NULL values when there is no DEFAULT

- Post push fix for adding n_rows in row_log_t.

Returned accidentally removed undefinition of MYSQL_SERVER in net_serv.cc inside embedded server
(embedded server uses real_net_read/write only as a client)

Prevented attempt to clean up embedded server if it was not initialized

		NULL values when there is no DEFAULT

Copy and inplace algorithm works similarly for
NULL to NOT NULL conversion for the following cases:
(1) strict sql mode - Should give error.
(2) non-strict sql mode - Should give warnings alone
(3) alter ignore table command. - Should give warnings alone.

Changing columns WITH/WITHOUT SYSTEM VERSIONING doens't require to read data at
all. Thus it should be an instant operation.

Patch also fixes a bug when ALTER_COLUMN_UNVERSIONED wasn't passed to InnoDB
to change its internal structures.

change_field_versioning_try(): apply WITH/WITHOUT SYSTEM VERSIONING
change in SYS_COLUMNS for one field.

change_fields_versioning_try(): apply WITH/WITHOUT SYSTEM VERSIONING
change in SYS_COLUMNS for every changed field in a table.

change_fields_versioning_cache(): update cache for versioning property
of columns.

MDEV-16489 when lead() returns null on a datetime field, the result is treated as the literal string '[NULL]'

This bug happened for queries that used a materialized view that
renamed columns of the specifying query in an inner table of
an outer join. For such a query name resolution for a column
belonging the view could fail if the underlying column was
non-nullable.
When creating the defintion of the the temporary table for
the materialized view used in the inner part of an outer join
the definition of the non-nullable columns are created by the
function create_tmp_field_from_item() that names the columns
according to the names of the underlying columns. So these names
should be changed for the view column names.

This bug cannot be reproduced in 10.2 because there setup_fields()
called when preparing joins in the view specification effectively
renames the underlying columns in the function find_field_in_view().
In 10.3 this renaming was removed as improper
(see Monty's commit b478276b).

Add a Spider test to ensure that a bug similar to MDEV-11084 is not
re-introduced.  Spider would crash if the first partition was not used first.

Author:
  Eric Herman.

First Reviewer:
  Jacob Mathew.

Second Reviewer:
  Kentoku Shiba.

after 4461b0f9

cpk_scan should not be used if using it increases the cost of the query
plan.

MDEV-11071: Assertion `thd->transaction.stmt.is_empty()' failed in Locked_tables_list::unlock_locked_table

fix_length_and_dec now return result (error/OK)

When altering from DECIMAL to *INT UNIGNED or to BIT, go through val_decimal(),
to avoid truncation to the biggest possible signed integer
(0x7FFFFFFFFFFFFFFF / 9223372036854775807).

This problem was earlier fixed by the patch cb16d753
for MDEV-11337 Split Item::save_in_field() into virtual methods in Type_handler.

Adding tests only.

            materialized derived table/view that uses aliases is done

The problem appears when a column alias inside the materialized derived
table/view t1 definition coincides with the column name used in the
GROUP BY clause of t1. If the condition that can be pushed into t1
uses that ambiguous column name this column is determined as a column that
is used in the GROUP BY clause instead of the alias used in the projection
list of t1. That causes wrong result.
To prevent it resolve_ref_in_select_and_group() was changed.

Since MariaDB Server 10.2.2 (and MySQL 5.7), the default value of
innodb_checksum_algorithm is crc32 (CRC-32C), not the inefficient "innodb"
checksum. Change Mariabackup to use the same default, so that checksum
validation (when using the default algorithm on the server) will take less
time during mariabackup --backup. Also, mariabackup --prepare should be
a little faster, and the server should read backups faster, because the
page checksums would only be validated against CRC-32C.

fil_page_decompress(): Replaces fil_decompress_page().
Allow the caller detect errors. Remove
duplicated code. Use the "safe" instead of "fast" variants of
decompression routines.

fil_page_compress(): Replaces fil_compress_page().
The length of the input buffer always was srv_page_size (innodb_page_size).
Remove printouts, and remove the fil_space_t* parameter.

buf_tmp_buffer_t::reserved: Make private; the accessors acquire()
and release() will use atomic memory access.

buf_pool_reserve_tmp_slot(): Make static. Remove the second parameter.
Do not acquire any mutex. Remove the allocation of the buffers.

buf_tmp_reserve_crypt_buf(), buf_tmp_reserve_compression_buf():
Refactored away from buf_pool_reserve_tmp_slot().

buf_page_decrypt_after_read(): Make static, and simplify the logic.
Use the encryption buffer also for decompressing.

buf_page_io_complete(), buf_dblwr_process(): Check more failures.

fil_space_encrypt(): Simplify the debug checks.

fil_space_t::printed_compression_failure: Remove.

fil_get_compression_alg_name(): Remove.

fil_iterate(): Allocate a buffer for compression and decompression
only once, instead of allocating and freeing it for every page
that uses compression, during IMPORT TABLESPACE. Also, validate the
page checksum before decryption, and reduce the scope of some variables.

fil_page_is_index_page(), fil_page_is_lzo_compressed(): Remove (unused).

AbstractCallback::operator()(): Remove the parameter 'offset'.
The check for it in FetchIndexRootPages::operator() was basically
redundant and dead code since the previous refactoring.

Problem:
The problem was most likely introduced by a fix for MDEV-11597
(commit 5f0c31f9) which removed
the assignment "killed= KILL_BAD_DATA" from THD::raise_condition().

Before MDEV-11597, sp_head::execute() tested thd->killed after
looping through the SP instructions and exited with an error
if thd->killed is set. After MDEV-11597, sp_head::execute()
stopped to notice errors and set the OK status on top of the
error status, which crashed on assert.

Fix:
Making sp_cursor::fetch() return -1 if server_side_cursor->fetch(1)
left an error in the diagnostics area. This makes the statement
"err_status= i->execute(thd, &ip)" in sp_head::execute() set the
error code and correctly break the SP instruction loop and
return on error without setting the OK status.

Adjust the patch to match the variant accepted into the upstream:
undo the changes in ha_rocksdb::load_hidden_pk_value().

Added a testcase

This problem was earlier fixed by MDEV-14603.
Only adding 10.2 specific tests.

When type of the settable global variable innodb_change_buffering was
changed from string to ENUM in MDEV-12218, the "shadow" variable ibuf_use
stopped being updated as a result of SET GLOBAL innodb_change_buffering.
Only on InnoDB startup, the parameter innodb_change_buffering would
take effect.

ibuf_use: Remove, and use the global variable innodb_change_buffering.

When attempting to rename a table to a non-existing database,
InnoDB would misleadingly report "OS error 71" when in fact the
error code is InnoDB's own (OS_FILE_NOT_FOUND), and not report
both pathnames. Errors on rename could occur due to reasons
connected to either pathname.

os_file_handle_rename_error(): New function, to report errors in
renaming files.

Add variable rocksdb_remove_mariabackup_checkpoint.
If set, it will remove $rocksdb_datadir/mariabackup-checkpoint directory.
The variable is to be used by exclusively by mariabackup,
to remove temporary checkpoints.

log_copying_thread(): Keep copying redo log until the end has been
reached. (Previously, we would stop copying as soon as
the first batch of xtrabackup_copy_logfile() returned.)

log_copying: Remove. Use log_copying_running instead.

copy_logfile: Remove. Log copying will now only be invoked from
2 places: from xtrabackup_backup_func() for the initial batch,
and from log_copying_thread() until all of the log has been read.
Use the global variable metadata_to_lsn for determining if the
final part of the log is being copied.

xtrabackup_copy_log(): Add diagnostic messages for terminating
the copying. These messages should be dead code, because
log_group_read_log_seg() should be checking for the same.

xtrabackup_copy_logfile(): Correct the retrying logic.
If anything was successfully read, process the portion that
was read. On failure, let the caller close dst_log_file.

io_watching_thread(): Stop throttling during the last phase
of copying the log (metadata_to_lsn!=0). The final copying
of the log will now be performed in log_copying_thread().

stop_backup_threads(): Clean up the message about stopping
the log copying thread.

xtrabackup_backup_low(): Read metadata_to_lsn from the latest
checkpoint header page, even if it is the first page.
Let the log_copying_thread take care of copying all of
the redo log.