- Removed dead code
- Renamed a function
- Removed a parameter that not needed.
- Corrected comments

in the tree bb-10.4-mdev7486

The crash was caused because of the similar problem as in mdev-16765:
Item_cond::excl_dep_on_group_fields_for_having_pushdown() was missing.

           in the tree bb-10.4-mdev7486

The crash was caused because after merge of bb-10.4-mdev7486 and
10.4 branches changes for mdev-16727 were missing.

It was allowed to push UDF functions and that caused a crash.
To fix it it was forbidden to push UDF functions from HAVING into WHERE.

Condition can be pushed from the HAVING clause into the WHERE clause
if it depends only on the fields that are used in the GROUP BY list
or depends on the fields that are equal to grouping fields.
Aggregate functions can't be pushed down.

How the pushdown is performed on the example:

SELECT t1.a,MAX(t1.b)
FROM t1
GROUP BY t1.a
HAVING (t1.a>2) AND (MAX(c)>12);

=>

SELECT t1.a,MAX(t1.b)
FROM t1
WHERE (t1.a>2)
GROUP BY t1.a
HAVING (MAX(c)>12);

The implementation scheme:

1. Extract the most restrictive condition cond from the HAVING clause of
   the select that depends only on the fields that are used in the GROUP BY
   list of the select (directly or indirectly through equalities)
2. Save cond as a condition that can be pushed into the WHERE clause
   of the select
3. Remove cond from the HAVING clause if it is possible

The optimization is implemented in the function
st_select_lex::pushdown_from_having_into_where().

New test file having_cond_pushdown.test is created.

Field_str::is_equal(): Do not allow instant conversions between
BIT (which is stored big-endian) and integer types (which can
be stored big-endian or little-endian, depending on storage engine).

row_sel_field_store_in_mysql_format_func(): Properly extend
narrower integer and DATA_FIXBINARY values to the current format.
DATA_FIXBINARY was incorrectly padded with 0x20 instead of 0.

In tests that directly write InnoDB data file pages,
compute the innodb_checksum_algorithm=crc32 checksums,
instead of writing the 0xdeadbeef value used by
innodb_checksum_algorithm=none. In this way, these tests
will not cause failures when executing
./mtr --mysqld=--loose-innodb-checksum-algorithm=strict_crc32

1. Renaming Type_handler_json to Type_handler_json_longtext
   There will be other JSON handlers soon, e.g. Type_handler_json_varchar.

2. Making the code more symmetric for data types:

- Adding a new virtual method
  Type_handler::Column_definition_validate_check_constraint()
- Moving JSON-specific code from sql_yacc.yy to
  Type_handler_json_longtext::Column_definition_validate_check_constraint()

3. Adding new files sql_type_json.cc and sql_type_json.h
   and moving Type_handler+JSON related code into these files.

instant_alter_column_possible(): Add the other MDEV-17459 work-around
condition. The existence of fulltext indexes only prevents instant
DROP COLUMN or changing the order of columns. Other forms of instant
ALTER TABLE are no problem.

Before commit 4e7ee166 that merged
the MDEV-18295 fix from 10.3, the work-around of MDEV-17459 in
instant_alter_column_possible() was categorically refusing any
ALGORITHM=INSTANT if any FULLTEXT INDEX was present. After that commit,
a related condition was only present in prepare_inplace_alter_table_dict()
but not in the other callers of instant_alter_column_possible().

Fix some of the galera_sr suite test failures.
Remove tests that are not going to be run because required
feature is not supported.

	modified:   mysql-test/suite/galera_sr/disabled.def
	deleted:    mysql-test/suite/galera_sr/r/GCF-574.result
	modified:   mysql-test/suite/galera_sr/r/galera_sr_cc_slave.result
	modified:   mysql-test/suite/galera_sr/r/galera_sr_kill_all_norecovery.result
	modified:   mysql-test/suite/galera_sr/r/galera_sr_load_data.result
	deleted:    mysql-test/suite/galera_sr/r/galera_sr_sbr.result
	modified:   mysql-test/suite/galera_sr/r/mysql-wsrep-features#148.result
	deleted:    mysql-test/suite/galera_sr/r/mysql-wsrep-features#29.result
	deleted:    mysql-test/suite/galera_sr/t/GCF-574.test
	modified:   mysql-test/suite/galera_sr/t/galera_sr_cc_slave.test
	modified:   mysql-test/suite/galera_sr/t/galera_sr_kill_all_norecovery.cnf
	modified:   mysql-test/suite/galera_sr/t/galera_sr_kill_all_norecovery.test
	modified:   mysql-test/suite/galera_sr/t/galera_sr_load_data.test
	deleted:    mysql-test/suite/galera_sr/t/galera_sr_sbr.test
	modified:   mysql-test/suite/galera_sr/t/mysql-wsrep-features#148.test
	deleted:    mysql-test/suite/galera_sr/t/mysql-wsrep-features#29.test

dtype_is_string_type(), dtype_is_binary_string_type(),
dtype_is_non_binary_string_type(): Define as inline functions that
return bool, not ibool.

Also adjusted some test files.

The assertion happens under BACKUP STAGE BLOCK_COMMIT, when a DDL on a
temporary table (#sql-xxx) is found.

Apparently, assumption that all DDLs are blocked under FTWRL does not
hold for BACKUP STAGE, and temporary tables can still have ALTERs

The fix is to relax the assertion, and only check for opt_no_lock if
backup is *really* inconsistent, i.e either optimized DDL or CREATE/RENAME
are done on the tables that were not skipped during backup.

Allow ALGORITHM=INSTANT (or avoid touching any data)
when changing the collation, or in some cases, the character set,
of a non-indexed CHAR or VARCHAR column. There is no penalty
for subsequent DDL or DML operations, and compatibility with
older MariaDB versions will be unaffected.

Character sets may be changed when the old encoding is compatible
with the new one. For example, changing from ASCII to anything
ASCII-based, or from 3-byte to 4-byte UTF-8 can sometimes be
performed instantly.

This is joint work with Eugene Kosov.
The test cases as well as ALTER_CONVERT_TO, charsets_are_compatible(),
Type_handler::Charsets_are_compatible() are his work.
The Field_str::is_equal(), Field_varstring::is_equal() and
the InnoDB changes were mostly rewritten by me due to conflicts
with MDEV-15563.

Limitations:

Changes of indexed columns will still require
ALGORITHM=COPY. We should allow ALGORITHM=NOCOPY and allow
the indexes to be rebuilt inside the storage engine,
without copying the entire table.

Instant column size changes (in bytes) are not supported by
all storage engines.

Instant CHAR column changes are only allowed for InnoDB
ROW_FORMAT=REDUNDANT. We could allow this for InnoDB
when the CHAR internally uses a variable-length encoding,
say, when converting from 3-byte UTF-8 to 4-byte UTF-8.

Instant VARCHAR column changes are allowed for InnoDB
ROW_FORMAT=REDUNDANT, and for others only if the size
in bytes does not change from 128..255 bytes to more
than 256 bytes.

Inside InnoDB, this slightly changes the way how MDEV-15563
works and fixes the result of the innodb.instant_alter_extend test.
We change the way how ALTER_COLUMN_EQUAL_PACK_LENGTH_EXT
is handled. All column extension, type changes and renaming
now go through a common route, except when ctx->is_instant()
is in effect, for example, instant ADD or DROP COLUMN has
been initiated. Only in that case we will go through
innobase_instant_try() and rewrite all column metadata.

get_type(field, prtype, mtype, len): Convert a SQL data type into
InnoDB column metadata.

innobase_rename_column_try(): Remove the update of SYS_COLUMNS.

innobase_rename_or_enlarge_column_try(): New function,
replacing part of innobase_rename_column_try() and all of
innobase_enlarge_column_try(). Also changes column types.

innobase_rename_or_enlarge_columns_cache(): Also change
the column type.

move account options from LEX to Account_options structure
namely, mqh and ssl_*

Also, use LEX_CSTRING for ssl_*/x509_* strings and move
setting of ACL_USER::account_locked where it belongs

Add server support for user account locking.
This patch extends the ALTER/CREATE USER statements for
denying a user's subsequent login attempts:
  ALTER USER
    user [, user2] ACCOUNT [LOCK | UNLOCK]
  CREATE USER
    user [, user2] ACCOUNT [LOCK | UNLOCK]
The SHOW CREATE USER statement was updated to display the
locking state of an user.

Closes #1006

fix mysql_fix_privilege_tables to look for the `user` table in the
correct schema when deciding whether to convert it to `global_priv` table

make related tests a bit more verbose

Too easy to abuse. One tends to use it even when
microseconds are not needed and will be ignored.

Cleanup wsrep_schema and remove all references to wsrep_thd_pool

WSREP debug log levels support

* Removed all references related to wsrep_thd_pool (which was removed)

* Removed unused declarations in wsrep_schema.h

* The following would result invalid reads in
  Wsrep_schema::replay_transaction():
  ```
  frag_table->field[4]->val_str(&buf);

  Wsrep_schema_impl::end_index_scan(frag_table);
  Wsrep_schema_impl::finish_stmt(thd);
  ret= wsrep_apply_events(thd, rli, buf.c_ptr_safe(), buf.length());
  ```

  because `buf` was accessed after closing the table. The fix is to
  perform storage reads using a different THD.

* In Wsrep_schema::recover_sr_transactions(), cluster_table was opened
  for write, however it is only read here. And frag_table was opened
  for read, wereas write is potentially needed.
  Also, avoid copy caused by String::c_ptr() to zero terminate the c
  string, use c_ptr_quick instead.

Due to inconsistent usage of different cost models to calculate
the cost of ref accesses we have to make the calculation of the
gain promising by usage a range filter more complex.

Commit 22feb179 broke the build
with performance_schema disabled.

dict_col_t::same_charset(): An auxiliary function to
dict_col_t::same_format(). Determine if two non-binary string
columns have the same character set.

Remove 'register' quantifer from args too.

This was added in 29fa7252 (in 2000) and nothing defines
NEW_HASH_FUNCTION. A low collision is the wrong tradeoff,
it should be focused on throughput.

d405bee0 shows the existing function
is pretty cpu intensive and needs to be improved as well.

Global variable wsrep_debug now can be used to filter wsrep-lib messages based on debug level provided.
Type of wsrep_debug is now set to be unsigned int, so tests and configuration files changed accordingly.

When creating a field of type JSON, it will be automatically
converted to TEXT with CHECK (json_valid(`a`)), if there wasn't any
previous check for the column.

Additional things:
- Added two bug fixes that was found while testing JSON. These bug
  fixes has also been pushed to 10.3 (with a test case), but as they
  where minimal and needed to get this task done and tested, the fixes
  are repeated here.
  - CREATE TABLE ... SELECT drops constraints for columns that
    are both in the create and select part.
  - If one has both a default expression and check constraint for a
    column, one can get the error "Expression for field `a` is refering
    to uninitialized field `a`.
- Removed some duplicate MYSQL_PLUGIN_IMPORT symbols

Fixing failures of federated test on 32-bit platforms