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, 7 insertions, 9 deletions

diff --git a/mysql-test/main/sp-dynamic.result b/mysql-test/main/sp-dynamic.result
index 9fa3bea1108..ad11763b523 100644
--- a/mysql-test/main/sp-dynamic.result
+++ b/mysql-test/main/sp-dynamic.result
@@ -64,9 +64,8 @@ execute stmt;
 deallocate prepare stmt;
 end|
 call p1()|
-ERROR HY000: This command is not supported in the prepared statement protocol yet
 call p1()|
-ERROR HY000: This command is not supported in the prepared statement protocol yet
+ERROR 42000: PROCEDURE p2 already exists
 drop procedure p1|
 create procedure p1()
 begin
@@ -75,9 +74,8 @@ execute stmt;
 deallocate prepare stmt;
 end|
 call p1()|
-ERROR HY000: This command is not supported in the prepared statement protocol yet
 call p1()|
-ERROR HY000: This command is not supported in the prepared statement protocol yet
+ERROR 42000: PROCEDURE test.p2 does not exist
 drop procedure p1|
 create procedure p1()
 begin
@@ -295,15 +293,15 @@ select * from t1|
 id	stmt_text	status
 1	select 1	supported
 2	flush tables	supported
-3	handler t1 open as ha	not supported
+3	handler t1 open as ha	supported
 4	analyze table t1	supported
-5	check table t1	not supported
+5	check table t1	supported
 6	checksum table t1	supported
-7	check table t1	not supported
+7	check table t1	supported
 8	optimize table t1	supported
 9	repair table t1	supported
 10	describe extended select * from t1	supported
-11	help help	not supported
+11	help help	supported
 12	show databases	supported
 13	show tables	supported
 14	show table status	supported
@@ -316,7 +314,7 @@ id	stmt_text	status
 21	call p1()	supported
 22	foo bar	syntax error
 23	create view v1 as select 1	supported
-24	alter view v1 as select 2	not supported
+24	alter view v1 as select 2	supported
 25	drop view v1	supported
 26	create table t2 (a int)	supported
 27	alter table t2 add (b int)	supported