This is mostly to document that read_to_buffer can read more than 65K.
Also changed merge_buffers to return bool instead of int

As thd->alloc() and new automatically calls my_error(ER_OUTOFMEORY)
there is no reason to call mem_alloc_error()

Other things:
- Fixed bug in mysql_unpack_partition() where lex.part_info was
  changed even if it would be a null pointer

Performance schema likely/unlikely assume that performance schema
is enabled by default, which causes a performance degradation for
default installations that doesn't have performance schema enabled.

Fixed by changing the likely/unlikely in PS to assume it's
not enabled. This can be changed by compiling with
-DPSI_ON_BY_DEFAULT

Other changes:
- Added psi_likely/psi_unlikely that is depending on
  PSI_ON_BY_DEFAULT. psi_likely() is assumed to be true
  if PS is enabled.
- Added likely/unlikely to some PS interface code.
- Moved pfs_enabled to mysys (was initialized but not used before)
- Added "if (pfs_likely(pfs_enabled))" around calls to PS to avoid
  an extra call if PS is not enabled.
- Moved checking flag_global_instrumention before other flags
  to speed up the case when PS is not enabled.

To use:
- Compile with -DUSE_MY_LIKELY
- Change (with replace) all likely/unlikely to my_likely/my_/unlikely
  replace likely my_likely unlikely my_unlikely -- *c *h
- Start mysqld with -T
- run some test
- When mysqld has shut down cleanely, report will be on stderr

Added to:
- if (error)
- Lex
- sql_yacc.yy and sql_yacc_ora.yy
- In header files to alloc() calls
- Added thd argument to thd_net_is_killed()

It is test only (fix was done by Monty in ha_sequence::open by allocating ref)

            t1.pk IS NOT NULL where pk is a PRIMARY KEY

For equalites in the WHERE clause we create a keyuse array that contains the set of all equalities.
For each KEYUSE inside the keyuse array we have a field "null_rejecting"
which tells that the equality will not hold if either the left or right
hand side of the equality is NULL.
If the equality is NULL rejecting then we accordingly add a NOT NULL condition for the field present in
the item val(present in the KEYUSE struct) when we are doing ref access.

For the optimization of splitting with GROUP BY we always set the null_rejecting to TRUE and we are doing ref access on
the GROUP by field. This does create a problem when the equality is NOT NULL rejecting. This happens in this case as
in the equality we have the right hand side as t1.pk where pk is a PRIMARY KEY , hence it is NOT NULLABLE. So we should have
null rejecting set to FALSE for such a case.

The bug was the we copied the lock type to the underlying engine even when
external_lock failed.

log_sys_init(), log_buffer_extend(): Add TRASH_ALLOC() instrumentation

log_write_up_to(): Correctly calculate the byte offset.

The number of records in INFORMATION_SCHEMA.COLUMNS depends on the
build options, and could easily change when features are added.
We are not interested in the number of rows returned. The test was
originally added because of problem 15 reported in MDEV-13900
(testing for MDEV-11369 instant ADD COLUMN). The issue was an
assertion failure ut_ad(!rec_is_default_row(rec, index))
in lock_clust_rec_cons_read_sees(), because the 'default row' record
was not being properly ignored by the b-tree cursor.

The fix for this bug was automatically merged from 10.2.  However, that fix
was incomplete in 10.3.  This commit is for the additional changes that are
necessary in 10.3.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Fixed by removing the check of single lock in sequence insert and let MDL
code handle deadlock detection

MDEV-15060 Assertion in row_log_table_apply_op after instant ADD when the table is emptied during subsequent ALTER TABLE

During an online table rebuild, a table could be emptied and converted
from 'instant ADD' format to plain (pre-10.3) format. All online_log
records for rebuilding the table must be written and parsed in the
format of the table that existed at the start of the operation.

row_log_t::n_core_fields: A new field for recording index->n_core_fields
when online ALTER is initiated in row_log_allocate().

row_log_t::is_instant(): Determine if the log is in the instant format.
Only invoked by the row_log_table_ family of functions.

dict_index_t::get_n_nullable(): Remove is_instant() debug assertions.
Because a table can be converted to non-instant format during a
table-rebuilding ALTER TABLE, these assertions would be bogus when
executing row_log_table_apply().

rec_init_offsets_temp(): Add the parameter n_core for passing the
original index->n_core_fields.

rec_init_offsets_temp(): Add a 3-parameter variant.

rec_init_offsets_comp_ordinary(): Add the parameter n_core for
passing the index->n_core_fields.

MDEV-12266 changed dict_table_t::space to a pointer.
Displaying pointer values in error messages would be even more
meaningless than displaying numeric tablespace identifiers.

row_create_table_for_mysql(): Do not display table->space when
deleting the file fails. We cannot dereference table->space here,
because fil_delete_tablespace() would have freed the object.

fil_wait_crypt_bg_threads(): Do not display table->space. We could
display table->space_id here, but it should not really add any value,
because the table reference-counts have no direct connection to files
or tablespaces.

btr_pcur_store_position(): Assert that the 'default row' record never
is the only record in a page. (If that would happen, an empty
root page would be re-created in the non-instant format, not containing
the special record.) When the cursor is positioned on the page infimum,
never use the 'default row' as the BTR_PCUR_BEFORE reference.
(This is additional cleanup, not fixing the bug.)

rec_copy_prefix_to_buf(): When converting a record prefix to
the non-instant-add format, copy the original number of null flags.
Rename the variable instant_len to instant_omit, and introduce a
few more variables to make the code easiser to read.

Note: In purge, rec_copy_prefix_to_buf() is also used for storing the
persistent cursor position on a 'default row' record. The stored record
reference will be garbage, but row_search_on_row_ref() will do special
handling to reposition the cursor on the 'default row', based on
ref->info_bits.

innodb.dml_purge: Also cover the 'default row'.

MDEV-16071 Server crashed in innobase_build_col_map / prepare_inplace_alter_table_dict or Assertion `tuple' failed in dtuple_get_nth_field upon altering table with virtual column

- Virtual column should be considered during innobase_build_col_map() to find out
whether the field changed from NULL to NOT NULL.

- Added two new test case for it.

When a comma separator is missing between COMMENT fields, Spider ignores the
parameter values that are beyond the last expected parameter value.  There are
also some error messages that Spider does generate on COMMENT fields that are
incorrectly formed.

I have introduced additional infrastructure in Spider to fix these problems.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Cherry-Picked:
  Commit c10da98b on branch bb-10.3-MDEV-15698

When a comma separator is missing between COMMENT fields, Spider ignores the
parameter values that are beyond the last expected parameter value.  There are
also some error messages that Spider does generate on COMMENT fields that are
incorrectly formed.

I have introduced additional infrastructure in Spider to fix these problems.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Merged From:
  Branch bb-10.3-MDEV-15698

Remove unused InnoDB function parameters and functions.

i_s_sys_virtual_fill_table(): Do not allocate heap memory.

mtr_is_block_fix(): Replace with mtr_memo_contains().

mtr_is_page_fix(): Replace with mtr_memo_contains_page().

mysql_test_db.sql is in the srcdir

MDEV-15712: If remote server used by Spider table is unavailable, some operations hang for a long time

When an attempt to connect to the remote server fails, Spider retries to
connect to the remote server 1000 times or until the connection attempt
succeeds.  This is perceived as a hang if the remote server remains
unavailable.

I have introduced changes in Spider's table status handler to fix this problem.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Cherry-Picked:
  Commit 6ee6933a on branch bb-10.3-MDEV-15712

MDEV-15712: If remote server used by Spider table is unavailable, some operations hang for a long time

When an attempt to connect to the remote server fails, Spider retries to
connect to the remote server 1000 times or until the connection attempt
succeeds.  This is perceived as a hang if the remote server remains
unavailable.

I have introduced changes in Spider's table status handler to fix this problem.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Merged From:
  Branch bb-10.3-MDEV-15712.

Unexpected data truncation may occur when storing data to compressed blob
column having multi byte variable length character sets.

The reason was incorrect number of characters limit was enforced for
blobs.

Added --skip-test-db option to mysql_install_db. If specified, no test
database created and relevant grants issued.

Removed --skip-auth-anonymous-user option of mysql_install_db. Now it is
covered by --skip-test-db.

Dropped some Debian patches that did the same.

Removed unused make_win_bin_dist.1, make_win_bin_dist and
mysql_install_db.pl.in.

Implement innodb_flush_method as an enum parameter in Mariabackup,
instead of ignoring the option and hard-wiring it to a default value.

xb0xb.h: Remove. Only xtrabackup.cc refers to the enum parameters.

innodb_flush_method_names[], innodb_flush_method_typelib[]:
Define as non-static, so that mariabackup can share the definitions.

srv_file_flush_method: Change the type to ulong, to match the
assignment in init_one_value() and handle_options() in mariabackup.

Replace most use of #error. Some checks were impossible to
evaluate in the preprocessor due to the use of named
integer constants or enumerations.

The checks that used to be enabled by the flags
UNIV_AHI_DEBUG, UNIV_DDL_DEBUG, UNIV_DEBUG_FILE_ACCESSES
were already enabled in debug builds. So, there is no point
in setting these.

Only UNIV_ZIP_DEBUG is set independently of the debug build.

Allow WITH_INNODB_EXTRA_DEBUG to be set for non-debug builds as well.
Currently it only implies UNIV_ZIP_DEBUG, that is, extra validation
for operations on ROW_FORMAT=COMPRESSED tables.

page_zip_validate_low(): Allow the code to be built on non-debug server.
buf_LRU_block_remove_hashed(): Allow the code to be built without
WITH_INNODB_AHI.

- Removed test if HA_FT_WTYPE == HA_KEYTYPE_FLOAT as this never worked
  (HA_KEYTYPE_FLOAT is an enum)
- Define HA_FT_MAXLEN to 126 (was tested before but never defined)

Change all my_stcasecmp() calls that uses lexical keywords to use
lex_string_eq. This is faster as we only call strcasecmp() for
strings of different lengths.

Removed not used function lex_string_syseq()

- test-alter now correctly drops all columns
- test-alter has a new test that times adding columns in middle of table
- test-insert has a new test to check updates that doesn't change data
- test-insert: update_with_key_prefix didn't change data. Now fixed

The assertion would fail with the following trace:

rec_init_offsets_comp_ordinary(..., format=REC_LEAF_COLUMNS_ADDED)
rec_init_offsets()
rec_get_offsets_func()
rec_copy_prefix_to_dtuple()
dict_index_build_data_tuple()
btr_pcur_restore_position_func()

When btr_cur_store_position() had stored pcur->old_rec, the table
contained instantly added columns. The table was emptied
(dict_index_t::remove_instant() invoked) between the 'store' and 'restore'
operations, causing the assertion to fail. Here is a non-deterministic
test case to repeat the scenario:

	--source include/have_innodb.inc
	--connect (con1,localhost,root,,test)
	CREATE TABLE t1 (pk INT PRIMARY KEY) ENGINE = InnoDB;
	INSERT INTO t1 VALUES (0);
	ALTER TABLE t1 ADD COLUMN a INT;
	ALTER TABLE t1 ADD UNIQUE KEY (a);
	DELETE FROM t1;
	send INSERT INTO t1 VALUES (1,0),(2,0);
	--connection default
	DELETE FROM t1; # the assertion could fail here
	DROP TABLE t1;
	--disconnect con1

The fix is to normalize the pcur->old_rec so that when the
record prefix is stored, it will always be in the plain format.
This can be done, because the record prefix never includes any
instantly added columns. (It can only include key columns, which
can never be instantly added.)

rec_copy_prefix_to_buf(): Convert REC_STATUS_COLUMNS_ADDED to
REC_STATUS_ORDINARY format.

dict_index_copy_rec_order_prefix(): Avoid invoking
dict_index_get_n_unique_in_tree_nonleaf().

create_index(): Simplify code for creating SPATIAL or FULLTEXT index.

rec_copy_prefix_to_buf(): Skip the loop for SPATIAL INDEX.

Only allocate n_uniq elements for offsets, instead of index->n_fields.
(Statistics are never computed on spatial indexes, so we never need
to access more fields even in rec_copy_prefix_to_buf().)