From 14b976991b348e401c781d7931b8e6201e1b0eac Mon Sep 17 00:00:00 2001
From: mariadb-AndreyPiskunov <andrey.piskunov@mariadb.com>
Date: Fri, 2 Sep 2022 14:14:33 +0300
Subject: [PATCH] Remade dropValue

---
 utils/regr/regr_sxy.cpp | 21 ++++++++++++++-------
 utils/regr/regr_sxy.h   |  2 +-
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/utils/regr/regr_sxy.cpp b/utils/regr/regr_sxy.cpp
index 5354306ac..6b7cf2c2e 100644
--- a/utils/regr/regr_sxy.cpp
+++ b/utils/regr/regr_sxy.cpp
@@ -147,20 +147,27 @@ mcsv1_UDAF::ReturnCode regr_sxy::evaluate(mcsv1Context* context, static_any::any
   }
   return mcsv1_UDAF::SUCCESS;
 }
-/*
+
 mcsv1_UDAF::ReturnCode regr_sxy::dropValue(mcsv1Context* context, ColumnDatum* valsDropped)
 {
   double valy = toDouble(valsDropped[0]);
   double valx = toDouble(valsDropped[1]);
   struct regr_sxy_data* data = (struct regr_sxy_data*)context->getUserData()->data;
 
-  data->avgy -= valy;
-
-  data->avgx -= valx;
-
-  data->cxy -= valx * valy;
+  long double avgyPrev = data->avgy;
+  long double avgxPrev = data->avgx;
+  long double cxyPrev = data->cxy;
   --data->cnt;
+  uint64_t cnt = data->cnt;
+  long double dx = valx - avgxPrev;
+
+  avgyPrev -= (valy - avgyPrev) / cnt;
+  avgxPrev -= dx / cnt;
+  cxyPrev -= dx * (valy - avgyPrev);
+
+  data->avgx = avgxPrev;
+  data->avgy = avgyPrev;
+  data->cxy = cxyPrev;
 
   return mcsv1_UDAF::SUCCESS;
 }
-*/
\ No newline at end of file
diff --git a/utils/regr/regr_sxy.h b/utils/regr/regr_sxy.h
index 6bcbf6500..bdfffc14a 100644
--- a/utils/regr/regr_sxy.h
+++ b/utils/regr/regr_sxy.h
@@ -70,7 +70,7 @@ class regr_sxy : public mcsv1_UDAF
 
   virtual ReturnCode evaluate(mcsv1Context* context, static_any::any& valOut);
 
-  // virtual ReturnCode dropValue(mcsv1Context* context, ColumnDatum* valsDropped);
+  virtual ReturnCode dropValue(mcsv1Context* context, ColumnDatum* valsDropped);
 
  protected:
 };