does not return error

Corrected the code of st_select_lex::find_table_def_in_with_clauses() for
a proper identification of CTE references used in embedded CTEs.

When storing '0001-01-01 10:20:30x', execution went throw the last code
branch in Field_time::store_TIME_with_warning(), around the test
for (ltime->year || ltime->month). This then resulted into wrong results
because:

1. Field_time::store_TIME() does not check YYYYMM against zero.
  It assumes that ltime->days and ltime->hours are already properly set.
  So it mixed days to hours, even when YYYYMM was not zero.

2. Field_time_hires::store_TIME() does not check YYYYMM against zero.
  It assumes that ltime->year, ltime->month, ltime->days and ltime->hours
  are already properly set. So it always mixed days and even months(!) and years(!)
  to hours, using pack_time(). This gave even worse results comparing to #2.

3. Field_timef::store_TIME() did not check the entire YYYYMM for being zero.
  It only checked MM, but did not check YYYY. In case of a zero MM,
  it mixed days to hours, even if YYYY was not zero.
  The wrong code was in TIME_to_longlong_time_packed().

In the new reduction Field_time::store_TIME_with_warning() is responsible
to prepare the YYYYYMMDD part properly in all code branches
(with trailing garbage like 'x' and without trailing garbage).
It was reorganized into a more straightforward style.

Field_time:store_TIME(), Field_time_hires::store_TIME() and
TIME_to_longlong_time_packed() were fixed to do a DBUG_ASSERT
on non-zero ltime->year or ltime->month. The code testing ltime->month
was removed from TIME_to_longlong_time_packed(), as it's now
properly done on the caller level.

Truncation was moved from Field_timef::store_TIME() to
Field_time::store_TIME_with_warning().

So now all thee methods Field_time*::store_TIME() assume a properly
set input value:
- Only zero ltime->year and ltime->month are allowed.
- The value must be already properly truncated according to decimals()
  (this will help to add rounding soon, see MDEV-8894)

A "const" qualifier was added to the argument of Field_time*::store_TIME().

Virtial_tmp_table did not set the "field_index" member for its Fields.
Fixing Virtual_tmp_table::add() to set "field_index" to the Field's ordinal position
inside the table, like a normal TABLE does, for consistency.

Although, this flaw did not seem to cause any bugs, having field_index properly
set is helpful for debugging purposes.

1st. Create_field does not have function vers_sys_field() kind of handy
function, second I think Create_field and Field should not divert much , and
Field does have this function.

2nd. Versioning column does not have NOT_NULL_FLAG, since they can never be
null. So I have added NOT_NULL_FLAG.

3rd. Since I added NOT_NULL_FLAG this created one issue , versioning column
of datatype bigint unsigned were getting NO_DEFAULT_VALUE_FLAG. This makes
test like versioning.insert to fail, Reason being If a column gets this
flag if we insert 'default' value it will generate error(that is why ) test
was failing. So now versioning column wont get NO_DEFAULT_VALUE_FLAG flag.

Problem:-
  create or replace table t1 (pk int auto_increment primary key invisible, i int);
  alter table t1 modify pk int invisible;
 This last alter makes a invisible column which is not null and does not
 have default value.

Analysis:-
 This is caused because our error check for NOT_NULL_FLAG and
 NO_DEFAULT_VALUE_FLAG flag misses this sql_field , but this is not the fault
 of error check :).Actually this field come via mysql_prepare_alter_table
 and it does not have NO_DEFAULT_VALUE_FLAG flag turned on. (If it was create
 table NO_DEFAULT_VALUE_FLAG would have turned on Column_definition::check)
 and this would have generated error.

Solution:-
 I have moved the error check to kind last of mysql_prepare_create_table
 because upto this point we have applied NO_DEFAULT_VALUE_FLAG to required
 column.

Problem:- If we create table field with dynamic default value then that
 field always gets NULL value.

Analyze:- This is because in fill_record we simple continue at Invisible
 column because we though that share->default_values(default value is
 always copied into table->record[0] before insert) will have a default
 value for them(which is true for constant defaults , but not for dynamic
 defaults).

Solution:- We simple set all_fields_have_value to null , and this will
make call to update_default_fields (in the case of dynamic default), And
default expr will be evaluted and value will be set in field.

This will make it easier to how memory allocation is done when debugging
with either DBUG or gdb.

Will especially help when debugging stored procedures

Main change is a name argument as second argument to init_alloc_root()
init_sql_alloc()

Other things:
- Added DBUG_ENTER/EXIT to some Virtual_tmp_table functions

This is to make it a proper class function.

When identifying a table name the following should be taken into account:
a CTE name cannot be qualified with a database name, otherwise the table
name is considered as the name of a non-CTE table.

With trx_sys_t::rw_trx_ids removal, MVCC snapshot overhead became
slightly higher. That is instead of copying an array we now have to
iterate LF_HASH. All this done under trx_sys.mutex protection.

This patch moves MVCC snapshot out of trx_sys.mutex.

Clean-ups:

Removed MVCC: doesn't make too much sense to keep it in a separate class
anymore.

Refactored ReadView so that it now calls register()/deregister() routines
(it was vice versa before).

ReadView doesn't have friends anymore. :(

Even less trx_sys.mutex references.

- Changing sp_rcontext::m_var_items from list of Item to list of Item_field
- Renaming sp_rcontext::get_item() to get_variable() and changing
  its return type from Item* to Item_field *
- Adding sp_rcontext::get_parameter() and sp_rcontext::set_parameter(),
  wrappers for get_variable() and set_variable() with extra DBUG_ASSERT.
  Using new methods instead of get_variable()/set_variable() in
  relevant places.

serialisation_list was supposed to instantly give minimum registered
transaction serialisation number. However maintaining and accessing
this list requires global mutex protection.

Since we already take MVCC snapshot by iterating trx_sys_t::rw_trx_hash,
it is cheap to integrate minimum registered transaction lookup into this
iteration.

Setting non_null value drops null_value flag.
Part 2 of 3.
Part 1 was 10.2 fix.
Part 3 is test for Connector C.

Take snapshot of registered read-write transaction identifiers directly
from rw_trx_hash. It immediately saves one trx_sys.mutex lock, reduces
size of another critical section protected by this mutex, and makes
further optimisations like removing trx_sys_t::serialisation_list
possible.

Downside of this approach is bigger overhead for view opening, because
iterating LF_HASH is more expensive compared to taking snapshot of an
array. However for low concurrency overhead difference is negligible,
while for high concurrency mutex is much bigger evil.

Currently we still take trx_sys.mutex to serialise ReadView creation.
This is required to keep serialisation_list ordered by trx->no as well
as not to let purge thread to create more recent snapshot while another
thread gets suspended during creation of older snapshot. This will
become completely mutex free along with serialisation_list removal.

Compared to previous implementation removing element from rw_trx_hash
and serialisation_list is not atomic. We disregard all possible bad
consequences (if there're any) since it will be solved along with
serialisation_list removal.

trx->state change must be guarded by trx->mutex.
Moved mutex locking to MVCC::view_close().

trx_undo_mem_create_at_db_start(): Do not read TRX_UNDO_TRX_NO
unless the field is known to be valid, that is, the transaction
has been serialized and trx_purge_add_undo_to_history() has been
invoked.

Normally InnoDB pages would be zero-initialized on allocation
(since MySQL 5.5 or so), but the undo log pages skip that
mechanism. So, reused undo log pages can contain garbage.
Undo log headers can start at any offset (there can be
multiple undo log headers in the same undo log page).
Therefore, because the TRX_UNDO_TRX_NO is never explicitly
initialized on undo log header creation, its contents may
be garbage.

extra/mariabackup/xtrabackup.cc: In function ‘ulint xb_process_datadir(const char*, const char*, handle_datadir_entry_func_t)’:
extra/mariabackup/xtrabackup.cc:4534:1: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
 xb_process_datadir(
 ^~~~~~~~~~~~~~~~~~
mariabackup/xtrabackup.cc:4607:11: note: ‘snprintf’ output 2 or more bytes (assuming 4001) into a destination of size 4000
   snprintf(dbpath, sizeof(dbpath), "%s/%s", path, dbinfo.name);
   ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

gcc7 warning:

sql/table.cc: In member function ‘int TABLE_SHARE::init_from_binary_frm_image(THD*, bool, const uchar*, size_t)’:
sql/table.cc:2032:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
           if (vers_can_native)
           ^~
sql/table.cc:2037:9: note: here
         default:
         ^~~~~~~

trx_write_serialisation_history(): Only invoke trx_sysf_get()
to exclusively lock the TRX_SYS page if some change really
has to be written to the page.

On transaction commit, we will still write some binlog and
Galera WSREP XID information.

FIXME: If this information has to be written, it should be
partitioned into the rollback segment pages.

InnoDB maintains an internal persistent sequence of transaction
identifiers. This sequence is used for assigning both transaction
start identifiers (DB_TRX_ID=trx->id) and end identifiers (trx->no)
as well as end identifiers for the mysql.transaction_registry table
that was introduced in MDEV-12894.

TRX_SYS_TRX_ID_WRITE_MARGIN: Remove. After this many updates of
the sequence we used to update the TRX_SYS page. We can avoid accessing
the TRX_SYS page if we modify the InnoDB startup so that resurrecting
the sequence from other pages of the transaction system.

TRX_SYS_TRX_ID_STORE: Deprecate. The field only exists for the purpose
of upgrading from an earlier version of MySQL or MariaDB.

Starting with this fix, MariaDB will rely on the fields
TRX_UNDO_TRX_ID, TRX_UNDO_TRX_NO in the undo log header page of
each non-committed transaction, and on the new field
TRX_RSEG_MAX_TRX_ID in rollback segment header pages.

Because of this change, setting innodb_force_recovery=5 or 6 may cause
the system to recover with trx_sys.get_max_trx_id()==0. We must adjust
checks for invalid DB_TRX_ID and PAGE_MAX_TRX_ID accordingly.

We will change the startup and shutdown messages to display the
trx_sys.get_max_trx_id() in addition to the log sequence number.

trx_sys_t::flush_max_trx_id(): Remove.

trx_undo_mem_create_at_db_start(), trx_undo_lists_init():
Add an output parameter max_trx_id, to be updated from
TRX_UNDO_TRX_ID, TRX_UNDO_TRX_NO.

TRX_RSEG_MAX_TRX_ID: New field, for persisting
trx_sys.get_max_trx_id() at the time of the latest transaction commit.
Startup is not reading the undo log pages of committed transactions.
We want to avoid additional page accesses on startup, as well as
trouble when all undo logs have been emptied.
On startup, we will simply determine the maximum value from all pages
that are being read anyway.

TRX_RSEG_FORMAT: Redefined from TRX_RSEG_MAX_SIZE.

Old versions of InnoDB wrote uninitialized garbage to unused data fields.
Because of this, we cannot simply introduce a new field in the
rollback segment pages and expect it to be always zero, like it would
if the database was created by a recent enough InnoDB version.

Luckily, it looks like the field TRX_RSEG_MAX_SIZE was always written
as 0xfffffffe. We will indicate a new subformat of the page by writing
0 to this field. This has the nice side effect that after a downgrade
to older versions of InnoDB, transactions should fail to allocate any
undo log, that is, writes will be blocked. So, there is no problem of
getting corrupted transaction identifiers after downgrading.

trx_rseg_t::max_size: Remove.

trx_rseg_header_create(): Remove the parameter max_size=ULINT_MAX.

trx_purge_add_undo_to_history(): Update TRX_RSEG_MAX_SIZE
(and TRX_RSEG_FORMAT if needed). This is invoked on transaction commit.

trx_rseg_mem_restore(): If TRX_RSEG_FORMAT contains 0,
read TRX_RSEG_MAX_SIZE.

trx_rseg_array_init(): Invoke trx_sys.init_max_trx_id(max_trx_id + 1)
where max_trx_id was the maximum that was encountered in the rollback
segment pages and the undo log pages of recovered active, XA PREPARE,
or some committed transactions. (See trx_purge_add_undo_to_history()
which invokes trx_rsegf_set_nth_undo(..., FIL_NULL, ...);
not all committed transactions will be immediately detached from the
rollback segment header.)

trx_rseg_mem_restore(): Update the max_trx_id from the undo log pages.

trx_sys_init_at_db_start(): Remove; merge with trx_lists_init_at_db_start().

trx_undo_lists_init(): Move to the only calling module, trx0rseg.cc.

trx_undo_mem_create_at_db_start(): Declare globally. Return the number
of pages.

trx_rseg_mem_create(): Initialize rseg->curr_size and rseg->max_size.

trx_rseg_create(), trx_temp_rseg_create():
Do not call trx_rseg_mem_restore().

trx_undo_page_get_prev_rec(), trx_undo_page_get_last_rec(),
trx_undo_page_get_first_rec(), trx_undo_page_get_start():
Move to the only caller, trx0undo.cc.

Add some const qualifiers.

trx_rseg_get_nth_undo(), trx_rsegf_undo_find_free():
Add a const qualifier, and remove the unused parameter mtr_t*.

trx_sysf_t: Remove.

trx_sysf_get(): Return the TRX_SYS page, not a pointer within it.

trx_sysf_rseg_get_space(), trx_sysf_rseg_get_page_no():
Remove a parameter, and merge the declaration and definition.
Take the TRX_SYS page as a parameter.

TRX_SYS_N_RSEGS: Correct the comment.

trx_sysf_rseg_find_free(), trx_sys_update_mysql_binlog_offset(),
trx_sys_update_wsrep_checkpoint(): Take the TRX_SYS page as a parameter.

trx_rseg_header_create(): Add a parameter for the TRX_SYS page.

trx_sysf_rseg_set_space(), trx_sysf_rseg_set_page_no(): Remove;
merge to the only caller, trx_rseg_header_create().

srv_init_abort_low(): Call srv_shutdown_bg_undo_sources() so that if
startup aborts while creating InnoDB system tables, the shutdown will
proceed correctly.

server crash in JOIN::fix_all_splittings_in_plan

Cost formulas must take into account the case when a splittable table
has now rows.

null_value was not properly reset when setting parameter value

Only give warning if warnings > 2, as there is no plan to change
the current behavior.

- When adding LEX_CSTRING to String, we are now checking that
  string is \0 terminated (as normally LEX_CSTRING should be
  usable for printf(). In the cases when one wants to avoid the
  checking one can use String->append(ptr, length) instead of just
  String->append(LEX_CSTRING*)

This preserves const str for constant strings

Other things
- A few variables where changed from LEX_STRING to LEX_CSTRING
- Incident_log_event::Incident_log_event and record_incident where
  changed to take LEX_CSTRING* as an argument instead of LEX_STRING

This is to make it easier to use the
create_mysqld_error_find_printf_error tool to find wrong print

Rename was done as the old 'name' hide the original item name.