MDEV-6575: main.view --ps-protocol fails in ANALYZE code

- After PREPARE is done, save the value of thd->select_number
  (this is what will be assigned to next select_lex object)
- Restore the value at each execution of the prepared statement.

sql/sql_prepare.cc

@@ -160,6 +160,20 @@ public:
   uint param_count;
   uint last_errno;
   uint flags;
+  /*
+    The value of thd->select_number at the end of the PREPARE phase.
+
+    The issue is: each statement execution opens VIEWs, which may cause 
+    select_lex objects to be created, and select_number values to be assigned.
+
+    On the other hand, PREPARE assigns select_number values for triggers and
+    subqueries.
+
+    In order for select_number values from EXECUTE not to conflict with
+    select_number values from PREPARE, we keep the number and set it at each
+    execution.
+  */
+  uint select_number_after_prepare;
   char last_error[MYSQL_ERRMSG_SIZE];
 #ifndef EMBEDDED_LIBRARY
   bool (*set_params)(Prepared_statement *st, uchar *data, uchar *data_end,
@@ -3455,6 +3469,8 @@ bool Prepared_statement::prepare(const char *packet, uint packet_len)
     trans_rollback_implicit(thd);
     thd->mdl_context.release_transactional_locks();
   }
+  
+  select_number_after_prepare= thd->select_number;
 
   lex_end(lex);
   cleanup_stmt();
@@ -3581,7 +3597,8 @@ Prepared_statement::execute_loop(String *expanded_query,
   Reprepare_observer reprepare_observer;
   bool error;
   int reprepare_attempt= 0;
-
+  
+  thd->select_number= select_number_after_prepare;
   /* Check if we got an error when sending long data */
   if (state == Query_arena::STMT_ERROR)
   {