Fix for bug#42009: SELECT into variable gives different results to direct SELECT

Problem: storing "SELECT ... INTO @var ..." results in variables we used val_xxx()
methods which returned results of the current row. 
So, in some cases (e.g. SELECT DISTINCT, GROUP BY or HAVING) we got data
from the first row of a new group (where we evaluate a clause) instead of
data from the last row of the previous group.

Fix: use val_xxx_result() counterparts to get proper results.


mysql-test/r/distinct.result:
  Fix for bug#42009: SELECT into variable gives different results to direct SELECT
    - results adjusted.
mysql-test/r/user_var.result:
  Fix for bug#42009: SELECT into variable gives different results to direct SELECT
    - test result.
mysql-test/t/user_var.test:
  Fix for bug#42009: SELECT into variable gives different results to direct SELECT
    - test case.
sql/item_func.cc:
  Fix for bug#42009: SELECT into variable gives different results to direct SELECT
    - Item_func_set_user_var::save_item_result() added to evaluate and store 
      an item's result into a user variable.
sql/item_func.h:
  Fix for bug#42009: SELECT into variable gives different results to direct SELECT
    - Item_func_set_user_var::save_item_result() added to evaluate and store 
      an item's result into a user variable.
sql/sql_class.cc:
  Fix for bug#42009: SELECT into variable gives different results to direct SELECT
    - use Item_func_set_user_var::save_item_result() to store results into user 
      variables.

1 files changed, 35 insertions, 0 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index 55324923fe2..519b476ccf8 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -4147,6 +4147,41 @@ Item_func_set_user_var::check(bool use_result_field)
 }
 
 
+/**
+  @brief Evaluate and store item's result.
+  This function is invoked on "SELECT ... INTO @var ...".
+  
+  @param    item    An item to get value from.
+*/
+
+void Item_func_set_user_var::save_item_result(Item *item)
+{
+  DBUG_ENTER("Item_func_set_user_var::save_item_result");
+
+  switch (cached_result_type) {
+  case REAL_RESULT:
+    save_result.vreal= item->val_result();
+    break;
+  case INT_RESULT:
+    save_result.vint= item->val_int_result();
+    unsigned_flag= item->unsigned_flag;
+    break;
+  case STRING_RESULT:
+    save_result.vstr= item->str_result(&value);
+    break;
+  case DECIMAL_RESULT:
+    save_result.vdec= item->val_decimal_result(&decimal_buff);
+    break;
+  case ROW_RESULT:
+  default:
+    // Should never happen
+    DBUG_ASSERT(0);
+    break;
+  }
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   This functions is invoked on SET @variable or @variable:= expression.