Let TABLE_SHARE::tdc.free_tables, TABLE_SHARE::tdc.all_tables,
TABLE_SHARE::tdc.flushed and corresponding invariants be protected by
per-share TABLE_SHARE::tdc.LOCK_table_share instead of global LOCK_open.
Now if CREATE OR REPLACE fails but we have deleted a table already, we will generate a DROP TABLE in the binary log.
This fixes this issue.
In addition, for a failing CREATE OR REPLACE TABLE ... SELECT we don't generate a log of all the inserted rows, only the DROP TABLE.
I added code for not logging DROP TEMPORARY TABLE for tables where the CREATE TABLE was not logged. This code will be activated in 10.1
by removing the code protected by DONT_LOG_DROP_OF_TEMPORARY_TABLES.
mysql-test/suite/rpl/r/create_or_replace_mix.result:
More test cases
mysql-test/suite/rpl/r/create_or_replace_row.result:
More test cases
mysql-test/suite/rpl/r/create_or_replace_statement.result:
More test cases
mysql-test/suite/rpl/t/create_or_replace.inc:
More test cases
sql/log.cc:
Added binlog_reset_cache() to clear the binary log.
sql/log.h:
Added prototype
sql/sql_insert.cc:
If CREATE OR REPLACE TABLE ... SELECT fails:
- Don't log anything if nothing changed
- If table was deleted, log a DROP TABLE.
Remember if we table creation of temporary tables was logged.
sql/sql_table.cc:
Added log_drop_table()
Remember if we table creation of temporary tables was logged.
If CREATE OR REPLACE TABLE ... SELECT fails and a table was deleted, log a DROP TABLE.
sql/sql_table.h:
Added prototype
sql/sql_truncate.cc:
Remember if we table creation of temporary tables was logged.
sql/table.h:
Added table_creation_was_logged
This is port of fix for MySQL BUG#17647863.
revno: 5572
revision-id: jon.hauglid@oracle.com-20131030232243-b0pw98oy72uka2sj
committer: Jon Olav Hauglid <jon.hauglid@oracle.com>
timestamp: Thu 2013-10-31 00:22:43 +0100
message:
Bug#17647863: MYSQL DOES NOT COMPILE ON OSX 10.9 GM
Rename test() macro to MY_TEST() to avoid conflict with libc++.
Move TABLE::in_use out of LOCK_open.
This is done with assumtion that foreign threads accessing TABLE::in_use
will only need consistent value _after_ marking table for flush and purging
unused table instances. In this case TABLE::in_use will always point to a
valid thread object.
Previously FLUSH TABLES thread may wait for tables flushed subsequently by
concurrent threads which breaks the above assumption, e.g.:
open tables: t1 (version= 1)
thr1 (FLUSH TABLES): refresh_version++
thr1 (FLUSH TABLES): purge table cache
open tables: none
thr2 (SELECT * FROM t1): open tables: t1
open tables: t1 (version= 2)
thr2 (FLUSH TABLES): refresh_version++
thr2 (FLUSH TABLES): purge table cache
thr1 (FLUSH TABLES): wait for old tables (including t1 with version 2)
It is fixed so that FLUSH TABLES waits only for tables that were open
heretofore.
Using CREATE OR REPLACE TABLE is be identical to
DROP TABLE IF EXISTS table_name;
CREATE TABLE ...;
Except that:
* CREATE OR REPLACE is be atomic (now one can create the same table between drop and create).
* Temporary tables will not shadow the table name for the DROP as the CREATE TABLE tells us already if we are using a temporary table or not.
* If the table was locked with LOCK TABLES, the new table will be locked with the same lock after it's created.
Implementation details:
- We don't anymore open the to-be-created table during CREATE TABLE, which the original code did.
- There is no need to open a table we are planning to create. It's enough to check if the table exists or not.
- Removed some of duplicated code for CREATE IF NOT EXISTS.
- Give an error when using CREATE OR REPLACE with IF NOT EXISTS (conflicting options).
- As a side effect of the code changes, we don't anymore have to internally re-prepare prepared statements with CREATE TABLE if the table exists.
- Made one code path for all testing if log table are in use.
- Better error message if one tries to create/drop/alter a log table in use
- Added back disabled rpl_row_create_table test as it now seams to work and includes a lot of interesting tests.
- Added HA_LEX_CREATE_REPLACE to mark if we are using CREATE OR REPLACE
- Aligned CREATE OR REPLACE parsing code in sql_yacc.yy for TABLE and VIEW
- Changed interface for drop_temporary_table() to make it more reusable
- Changed Locked_tables_list::init_locked_tables() to work on the table object instead of the table list object. Before this it used a mix of both, which was not good.
- Locked_tables_list::unlock_locked_tables(THD *thd) now requires a valid thd argument. Old usage of calling this with 0 i changed to instead call Locked_tables_list::reset()
- Added functions Locked_tables_list:restore_lock() and Locked_tables_list::add_back_last_deleted_lock() to be able to easily add back a locked table to the lock list.
- Added restart_trans_for_tables() to be able to restart a transaction.
- DROP_ACL is required if one uses CREATE TABLE OR REPLACE.
- Added drop of normal and temporary tables in create_table_imp() if CREATE OR REPLACE was used.
- Added reacquiring of table locks in mysql_create_table() and mysql_create_like_table()
mysql-test/include/commit.inc:
With new code we get fewer status increments
mysql-test/r/commit_1innodb.result:
With new code we get fewer status increments
mysql-test/r/create.result:
Added testing of create or replace with timeout
mysql-test/r/create_or_replace.result:
Basic testing of CREATE OR REPLACE TABLE
mysql-test/r/partition_exchange.result:
New error message
mysql-test/r/ps_ddl.result:
Fewer reprepares with new code
mysql-test/suite/archive/discover.result:
Don't rediscover archive tables if the .frm file exists
(Sergei will look at this if there is a better way...)
mysql-test/suite/archive/discover.test:
Don't rediscover archive tables if the .frm file exists
(Sergei will look at this if there is a better way...)
mysql-test/suite/funcs_1/r/innodb_views.result:
New error message
mysql-test/suite/funcs_1/r/memory_views.result:
New error message
mysql-test/suite/rpl/disabled.def:
rpl_row_create_table should now be safe to use
mysql-test/suite/rpl/r/rpl_row_create_table.result:
Updated results after adding back disabled test
mysql-test/suite/rpl/t/rpl_create_if_not_exists.test:
Added comment
mysql-test/suite/rpl/t/rpl_row_create_table.test:
Added CREATE OR REPLACE TABLE test
mysql-test/t/create.test:
Added CREATE OR REPLACE TABLE test
mysql-test/t/create_or_replace-master.opt:
Create logs
mysql-test/t/create_or_replace.test:
Basic testing of CREATE OR REPLACE TABLE
mysql-test/t/partition_exchange.test:
Error number changed as we are now using same code for all log table change issues
mysql-test/t/ps_ddl.test:
Fewer reprepares with new code
sql/handler.h:
Moved things around a bit in a structure to get better alignment.
Added HA_LEX_CREATE_REPLACE to mark if we are using CREATE OR REPLACE
Added 3 elements to end of HA_CREATE_INFO to be able to store state to add backs locks in case of LOCK TABLES.
sql/log.cc:
Reimplemented check_if_log_table():
- Simpler and faster usage
- Can give error messages
This gives us one code path for allmost all error messages if log tables are in use
sql/log.h:
New interface for check_if_log_table()
sql/slave.cc:
More logging
sql/sql_alter.cc:
New interface for check_if_log_table()
sql/sql_base.cc:
More documentation
Changed interface for drop_temporary_table() to make it more reusable
Changed Locked_tables_list::init_locked_tables() to work on the table object instead of the table list object. Before this it used a mix of both, which was not good.
Locked_tables_list::unlock_locked_tables(THD *thd) now requires a valid thd argument. Old usage of calling this with 0 i changed to instead call Locked_tables_list::reset()
Added functions Locked_tables_list:restore_lock() and Locked_tables_list::add_back_last_deleted_lock() to be able to easily add back a locked table to the lock list.
Check for command number instead of open_strategy of CREATE TABLE was used.
Added restart_trans_for_tables() to be able to restart a transaction. This was needed in "create or replace ... select" between the drop table and the select.
sql/sql_base.h:
Added and updated function prototypes
sql/sql_class.h:
Added new prototypes to Locked_tables_list class
Added extra argument to select_create to avoid double call to eof() or send_error()
- I needed this in some edge case where the table was not created against expections.
sql/sql_db.cc:
New interface for check_if_log_table()
sql/sql_insert.cc:
Remember position to lock information so that we can reaquire table lock for LOCK TABLES + CREATE OR REPLACE TABLE SELECT. Later add back the lock by calling restore_lock().
Removed one not needed indentation level in create_table_from_items()
Ensure we don't call send_eof() or abort_result_set() twice.
sql/sql_lex.h:
Removed variable that I temporarly added in an earlier changeset
sql/sql_parse.cc:
Removed old test code (marked with QQ)
Ensure that we have open_strategy set as TABLE_LIST::OPEN_STUB in CREATE TABLE
Removed some IF NOT EXISTS code as this is now handled in create_table_table_impl().
Set OPTION_KEEP_LOGS later. This code had to be moved as the test for IF EXISTS has changed place.
DROP_ACL is required if one uses CREATE TABLE OR REPLACE.
sql/sql_partition_admin.cc:
New interface for check_if_log_table()
sql/sql_rename.cc:
New interface for check_if_log_table()
sql/sql_table.cc:
New interface for check_if_log_table()
Moved some code in mysql_rm_table() under a common test.
- Safe as temporary tables doesn't have statistics.
- !is_temporary_table(table) test was moved out from drop_temporary_table() and merged with upper level code.
- Added drop of normal and temporary tables in create_table_imp() if CREATE OR REPLACE was used.
- Added reacquiring of table locks in mysql_create_table() and mysql_create_like_table()
- In mysql_create_like_table(), restore table->open_strategy() if it was changed.
- Re-test if table was a view after opening it.
sql/sql_table.h:
New prototype for mysql_create_table_no_lock()
sql/sql_yacc.yy:
Added syntax for CREATE OR REPLACE TABLE
Reuse new code for CREATE OR REPLACE VIEW
sql/table.h:
Added name for enum type
sql/table_cache.cc:
More DBUG
- Added MALLOC_LIBRARY variable to hold name of malloc library
- Back ported valgrind related fixes from jemalloc 3.4.1 to the included jemalloc 3.3.1
- Renamed bitmap_init() and bitmap_free() to my_bitmap_init() and my_bitmap_free() to avoid clash with jemalloc 3.4.1
- Use option --soname-synonyms=somalloc=NON to valgrind when using jemalloc
- Show version related variables in mysqld --help
-- Added SHOW_VALUE_IN_HELP marker
Increased back_log to 150 as the original value was a bit too small
CMakeLists.txt:
Added MALLOC_LIBRARY variable to hold name of malloc library
cmake/jemalloc.cmake:
Added MALLOC_LIBRARY variable to hold name of malloc library
config.h.cmake:
Added MALLOC_LIBRARY variable to hold name of malloc library
extra/jemalloc/ChangeLog:
Updates changelog
extra/jemalloc/include/jemalloc/internal/arena.h:
Backported valgrind fixes from jemalloc 3.4.1
extra/jemalloc/include/jemalloc/internal/jemalloc_internal.h.in:
Backported valgrind fixes from jemalloc 3.4.1
extra/jemalloc/include/jemalloc/internal/private_namespace.h:
Backported valgrind fixes from jemalloc 3.4.1
extra/jemalloc/include/jemalloc/internal/tcache.h:
Backported valgrind fixes from jemalloc 3.4.1
extra/jemalloc/src/arena.c:
Backported valgrind fixes from jemalloc 3.4.1
include/my_bitmap.h:
Renamed bitmap_init() and bitmap_free() to my_bitmap_init() and my_bitmap_free() to avoid clash with jemalloc 3.4.1
mysql-test/mysql-test-run.pl:
Use option --soname-synonyms=somalloc=NON to valgrind when using jemalloc
mysql-test/valgrind.supp:
Supression of memory leak in OpenSuse 12.3
mysys/my_bitmap.c:
Renamed bitmap_init() and bitmap_free() to my_bitmap_init() and my_bitmap_free()
sql/ha_ndbcluster_binlog.cc:
Renames
sql/ha_ndbcluster_cond.h:
Renames
sql/ha_partition.cc:
Renames
sql/handler.cc:
Renames
sql/item_subselect.cc:
Renames
sql/log_event.cc:
Renames
sql/log_event_old.cc:
Renames
sql/mysqld.cc:
Renames
Show version related variables in mysqld --help
sql/opt_range.cc:
Renames
sql/opt_table_elimination.cc:
Renames
sql/partition_info.cc:
Renames
sql/rpl_injector.h:
Renames
sql/set_var.h:
Renames
sql/slave.cc:
Renames
sql/sql_bitmap.h:
Renames
sql/sql_insert.cc:
Renames
sql/sql_lex.h:
Renames
sql/sql_parse.cc:
Renames
sql/sql_partition.cc:
Renames
sql/sql_select.cc:
Renames
sql/sql_show.cc:
Renames
sql/sql_update.cc:
Renames
sql/sys_vars.cc:
Show version related variables in mysqld --help
sql/sys_vars.h:
Added SHOW_VALUE_IN_HELP marker for variables that should be shown in --help
sql/table.cc:
Renames
sql/table.h:
Removed not used bitmap_init_value
storage/connect/ha_connect.cc:
Removed compiler warning
storage/maria/ma_open.c:
Renames
unittest/mysys/bitmap-t.c:
Renames
- tc_acquire_table and tc_release_table do not access
TABLE_SHARE::tdc.used_tables anymore
- in tc_acquire_table(): release LOCK_tdc after we relase LOCK_open
(saves a few CPU cycles in critical section)
- in tc_release_table(): if we reached table cache threshold, evict
to-be-released table without moving it to unused_tables. unused_tables
must be empty at this point.
- Character set code & tests from Alexander Barkov
- Integration with ALTER TABLE, REPAIR and open_table from Monty
The problem was that MySQL 5.6 added some croatian and vitanamese character set collations that are incompatible with MariaDB.
The fix is to move the MariaDB conflicting collation numbers out of the region that MySQL is likely to use.
mysql_upgrade, REPAIR TABLE or ALTER TABLE will fix the collations.
If one tries to access and old incompatible table, one will get the error "Table upgrade required...."
After this patch, MariaDB supports all the MySQL character set collations and the old MariaDB croatian collations, which are closer to the latest standard than the MySQL versions.
New character sets:
ucs2_croatian_mysql561_uca_ci
utf8_croatian_mysql561_uca_ci
utf16_croatian_mysql561_uca_ci
utf32_croatian_mysql561_uca_ci
utf8mb4_croatian_mysql561_uca_ci
Other things:
- Fixed some compiler warnings
- mysql_upgrade prints information about repaired tables.
- Increased version number
VERSION:
Increased VERSION number
client/mysqlcheck.c:
Print repaired table name when using --verbose
include/m_ctype.h:
Add new MariaDB collation regions that are not likely to conflict with MySQL
include/my_base.h:
Added flag to detect if table was opened for ALTER TABLE
mysql-test/r/ctype_ldml.result:
Updated result
mysql-test/r/ctype_uca.result:
Updated result
mysql-test/r/ctype_upgrade.result:
Updated result
mysql-test/r/ctype_utf16_uca.result:
Updated result
mysql-test/r/ctype_utf32_uca.result:
Updated result
mysql-test/r/ctype_utf8mb4_uca.result:
Updated result
mysql-test/std_data/ctype_upgrade:
Test files for testing upgrading of conflicting collations
mysql-test/suite/engines/funcs/r/db_alter_collate_ascii.result:
New collations added
mysql-test/suite/engines/funcs/r/db_alter_collate_utf8.result:
New collations added
mysql-test/suite/innodb/r/innodb_ctype_ldml.result:
Updated test result
mysql-test/suite/innodb/t/innodb_ctype_ldml.test:
Updated test result
mysql-test/suite/plugins/r/show_all_plugins.result:
Updated version number
mysql-test/suite/roles/create_and_drop_role_invalid_user_table.result:
Updated version number
mysql-test/t/ctype_ldml.test:
Updated test
mysql-test/t/ctype_uca.test:
Testing of new collations
mysql-test/t/ctype_upgrade.test:
Testing of upgrading tables with old collations
The test ensures that:
- We will get an error if we try to open a table with old collations.
- CHECK TABLE will detect that the table needs to be upgraded.
- ALTER TABLE and REPAIR will fix the table.
- mysql_upgrade works as expected
mysql-test/t/ctype_utf16_uca.test:
Testing of new collations
mysql-test/t/ctype_utf32_uca.test:
Testing of new collations
mysql-test/t/ctype_utf8mb4_uca.test:
Testing of new collations
mysys/charset-def.c:
Added new character sets
mysys/charset.c:
Always give an error, if requested, if a character set didn't exist
sql/handler.cc:
- Added upgrade_collation() to check if collation is compatible with old version
- check_collation_compatibility() checks if we are using an old collation from MariaDB 5.5 or MySQL 5.6
- ha_check_for_upgrade() returns HA_ADMIN_NEEDS_ALTER if we have an incompatible collation
sql/handler.h:
Added new prototypes
sql/sql_table.cc:
- Mark that tables are opened for ALTER TABLE
- If table needs to be upgraded, ensure we are not using online alter table.
sql/table.cc:
- If we are using an old incompatible collation, change to use the new one and mark table as incompatible.
- Give an error if we try to open an incompatible table.
sql/table.h:
Added error that table needs to be rebuild
storage/connect/ha_connect.cc:
Fixed compiler warning
strings/ctype-uca.c:
New character sets
Other fix of maybe_null problem and revert of revno: 3608 "MDEV-3873 & MDEV-3876 & MDEV-3912 : Wrong result (extra rows) with ALL subquery from a MERGE view."
ORDER BY does not work
Use "dynamic" row format (instead of "block") for MARIA internal
temporary tables created for cursors.
With "block" row format MARIA may shuffle rows, with "dynamic" row
format records are inserted sequentially (there are no gaps in data
file while we fill temporary tables).
This is needed to preserve row order when scanning materialized cursors.
When a non-nullable datetime field is used under an IS NULL predicate
of the WHERE condition in a query with outer joins the remove_eq_conds
function should check whether this field belongs to an inner table
of any outer join that can be, in a general case, a nested outer join.
Following variables do not require LOCK_open protection anymore:
- table_def_cache (renamed to tdc_hash) is protected by rw-lock
LOCK_tdc_hash;
- table_def_shutdown_in_progress doesn't need LOCK_open protection;
- last_table_id use atomics;
- TABLE_SHARE::ref_count (renamed to TABLE_SHARE::tdc.ref_count)
is protected by TABLE_SHARE::tdc.LOCK_table_share;
- TABLE_SHARE::next, ::prev (renamed to tdc.next and tdc.prev),
oldest_unused_share, end_of_unused_share are protected by
LOCK_unused_shares;
- TABLE_SHARE::m_flush_tickets (renamed to tdc.m_flush_tickets)
is protected by TABLE_SHARE::tdc.LOCK_table_share;
- refresh_version (renamed to tdc_version) use atomics.
Temorary fix for a number of replication tests (rpl.rpl_temp_table_mix_row
rpl.rpl_trunc_temp rpl.rpl_current_user rpl.rpl_gtid_master_promote):
- THD::decide_logging_format() should not assume that mysql.gtid_slave_pos is
a non-replicated table. This used to cause unintended behavior for COMMIT
statement: replication would switch to row-based, etc.
The question of what should be done when a user issues a statement that
explicitly modifies mysql.gtid_slave_pos table remains open.
includes:
* remove some remnants of "Bug#14521864: MYSQL 5.1 TO 5.5 BUGS PARTITIONING"
* introduce LOCK_share, now LOCK_ha_data is strictly for engines
* rea_create_table() always creates .par file (even in "frm-only" mode)
* fix a 5.6 bug, temp file leak on dummy ALTER TABLE
Includes 5.6 changesets for:
*****
Fix for BUG#13489996 valgrind:conditional jump or move depends on uninitialised values-field_blob.
blob_ptr_size was not initialized properly: remove this variable.
*****
Bug#14021323 CRASH IN FIELD::SET_NULL WHEN INSERTING ROWS TO NEW TABLE
*****
revno: 4559
committer: Marc Alff <marc.alff@oracle.com>
branch nick: mysql-5.6-bug14741537-v4
timestamp: Thu 2012-11-08 22:40:31 +0100
message:
Bug#14741537 - MYSQL 5.6, GTID AND PERFORMANCE_SCHEMA
Before this fix, statements using performance_schema tables:
- were marked as unsafe for replication,
- did cause warnings during execution,
- were written to the binlog, either in STATEMENT or ROW format.
When using replication with the new GTID feature,
unsafe warnings are elevated to errors,
which prevents to use both the performance_schema and GTID together.
The root cause of the problem is not related to raising warnings/errors
in some special cases, but deeper: statements involving the performance
schema should not even be written to the binary log in the first place,
because the content of the performance schema tables is 'local' to a server
instance, and may differ greatly between nodes in a replication
topology.
In particular, the DBA should be able to configure (INSERT, UPDATE, DELETE)
or flush (TRUNCATE) performance schema tables on one node,
without affecting other nodes.
This fix introduces the concept of a 'non-replicated' or 'local' table,
and adjusts the replication logic to ignore tables that are not replicated
when deciding if or how to log a statement to the binlog.
Note that while this issue was detected using the performance_schema,
other tables are also affected by the same problem.
This fix define as 'local' the following tables, which are then never
replicated:
- performance_schema.*
- mysql.general_log
- mysql.slow_log
- mysql.slave_relay_log_info
- mysql.slave_master_info
- mysql.slave_worker_info
Existing behavior for information_schema.* is unchanged by this fix,
to limit the scope of changes.
Coding wise, this fix implements the following changes:
1)
Performance schema tables are not using any replication flags,
since performance schema tables are not replicated.
2)
In open_table_from_share(),
tables with no replication capabilities (performance_schema.*),
tables with TABLE_CATEGORY_LOG (logs)
and tables with TABLE_CATEGORY_RPL_INFO (replication)
are marked as non replicated, with TABLE::no_replicate
3)
A new THD member, THD::m_binlog_filter_state,
indicate if the current statement is written to the binlog
(normal cases for most statements), or is to be discarded
(because the statements affects non replicated tables).
4)
In THD::decide_logging_format(), the replication logic
is changed to take into account non replicated tables.
Statements that affect only non replicated tables are
executed normally (no warning or errors), but not written
to the binlog.
Statements that affect (i.e., write to) a replicated table
while also using (i.e., reading from or writing to) a non replicated table
are executed normally in MIXED and ROW binlog format,
and cause a new error in STATEMENT binlog format.
THD::decide_logging_format() uses THD::m_binlog_filter_state
to indicate if a statement is to be ignored, when writing to
the binlog.
5)
In THD::binlog_query(), statements marked as ignored
are not written to the binary log.
6)
For row based replication, the existing test for 'table->no_replicate',
has been moved from binlog_log_row() to check_table_binlog_row_based().
Implement discovery of table non-existence, and related changes:
1. Split GTS_FORCE_DISCOVERY (that was meaning two different things in
two different functions) into GTS_FORCE_DISCOVERY and GTS_USE_DISCOVERY.
2. Move GTS_FORCE_DISCOVERY implementation into open_table_def().
3. In recover_from_failed_open() clear old errors *before* discovery,
not after successful discovery. The final error should come
from the discovery.
4. On forced discovery delete table .frm first. Discovery will write
a new one, if desired.
5. If the frm file exists, but not the table in the engine, force
rediscovery if the engine supports it.
1. default db type for partitions was stored as 1-byte DB_TYPE code,
which doesn't work for dynamically generated codes.
2. storage engine plugin for default db type wasn't locked at all,
which could trivially crash for dynamic plugins.
Now the storage engine name is stored in the extra2 section,
and the plugin is correctly locked.
1. DROP DATABASE should use ha_discover_table_names(), not look at .frm files.
2. filename_to_tablename() also encodes temp file names #sql- -> #mysql50##sql
3. no special treatment for #sql- files, no TABLE_LIST::internal_tmp_table
4. discover also table file names, that start from #
WITH COMPOSITE KEY COLUMNS
Problem:-
While running a SELECT query with several AGGR(DISTINCT) function
and these are referring to different field of same composite key,
Returned incorrect value.
Analysis:-
In a table, where we have composite key like (a,b,c)
and when we give a query like
select COUNT(DISTINCT b), SUM(DISTINCT a) from ....
here, we first make a list of items in Aggr(distinct) function
(which is a, b), where order of item doesn't matter.
and then we see, whether we have a composite key where the prefix
of index columns matches the items of the aggregation function.
(in this case we have a,b,c).
if yes, so we can use loose index scan and we need not perform
duplicate removal to distinct in our aggregate function.
In our table, we traverse column marked with <-- and get the result as
(a,b,c) count(distinct b) sum(distinct a)
treated as count b treated as sum(a)
(1,1,2)<-- 1 1
(1,2,2)<-- 1++=2 1+1=2
(1,2,3)
(2,1,2)<-- 2++=3 1+1+2=4
(2,2,2)<-- 3++=4 1+1+2+2=6
(2,2,3)
result will be 4,6, but it should be (2,3)
As in this case, our assumption is incorrect. If we have
query like
select count(distinct a,b), sum(distinct a,b)from ..
then we can use loose index scan
Solution:-
In our query, when we have more then one aggr(distinct) function
then they should refer to same fields like
select count(distinct a,b), sum(distinct a,b) from ..
-->we can use loose scan index as both aggr(distinct) refer to same fields a,b.
If they are referring to different field like
select count(distinct a), sum(distinct b) from ..
-->will not use loose scan index as both aggr(distinct) refer to different fields.
Merge of 10.0-mdev26 feature tree into 10.0-base.
Global transaction ID is prepended to each event group in the binlog.
Slave connect can request to start from GTID position instead of specifying
file name/offset of master binlog. This facilitates easy switch to a new
master.
Slave GTID state is stored in a table mysql.rpl_slave_state, which can be
InnoDB to get crash-safe slave state.
GTID includes a replication domain ID, allowing to keep track of distinct
positions for each of multiple masters.
