MDEV-35437 Suppress "This function has the same name" warnings in I_S queries

Sending "This function has the same name" during I_S quries was too verbose.
Suppressing these warnings.

Now warnings are sent only during CREATE FUNCTION and during function call.

mysql-test/main/sp.result

@@ -9101,3 +9101,27 @@ ERROR 42000: You have an error in your SQL syntax; check the manual that corresp
 #
 # End of 10.7 tests
 #
+#
+# Start of 11.8 tests
+#
+#
+# MDEV-35437 Suppress "This function has the same name" warnings in I_S queries
+#
+CREATE FUNCTION upper() RETURNS TEXT RETURN 'upper';
+Warnings:
+Note	1585	This function 'upper' has the same name as a native function
+SELECT test.upper();
+test.upper()
+upper
+Warnings:
+Note	1585	This function 'upper' has the same name as a native function
+SELECT ROUTINE_NAME FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_SCHEMA='test' AND ROUTINE_NAME='upper';
+ROUTINE_NAME
+upper
+SELECT SPECIFIC_NAME FROM INFORMATION_SCHEMA.PARAMETERS WHERE SPECIFIC_SCHEMA='test' AND SPECIFIC_NAME='upper';
+SPECIFIC_NAME
+upper
+DROP FUNCTION upper;
+#
+# End of 11.8 tests
+#

mysql-test/main/sp.test

@@ -10699,3 +10699,24 @@ CREATE PROCEDURE sp() SELECT @;
 --echo #
 --echo # End of 10.7 tests
 --echo #
+
+
+--echo #
+--echo # Start of 11.8 tests
+--echo #
+
+--echo #
+--echo # MDEV-35437 Suppress "This function has the same name" warnings in I_S queries
+--echo #
+
+CREATE FUNCTION upper() RETURNS TEXT RETURN 'upper';
+SELECT test.upper();
+# I_S queries should not produce warnings
+SELECT ROUTINE_NAME FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_SCHEMA='test' AND ROUTINE_NAME='upper';
+SELECT SPECIFIC_NAME FROM INFORMATION_SCHEMA.PARAMETERS WHERE SPECIFIC_SCHEMA='test' AND SPECIFIC_NAME='upper';
+DROP FUNCTION upper;
+
+
+--echo #
+--echo # End of 11.8 tests
+--echo #

sql/sql_show.cc

@@ -7174,6 +7174,27 @@ int store_schema_proc(THD *thd, TABLE *table, TABLE *proc_table,
 }
 
 
+/*
+  Suppress "This function 'func' has the same name as a native function"
+  during INFORMATION_SCHEMA.ROUTINES queries.
+*/
+class Native_fct_name_collision_error_handler : public Internal_error_handler
+{
+public:
+  bool handle_condition(THD *thd,
+                        uint sql_errno,
+                        const char* sqlstate,
+                        Sql_condition::enum_warning_level *level,
+                        const char* msg,
+                        Sql_condition ** cond_hdl) override
+  {
+    if (sql_errno == ER_NATIVE_FCT_NAME_COLLISION)
+      return true;
+    return false;
+  }
+};
+
+
 int fill_schema_proc(THD *thd, TABLE_LIST *tables, COND *cond)
 {
   TABLE *proc_table;
@@ -7184,6 +7205,7 @@ int fill_schema_proc(THD *thd, TABLE_LIST *tables, COND *cond)
   char definer[USER_HOST_BUFF_SIZE];
   enum enum_schema_tables schema_table_idx=
     get_schema_table_idx(tables->schema_table);
+  Native_fct_name_collision_error_handler err_handler;
   DBUG_ENTER("fill_schema_proc");
 
   strxmov(definer, thd->security_ctx->priv_user, "@",
@@ -7254,6 +7276,7 @@ int fill_schema_proc(THD *thd, TABLE_LIST *tables, COND *cond)
 
   if (res)
     goto err;
+  thd->push_internal_handler(&err_handler);
 
   res= schema_table_idx == SCH_PROCEDURES ?
     store_schema_proc(thd, table, proc_table, &lookup, full_access,definer) :
@@ -7264,6 +7287,7 @@ int fill_schema_proc(THD *thd, TABLE_LIST *tables, COND *cond)
       store_schema_proc(thd, table, proc_table, &lookup, full_access, definer) :
       store_schema_params(thd, table, proc_table, &lookup, full_access, definer);
   }
+  thd->pop_internal_handler();
 
 err:
   if (proc_table->file->inited)