;
     int_complete_line();
+    m_fn->add_operands_to_op(last_shape_pos, m_nshapes);
+  }
+  skip_line= FALSE;
   return 0;
 }
 
@@ -1396,7 +1439,6 @@ String *Item_func_buffer::val_str(String *str_value)
   double dist= args[1]->val_real();
   Geometry_buffer buffer;
   Geometry *g;
-  uint32 union_pos;
   uint32 srid= 0;
   String *str_result= NULL;
   Transporter trn(&func, &collector, dist);
@@ -1418,17 +1460,9 @@ String *Item_func_buffer::val_str(String *str_value)
     goto mem_error;
   }
 
-  if (func.reserve_op_buffer(2))
-    goto mem_error;
-  /* will specify operands later */
-  union_pos= func.get_next_operation_pos();
-  func.add_operation((dist > 0.0) ? Gcalc_function::op_union :
-                                    Gcalc_function::op_difference, 0);
-
   if (g->store_shapes(&trn))
     goto mem_error;
 
-  func.add_operands_to_op(union_pos, trn.m_nshapes);
   collector.prepare_operation();
   if (func.alloc_states())
     goto mem_error;

sql/item_geofunc.h

@@ -26,6 +26,7 @@
 #endif
 
 #include "gcalc_slicescan.h"
+#include "gcalc_tools.h"
 
 class Item_geometry_func: public Item_str_func
 {
@@ -298,18 +299,28 @@ protected:
     int add_last_edge_buffer();
     int add_point_buffer(double x, double y);
     int complete();
-  public:
     int m_nshapes;
+    Gcalc_function::op_type buffer_op;
+    int last_shape_pos;
+    bool skip_line;
+
+  public:
     Transporter(Gcalc_function *fn, Gcalc_heap *heap, double d) :
-      Gcalc_operation_transporter(fn, heap), m_npoints(0), m_d(d), m_nshapes(0)
+      Gcalc_operation_transporter(fn, heap), m_npoints(0), m_d(d),
+      m_nshapes(0), buffer_op((d > 0.0) ? Gcalc_function::op_union :
+                                          Gcalc_function::op_difference),
+      skip_line(FALSE)
     {}
     int single_point(double x, double y);
     int start_line();
     int complete_line();
     int start_poly();
+    int complete_poly();
     int start_ring();
     int complete_ring();
     int add_point(double x, double y);
+
+    int start_collection(int n_objects);
   };
   Gcalc_heap collector;
   Gcalc_function func;