MDEV-15073: Generic UDAF parser code in server for windows functionsbb-10.4-MDEV-15073

Added support for usual agreggate UDF (UDAF)
Added remove() call support for more efficient window function processing
Added example of aggregate UDF with efficient windows function support

1 files changed, 15 insertions, 0 deletions

diff --git a/sql/sql_udf.h b/sql/sql_udf.h
index 6e6fed2a81a..d1f2ae7bfb0 100644
--- a/sql/sql_udf.h
+++ b/sql/sql_udf.h
@@ -47,6 +47,7 @@ typedef struct st_udf_func
   Udf_func_deinit func_deinit;
   Udf_func_clear func_clear;
   Udf_func_add func_add;
+  Udf_func_add func_remove;
   ulong usage_count;
 } udf_func;
 
@@ -131,6 +132,20 @@ class udf_handler :public Sql_alloc
     func(&initid, &f_args, &is_null, &error);
     *null_value= (my_bool) (is_null || error);
   }
+  bool supports_removal()
+  { return MY_TEST(u_d->func_remove); }
+  void remove(my_bool *null_value)
+  {
+    DBUG_ASSERT(u_d->func_remove);
+    if (get_arguments())
+    {
+      *null_value=1;
+      return;
+    }
+    Udf_func_add func= u_d->func_remove;
+    func(&initid, &f_args, &is_null, &error);
+    *null_value= (my_bool) (is_null || error);
+  }
   String *val_str(String *str,String *save_str);
 };