With the MDEV-15562 instant DROP COLUMN, clustered index records
will contain traces of dropped columns, as follows:

In ROW_FORMAT=REDUNDANT, dropped columns will be stored as 0 bytes,
but they will consume 1 or 2 bytes per column in the record header.

In ROW_FORMAT=COMPACT or ROW_FORMAT=DYNAMIC, dropped columns will
be stored as NULL if allowed. This will consume 1 bit per nullable
column.

In ROW_FORMAT=COMPACT or ROW_FORMAT=DYNAMIC, dropped NOT NULL columns
will be stored as 0 bytes if allowed. This will consume 1 byte per
NOT NULL variable-length column. Fixed-length columns will be stored
using the fixed number of bytes.

The metadata record will be 20 bytes larger than user records, because
it will contain a metadata BLOB pointer.

We must refuse ALGORITHM=INSTANT (and require a table rebuild) if
the metadata record would grow too big to fit in the index page.

If SQL_MODE includes STRICT_TRANS_TABLES or STRICT_ALL_TABLES, we should
refuse ALGORITHM=INSTANT if the maximum length of user records would
exceed the maximum size of an index page, similar to what
row_create_index_for_mysql() does during CREATE TABLE. This limit
would kick in when the default values for any instantly added columns
in the metadata record are NULL or short, but the allowed maximum values
are long.

instant_alter_column_possible(): Add the parameter "bool strict" to
enable checks for the user record size, and always check the metadata
record size.

test case:
t1 is a spider engine table;
  CREATE TABLE `t1` (
  `id` int(11) NOT NULL DEFAULT '0',
  `name` char(64) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=SPIDER

query: "select * from t1 where name  not like 'x%' " would dispatch "select xxx name name like 'x%' " to remote mysqld, is wrong

MDEV-17362: SIGSEGV in JOIN::optimize_inner or Assertion `fixed == 0' failed in  Item_equal::fix_fields, server crashes after 2nd execution of PS

Move reinitialisation of pushdown variables for every query, because it used now not only for derived tables.

Turning initializing code into constructors.

srv_start(): Restore the call to buf_pool_invalidate() that
was removed in commit 09af00cb.
It turns out that the call is necessary to work around a bug
that should be fixed in MDEV-19229.

* Fix valgrind error caused by vp/spider.handler test.

* Fix valgrind error caused by vp/spider.ha test.

add changes of test results

MDEV-16530 Spider datanodes needs adjusted wait_timeout for long running queries on spider head node (#1258)

Add the following parameters.

- spider_remote_wait_timeout
  Set remote wait_timeout at connecting for improvement performance of
  connection if you know.
  -1,0      : No set.
  1 or more : Seconds.
  The default value is -1

- spider_wait_timeout
  The wait time to remote servers.
  -1,0      : No set.
  1 or more : Seconds.
  The default value is 604800

remove a sometimes misleading word INPLACE from error message

MDEV-18993 The keep-alive connection (set spider_conn_recycle_mode = 1) in spider would cause cash in MariaDB (#1269)

Fix the following valgrind error.

==94390== Thread 29:
==94390== Invalid read of size 8
==94390== at 0x78389D: thd_increment_bytes_sent (sql_class.cc:4265)
==94390== by 0xC8EC46: net_real_write (net_serv.cc:730)
==94390== by 0xC8E0C8: net_flush (net_serv.cc:383)
==94390== by 0xC8E4D0: net_write_command (net_serv.cc:521)
==94390== by 0xADCE61: cli_advanced_command (client.c:468)
==94390== by 0xAE3CAF: mysql_close_slow_part (client.c:3671)
==94390== by 0xAE3D28: mysql_close (client.c:3683)
==94390== by 0x149E69A8: spider_db_mbase::disconnect() (spd_db_mysql.cc:2217)
==94390== by 0x1491EA26: spider_db_disconnect(st_spider_conn*) (spd_db_conn.cc:297)
==94390== by 0x14948EBE: spider_free_conn_alloc(st_spider_conn*) (spd_conn.cc:196)
==94390== by 0x1494B26A: spider_free_conn(st_spider_conn*) (spd_conn.cc:1251)
==94390== by 0x1494941F: spider_free_conn_from_trx(st_spider_transaction*, st_spider_conn*, bool, bool, int*) (spd_conn.cc:315)
==94390== Address 0x1f0e0990 is 4,832 bytes inside a block of size 25,728 free'd
==94390== at 0x4C2ACBD: free (vg_replace_malloc.c:530)
==94390== by 0x13F5545: my_free (my_malloc.c:222)
==94390== by 0x6C75B7: ilink::operator delete(void*, unsigned long) (sql_list.h:618)
==94390== by 0x77B9F6: THD::~THD() (sql_class.cc:1724)
==94390== by 0x1494FCE0: spider_bg_conn_action(void*) (spd_conn.cc:2580)
==94390== by 0x4E3DDD4: start_thread (in /usr/lib64/libpthread-2.17.so)
==94390== by 0x5FBFEAC: clone (in /usr/lib64/libc-2.17.so)
==94390== Block was alloc'd at
==94390== at 0x4C29BC3: malloc (vg_replace_malloc.c:299)
==94390== by 0x13F4DFA: my_malloc (my_malloc.c:101)
==94390== by 0x1491CF06: ilink::operator new(unsigned long) (sql_list.h:614)
==94390== by 0x1494F7FD: spider_bg_conn_action(void*) (spd_conn.cc:2501)
==94390== by 0x4E3DDD4: start_thread (in /usr/lib64/libpthread-2.17.so)
==94390== by 0x5FBFEAC: clone (in /usr/lib64/libc-2.17.so)
==94390== Invalid write of size 8
==94390== at 0x7838AF: thd_increment_bytes_sent (sql_class.cc:4265)
==94390== by 0xC8EC46: net_real_write (net_serv.cc:730)
==94390== by 0xC8E0C8: net_flush (net_serv.cc:383)
==94390== by 0xC8E4D0: net_write_command (net_serv.cc:521)
==94390== by 0xADCE61: cli_advanced_command (client.c:468)
==94390== by 0xAE3CAF: mysql_close_slow_part (client.c:3671)
==94390== by 0xAE3D28: mysql_close (client.c:3683)
==94390== by 0x149E69A8: spider_db_mbase::disconnect() (spd_db_mysql.cc:2217)
==94390== by 0x1491EA26: spider_db_disconnect(st_spider_conn*) (spd_db_conn.cc:297)
==94390== by 0x14948EBE: spider_free_conn_alloc(st_spider_conn*) (spd_conn.cc:196)
==94390== by 0x1494B26A: spider_free_conn(st_spider_conn*) (spd_conn.cc:1251)
==94390== by 0x1494941F: spider_free_conn_from_trx(st_spider_transaction*, st_spider_conn*, bool, bool, int*) (spd_conn.cc:315)
==94390== Address 0x1f0e0990 is 4,832 bytes inside a block of size 25,728 free'd
==94390== at 0x4C2ACBD: free (vg_replace_malloc.c:530)
==94390== by 0x13F5545: my_free (my_malloc.c:222)
==94390== by 0x6C75B7: ilink::operator delete(void*, unsigned long) (sql_list.h:618)
==94390== by 0x77B9F6: THD::~THD() (sql_class.cc:1724)
==94390== by 0x1494FCE0: spider_bg_conn_action(void*) (spd_conn.cc:2580)
==94390== by 0x4E3DDD4: start_thread (in /usr/lib64/libpthread-2.17.so)
==94390== by 0x5FBFEAC: clone (in /usr/lib64/libc-2.17.so)
==94390== Block was alloc'd at
==94390== at 0x4C29BC3: malloc (vg_replace_malloc.c:299)
==94390== by 0x13F4DFA: my_malloc (my_malloc.c:101)
==94390== by 0x1491CF06: ilink::operator new(unsigned long) (sql_list.h:614)
==94390== by 0x1494F7FD: spider_bg_conn_action(void*) (spd_conn.cc:2501)
==94390== by 0x4E3DDD4: start_thread (in /usr/lib64/libpthread-2.17.so)
==94390== by 0x5FBFEAC: clone (in /usr/lib64/libc-2.17.so)

and don't pass BUILD_CONFIG twice, once is enough.

When freeing a file page, write a MLOG_INIT_FREE_PAGE record.
This allows us to avoid page flush and instead punch holes later,
in the page flushing. To implement that, we may want to make
buf_page_t::file_page_was_freed available in non-debug builds.

Crash recovery can choose to ignore or apply the record.

In BtrBulk::finish() we must not write this record, because
redo logging is being disabled for the page.

fseg_free_page_func(): Avoid an unnecessary tablespace ID lookup.
The callers should pass the tablespace that they already know.

The regression that was reported in MDEV-19212 occurred due to use
of macros that did not ensure that the arguments have compatible
types.

ut_2pow_remainder(), ut_2pow_round(), ut_calc_align(): Define as
inline function templates.

UT_CALC_ALIGN(): Define as a macro, because this is used in
compile_time_assert(). Only starting with C++11 (MariaDB 10.4)
we could define the inline functions as constexpr.

os_mem_alloc_large(): Invoke the macro ut_2pow_round() with the
correct argument type.

innobase_large_page_size, innobase_use_large_pages,
os_use_large_pages, os_large_page_size: Remove.
Simply refer to opt_large_page_size, my_use_large_pages.

xtrabackup_backup_func(): If the log checkpoint header changed
since we last read it, search for the most recent checkpoint again.
Otherwise, we could corrupt the backup of the redo log, because the
least significant bits of checkpoint_lsn_start would not match
log_sys->log.lsn.

btr_page_free(): Renamed from btr_page_free_low().
If scrubbing is enabled, zero out the page with proper redo logging.
Only pass ahi=true to fseg_free_page() if the page is actually indexed.

fil_space_t::modify_check(): Renamed from fsp_space_modify_check().

fsp_init_file_page(): Define inline.

because FindBoost.cmake won't do it

On Linux, <fcntl.h> declares open(2) as having a nonnull first argument.
In GCC 8, if a function with nonnull argument is called, that argument
will be silently assumed to nonnull along the same code path. Hence,
later nullness checks for this argument can be optimized away.

Similar to MDEV-15587, the fix is to ensure that functions with
nonnull arguments are not being called with NULL.

This bug caused a crash in mysqlbinlog, which was invoking
create_temp_file() with the argument dir=NULL. The affected test was
binlog.binlog_mysqlbinlog_base64. It would display the following message
before crashing:

mysqlbinlog: O_TMPFILE is not supported on (null) (disabling future attempts)
Segmentation fault

thanks @FaramosCZ

Even if Makefile for some reason was checked in in a submodule,
it is still a generated file, will be cleaned, won't be in a source
package. One cannot jump to conclusions if it doesn't exist.

This is a follow-up to MDEV-18733. As part of that fix, we made
dict_check_sys_tables() skip tables that would be dropped by
row_mysql_drop_garbage_tables().

DICT_ERR_IGNORE_DROP: A new mode where the file should not be attempted
to be opened.

dict_load_tablespace(): Do not try to load the tablespace if
DICT_ERR_IGNORE_DROP has been specified.

row_mysql_drop_garbage_tables(): Pass the DICT_ERR_IGNORE_DROP mode.

fil_space_for_table_exists_in_mem(): Remove a parameter.
The only caller that passed print_error_if_does_not_exist=true
was row_drop_single_table_tablespace().