MDEV-16708: Unsupported commands for prepared statements

Withing this task the following changes were made:
- Added sending of metadata info in prepare phase for the admin related
  command (check table, checksum table, repair, optimize, analyze).

- Refactored implmentation of HELP command to support its execution in
  PS mode

- Added support for execution of LOAD INTO and XA- related statements
  in PS mode

- Modified mysqltest.cc to run statements in PS mode unconditionally
  in case the option --ps-protocol is set. Formerly, only those statements
  were executed using PS protocol that matched the hard-coded regular expression

- Fixed the following issues:
    The statement
      explain select (select 2)
    executed in regular and PS mode produces different results:

    MariaDB [test]> prepare stmt from "explain select (select 2)";
    Query OK, 0 rows affected (0,000 sec)
    Statement prepared
    MariaDB [test]> execute stmt;
    +------+-------------+-------+------+---------------+------+---------+------+------+----------------+
    | id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra          |
    +------+-------------+-------+------+---------------+------+---------+------+------+----------------+
    |    1 | PRIMARY     | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | No tables used |
    |    2 | SUBQUERY    | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | No tables used |
    +------+-------------+-------+------+---------------+------+---------+------+------+----------------+
    2 rows in set (0,000 sec)
    MariaDB [test]> explain select (select 2);
    +------+-------------+-------+------+---------------+------+---------+------+------+----------------+
    | id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra          |
    +------+-------------+-------+------+---------------+------+---------+------+------+----------------+
    |    1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | No tables used |
    +------+-------------+-------+------+---------------+------+---------+------+------+----------------+
    1 row in set, 1 warning (0,000 sec)

    In case the statement
      CREATE TABLE t1 SELECT * FROM (SELECT 1 AS a, (SELECT a+0)) a
    is run in PS mode it fails with the error
      ERROR 1054 (42S22): Unknown column 'a' in 'field list'.

- Uniform handling of read-only variables both in case the SET var=val
  statement is executed as regular or prepared statememt.

- Fixed assertion firing on handling LOAD DATA statement for temporary tables

- Relaxed assert condition in the function lex_end_stage1() by adding
  the commands SQLCOM_ALTER_EVENT, SQLCOM_CREATE_PACKAGE,
  SQLCOM_CREATE_PACKAGE_BODY to a list of supported command

- Removed raising of the error ER_UNSUPPORTED_PS in the function
  check_prepared_statement() for the ALTER VIEW command

- Added initialization of the data memember st_select_lex_unit::last_procedure
  (assign NULL value) in the constructor

  Without this change the test case main.ctype_utf8 fails with the following
  report in case it is run with the optoin --ps-protocol.
    mysqltest: At line 2278: query 'VALUES (_latin1 0xDF) UNION VALUES(_utf8'a' COLLATE utf8_bin)' failed: 2013: Lost connection

- The following bug reports were fixed:
      MDEV-24460: Multiple rows result set returned from stored
                  routine over prepared statement binary protocol is
                  handled incorrectly
      CONC-519: mariadb client library doesn't handle server_status and
                warnign_count fields received in the packet
                COM_STMT_EXECUTE_RESPONSE.

  Reasons for these bug reports have the same nature and caused by
  missing loop iteration on results sent by server in response to
  COM_STMT_EXECUTE packet.

  Enclosing of statements for processing of COM_STMT_EXECUTE response
  in the construct like
    do
    {
      ...
    } while (!mysql_stmt_next_result());
  fixes the above mentioned bug reports.

1 files changed, 34 insertions, 16 deletions

diff --git a/sql/sql_admin.cc b/sql/sql_admin.cc
index aa66291929c..1c32e9d57cc 100644
--- a/sql/sql_admin.cc
+++ b/sql/sql_admin.cc
@@ -489,6 +489,38 @@ static bool wsrep_toi_replication(THD *thd, TABLE_LIST *tables)
 }
 #endif /* WITH_WSREP */
 
+
+/**
+  Collect field names of result set that will be sent to a client
+
+  @param      thd     Thread data object
+  @param[out] fields  List of fields whose metadata should be collected for
+                      sending to client
+*/
+
+void fill_check_table_metadata_fields(THD *thd, List<Item>* fields)
+{
+  Item *item;
+
+  item= new (thd->mem_root) Item_empty_string(thd, "Table", NAME_CHAR_LEN * 2);
+  item->set_maybe_null();
+  fields->push_back(item, thd->mem_root);
+
+  item= new (thd->mem_root) Item_empty_string(thd, "Op", 10);
+  item->set_maybe_null();
+  fields->push_back(item, thd->mem_root);
+
+  item= new (thd->mem_root) Item_empty_string(thd, "Msg_type", 10);
+  item->set_maybe_null();
+  fields->push_back(item, thd->mem_root);
+
+  item= new (thd->mem_root) Item_empty_string(thd, "Msg_text",
+                                              SQL_ADMIN_MSG_TEXT_SIZE);
+  item->set_maybe_null();
+  fields->push_back(item, thd->mem_root);
+}
+
+
 /*
   RETURN VALUES
     FALSE Message sent to net (admin operation went ok)
@@ -512,7 +544,6 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
 {
   TABLE_LIST *table;
   List<Item> field_list;
-  Item *item;
   Protocol *protocol= thd->protocol;
   LEX *lex= thd->lex;
   int result_code;
@@ -524,21 +555,8 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
   DBUG_ENTER("mysql_admin_table");
   DBUG_PRINT("enter", ("extra_open_options: %u", extra_open_options));
 
-  field_list.push_back(item= new (thd->mem_root)
-                       Item_empty_string(thd, "Table",
-                                         NAME_CHAR_LEN * 2), thd->mem_root);
-  item->set_maybe_null();
-  field_list.push_back(item= new (thd->mem_root)
-                       Item_empty_string(thd, "Op", 10), thd->mem_root);
-  item->set_maybe_null();
-  field_list.push_back(item= new (thd->mem_root)
-                       Item_empty_string(thd, "Msg_type", 10), thd->mem_root);
-  item->set_maybe_null();
-  field_list.push_back(item= new (thd->mem_root)
-                       Item_empty_string(thd, "Msg_text",
-                                         SQL_ADMIN_MSG_TEXT_SIZE),
-                       thd->mem_root);
-  item->set_maybe_null();
+  fill_check_table_metadata_fields(thd, &field_list);
+
   if (protocol->send_result_set_metadata(&field_list,
                             Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
     DBUG_RETURN(TRUE);