This adds a TIME_MS column to SHOW FULL PROCESSLIST and
INFORMATION_SCHEMA.PROCESSLIST that works like the TIME column, but
in units of milliseconds with microsecond precision.
Note that this also changes behaviour of the existing TIME column. In
the MySQL server, the TIME column changes when a thread sets @TIMESTAMP.
This is contrary to documentation and also potentially confusing, so
could in any case be considered a bug. With this patch, to ensure
consistency between TIME and TIME_MS, setting @TIMESTAMP has no effect
on either value.
Add a test case for the TIME and TIME_MS columns.
Update existing test cases for changed behaviour.
Author: Percona
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
mysql-test/r/create.result:
Result file update.
mysql-test/r/information_schema.result:
Add test case.
Result file update (changed behaviour).
mysql-test/t/information_schema.test:
Add test case.
Adjust test case for changed behaviour.
mysql-test/t/not_embedded_server.test:
Update (commented-out) test case for newly added column.
sql/sql_show.cc:
Merge Percona microsec_process patch into MariaDB.
* Finished Monty and Jani's merge
* Some InnoDB tests still fail (because it's old xtradb code run against
newer testsuite). They are expected to go after mergning with the latest
xtradb.
Added (rewritten) patch from Percona to get extended statistics in slow.log:
- Added handling of 'set' variables to set_var.cc. Changed sql_mode to use this
- Added extra logging to slow log of 'Thread_id, Schema, Query Cache hit, Rows sent and Rows examined'
- Added optional logging to slow log, through log_slow_verbosity, of query plan statistics
- Added new user variables log_slow_rate_limit, log_slow_verbosity, log_slow_filter
- Added log-slow-file as synonym for 'slow-log-file', as most slow-log variables starts with 'log-slow'
- Added log-slow-time as synonym for long-query-time
Some trivial MyISAM optimizations:
- In prepare for drop, flush key blocks
- Don't call mi_lock_database if my_disable_locking is used
KNOWN_BUGS.txt:
Updated file to reflect MariaDB and not the Maria storage engine
README:
Updated file to reflect MariaDB
mysql-test/r/log_slow.result:
Test new options for slow query log
mysql-test/r/variables.result:
Updated result (old version cut of things at 79 characters)
mysql-test/t/log_slow.test:
Test new options for slow query log
sql/Makefile.am:
Added log_slow.h
sql/event_data_objects.cc:
Removed not needed test for enable_slow_log (is done when the flag is tested elsewhere)
sql/events.cc:
Use the general make_set() function instead of 'symbolic_mode_representation'
sql/filesort.cc:
Added status for used query plans
sql/log.cc:
Reset counters if no query_length (from Percona's patch; Not sure if needed, but can do no harm)
Added extra logging to slow log of 'Thread_id, Schema, Query Cache hit, Rows sent and Rows examined'
Added optional logging to slow log, through log_slow_verbosity, of query plan statistics
Fixed wrong test of error condition
sql/log_slow.h:
Defines and variables for log_slow_verbosity and log_slow_filter
sql/mysql_priv.h:
Include log_slow.h
sql/mysqld.cc:
Added new user variables log_slow_rate_limit, log_slow_verbosity, log_slow_filter
Added log-slow-file as synonym for 'slow-log-file', as most slow-log variables starts with 'log-slow'
Added log-slow-time as synonym for long-query-time
Added note that one should use log-slow-filter instead of log-slow-admin-statements
Updated comment from 'slow_query_log_file'
sql/set_var.cc:
Added long_slow_time as synonym for long_query_time
Added new user variables log_slow_rate_limit, log_slow_verbosity, log_slow_filter
dded handling of 'set' variables to set_var.cc. Changed sql_mode to use this
sql/set_var.h:
- Added handling of 'set' variables. Changed sql_mode to use this
sql/slave.cc:
Use global filter also for slaves
sql/sp_head.cc:
Simplify saving of general_slow_log state
Use the general make_set() function instead of 'symbolic_mode_representation'
sql/sql_cache.cc:
Added status for used query plans
sql/sql_class.cc:
Remember/restore query_plan_flags over complex statements
sql/sql_class.h:
Added variables to handle extended slow log statistics
sql/sql_parse.cc:
Added status for used query plans
Added test for filtering slow_query_log
sql/sql_select.cc:
Added status for used query plans
sql/sql_show.cc:
Use the general make_set() function instead of 'symbolic_mode_representation'
sql/strfunc.cc:
Report first error (not last) if something is wrong in a set
Removed compiler warning
storage/myisam/mi_extra.c:
In prepare for drop, flush key blocks (speed optimization)
storage/myisam/mi_locking.c:
Don't call mi_lock_database if my_disable_locking is used (speed optimization)
those keywords do nothing in 5.1 (they are meant for future versions, for example featuring the Maria engine)
so they are here removed from the syntax. Adding those keywords to future versions when needed is:
- WL#5034 "Add TRANSACTIONA=0|1 and PAGE_CHECKSUM=0|1 clauses to CREATE TABLE"
- WL#5037 "New ROW_FORMAT value for CREATE TABLE: PAGE"
mysql-test/r/create.result:
test that syntax is not accepted
mysql-test/t/create.test:
test that syntax is not accepted
sql/handler.cc:
remove ROW_FORMAT=PAGE
sql/handler.h:
Mark unused objects, but I don't remove them by fear of breaking any plugin which includes this file
(see also table.h)
sql/lex.h:
removing syntax
sql/sql_show.cc:
removing output of noise keywords in SHOW CREATE TABLE and INFORMATION_SCHEMA.TABLES
sql/sql_table.cc:
removing TRANSACTIONAL
sql/sql_yacc.yy:
removing syntax
sql/table.cc:
removing TRANSACTIONAL, PAGE_CHECKSUM. Their place in the frm file is not reclaimed,
for compatibility with older 5.1.
sql/table.h:
Mark unused objects, but I don't remove them by fear of breaking any plugin which includes this file
(and there are several engines which use the content TABLE_SHARE and thus rely on a certain binary
layout of this structure).
procedures causes crashes!
The problem of that bugreport was mostly fixed by the
patch for bug 38691.
However, attached test case focused on another crash or
valgrind warning problem: SHOW PROCESSLIST query accesses
freed memory of SP instruction that run in a parallel
connection.
Changes of thd->query/thd->query_length in dangerous
places have been guarded with the per-thread
LOCK_thd_data mutex (the THD::LOCK_delete mutex has been
renamed to THD::LOCK_thd_data).
sql/ha_myisam.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
Modification of THD::query/query_length has been guarded
with the a THD::set_query() method call/LOCK_thd_data
mutex.
Unnecessary locking with the global LOCK_thread_count
mutex has been removed.
sql/log_event.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
Modification of THD::query/query_length has been guarded
with the THD::set_query()) method call/LOCK_thd_data
mutex.
sql/slave.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
Modification of THD::query/query_length has been guarded
with the THD::set_query() method call/LOCK_thd_data mutex.
The THD::LOCK_delete mutex has been renamed to
THD::LOCK_thd_data.
sql/sp_head.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
Modification of THD::query/query_length has been guarded
with the a THD::set_query() method call/LOCK_thd_data
mutex.
sql/sql_class.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
The new THD::LOCK_thd_data mutex and THD::set_query()
method has been added to guard modifications of THD::query/
THD::query_length fields, also the Statement::set_statement()
method has been overloaded in the THD class.
The THD::LOCK_delete mutex has been renamed to
THD::LOCK_thd_data.
sql/sql_class.h:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
The new THD::LOCK_thd_data mutex and THD::set_query()
method has been added to guard modifications of THD::query/
THD::query_length fields, also the Statement::set_statement()
method has been overloaded in the THD class.
The THD::LOCK_delete mutex has been renamed to
THD::LOCK_thd_data.
sql/sql_insert.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
Modification of THD::query/query_length has been guarded
with the a THD::set_query() method call/LOCK_thd_data
mutex.
sql/sql_parse.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
Modification of THD::query/query_length has been guarded
with the a THD::set_query() method call/LOCK_thd_data mutex.
sql/sql_repl.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
The THD::LOCK_delete mutex has been renamed to
THD::LOCK_thd_data.
sql/sql_show.cc:
Bug #38816: kill + flush tables with read lock + stored
procedures causes crashes!
Inter-thread read of THD::query/query_length field has
been protected with a new per-thread LOCK_thd_data
mutex in the mysqld_list_processes function.
"create as select" (innodb table)
Problem: code constructing "CREATE TABLE..." statement
doesn't take into account that current database is not set
in some cases. That may lead to a server crash.
Fix: check if current database is set.
mysql-test/extra/binlog_tests/binlog.test:
Fix for bug#45998: database crashes when running
"create as select" (innodb table)
- test case.
mysql-test/suite/binlog/r/binlog_row_binlog.result:
Fix for bug#45998: database crashes when running
"create as select" (innodb table)
- test result.
sql/sql_show.cc:
Fix for bug#45998: database crashes when running
"create as select" (innodb table)
- added check if there's current database set.
Added privilege checking to SHOW CREATE TRIGGER code.
mysql-test/r/trigger_notembedded.result:
test result
mysql-test/t/trigger_notembedded.test:
test case
sql/sql_show.cc:
Added privilege checking to SHOW CREATE TRIGGER code.
The problem: described in the bug report.
The fix:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
client/mysql.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/ha_ndbcluster.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/ha_ndbcluster_binlog.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/handler.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/log.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/mysqld.cc:
removed unnecessary line
sql/parse_file.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_acl.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_base.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_db.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_delete.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_partition.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_rename.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_show.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_table.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
sql/sql_view.cc:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
as argument for strxnmov function
with gcc 4.3.2
Compiling MySQL with gcc 4.3.2 and later produces a number of
warnings, many of which are new with the recent compiler
versions.
This bug will be resolved in more than one patch to limit the
size of changesets. This is the second patch, fixing more
of the warnings.
with gcc 4.3.2
Compiling MySQL with gcc 4.3.2 and later produces a number of
warnings, many of which are new with the recent compiler
versions.
This bug will be resolved in more than one patch to limit the
size of changesets. This is the second patch, fixing more
of the warnings.
become negative
- merged the fix to 5.1
- extended to cover I_S.PROCESSLIST.TIME
- Changed the column type of I_S.PROCESSLIST.TIME from LOGNLONG
UNSIGNED
to LONG (to match the SHOW PROCESSLIST type)
- Added a test case
seems to become negative
THD::start_time has a dual meaning : it's either the time since the process
entered a given state or is the transaction time returned by e.g. NOW().
This causes problems, as sometimes THD::start_time may be set to a value
that is correct and needed when used as a base for NOW(), but these times
may be arbitrary (SET @@timestamp) or non-local (coming from the master
through the replication feed).
If one such non-local time is set there's no way to return a correct value
for e.g. SHOW PROCESSLIST or SELECT ... FROM INFORMATION_SCHEMA.PROCESSLIST.
Fixed by making the Time column in SHOW PROCESSLIST SIGNED LONG instead of
UNSIGNED LONG and doing the correct conversions.
Note that no reliable test suite can be constructed, since it would require
knowing the local time and can't be achieved by the means of the current test
suite.
sql/sql_show.cc:
Bug #22047: make the Time in SHOW PROCESSLIST LONG from
LONG UNSIGNED
print compact view name if the view belongs to the current database
mysql-test/r/information_schema_db.result:
result fix
mysql-test/r/mysqldump.result:
result fix
mysql-test/r/view_grant.result:
result fix
sql/sql_show.cc:
print compact view name if the view belongs to the current database
Changed context of Create routine to Databases.
mysql-test/r/grant.result:
result fix
mysql-test/r/sp.result:
result fix
sql/sql_show.cc:
Changed context of Create routine to Databases.
mysql-test/t/variables.test:
Reset delay_key_write, otherwise maria.maria test may fail
sql/set_var.cc:
Reset ha_open_options if one resets the delay_key_write variable.
Before there was no way to reset it without restarting mysqld, which caused some tests to fail
replace wild_case_compare with my_wildcmp which is multibyte safe function
mysql-test/r/lowercase_utf8.result:
test result
mysql-test/t/lowercase_utf8-master.opt:
test case
mysql-test/t/lowercase_utf8.test:
test case
sql/sql_show.cc:
replace wild_case_compare with my_wildcmp which is multibyte safe function
There were so many changes into mtr (this is the new mtr coming) that I rather
copied mtr from 6.0-main here (at least this one knows how to run Maria tests).
I also fixed suite/maria tests to be accepted by the new mtr.
mysys/thr_mutex.c:
adding DBUG_PRINT here, so that we can locate where the warning is issued.
- Remove bothersome warning messages. This change focuses on the warnings
that are covered by the ignore file: support-files/compiler_warnings.supp.
- Strings are guaranteed to be max uint in length
- Added braces around expressions with &&, ||, & and |
- Added empty line before ; for empty while and for loops
- Added () around if with assignments
- Removed const before function returning simple type
Changed BUILD scripts to not build with NDB
BUILD/SETUP.sh:
By default, don't build ndb with --max in Maria tree.
NDB is not kept up to date anyway in 5.1
client/mysql.cc:
Added braces around && to get rid of compiler warnings
sql/event_db_repository.cc:
Added braces around && to get rid of compiler warnings
sql/events.cc:
Added braces around && to get rid of compiler warnings
sql/field.cc:
Added braces around && to get rid of compiler warnings
Fixed for loops
sql/field.h:
Added braces around & to get rid of compiler warnings
sql/field_conv.cc:
Added braces around && to get rid of compiler warnings
Fixed bug when copying between DATETIME fields and strict dates are used
Removed not needeed else
sql/gstream.cc:
Added braces around && to get rid of compiler warnings
sql/ha_ndbcluster.cc:
Added braces around && to get rid of compiler warnings
Added {} to get rid of compiler warnings
sql/handler.cc:
Added braces around && to get rid of compiler warnings
sql/item.cc:
Added braces around && to get rid of compiler warnings
sql/item_cmpfunc.cc:
Added braces around && to get rid of compiler warnings
Removed some not needed space
sql/item_func.cc:
Added braces around && to get rid of compiler warnings
sql/item_strfunc.cc:
Added braces around && to get rid of compiler warnings
sql/item_subselect.cc:
Added braces around && to get rid of compiler warnings
sql/item_sum.cc:
Added braces around && to get rid of compiler warnings
sql/item_timefunc.cc:
Added braces around && to get rid of compiler warnings
sql/item_xmlfunc.cc:
Added empty line before ; for empty while and for loops
sql/log.cc:
Added braces around && to get rid of compiler warnings
sql/log_event.cc:
Added braces around && to get rid of compiler warnings
Removed not needed else
sql/log_event_old.cc:
Added braces around && to get rid of compiler warnings
sql/opt_range.cc:
Added braces around && to get rid of compiler warnings
sql/opt_sum.cc:
Added braces around && to get rid of compiler warnings
sql/set_var.cc:
Added empty line before ; for empty while and for loops
Added () around if with assignments
sql/slave.cc:
Added braces around && to get rid of compiler warnings
Added empty line before ; for empty while and for loops
sql/spatial.h:
Added braces around && to get rid of compiler warnings
sql/sql_acl.cc:
Added braces around && to get rid of compiler warnings
sql/sql_analyse.cc:
Added empty line before ; for empty while and for loops
sql/sql_base.cc:
Added braces around && to get rid of compiler warnings
sql/sql_connect.cc:
Added braces around && to get rid of compiler warnings
sql/sql_db.cc:
Added braces around && to get rid of compiler warnings
sql/sql_delete.cc:
Added braces around && to get rid of compiler warnings
sql/sql_help.cc:
Added empty line before ; for empty while and for loops
sql/sql_insert.cc:
Added braces around && to get rid of compiler warnings
Added () around if with assignments
sql/sql_lex.cc:
Cast char array references to uchar; Fixed wrong array referencing when using characters > ASCII 128 in SQL statments
Added empty line before ; for empty while and for loops
Trivial indent fixes
Added braces around && to get rid of compiler warnings
sql/sql_load.cc:
Added braces around && to get rid of compiler warnings
sql/sql_parse.cc:
Added braces around && to get rid of compiler warnings
sql/sql_partition.cc:
Added braces around && to get rid of compiler warnings
sql/sql_plugin.cc:
Fixed bug in detecing if option variable should be readonly
Added empty line before ; for empty while and for loops
sql/sql_prepare.cc:
Added braces around && to get rid of compiler warnings
sql/sql_select.cc:
Added braces around && to get rid of compiler warnings
Added () around if with assignments
Added empty line before ; for empty while and for loops
sql/sql_show.cc:
Added braces around && to get rid of compiler warnings
sql/sql_table.cc:
Added braces around && to get rid of compiler warnings
sql/sql_trigger.cc:
Added braces around && to get rid of compiler warnings
sql/sql_update.cc:
Added braces around && to get rid of compiler warnings
sql/sql_yacc.yy:
Added braces around && to get rid of compiler warnings
sql/table.cc:
Added braces around && to get rid of compiler warnings
sql/table.h:
Added braces around && to get rid of compiler warnings
sql/time.cc:
Added braces around && to get rid of compiler warnings
sql/tztime.cc:
Added braces around && to get rid of compiler warnings
sql/uniques.cc:
Added braces around && to get rid of compiler warnings
storage/federated/ha_federated.cc:
Fixed bug in testing of variable to ha_info() (Not critical)
storage/heap/ha_heap.cc:
Added braces around && to get rid of compiler warnings
storage/maria/ha_maria.cc:
Fixed bug: Mark that maria_log_dir_path is readonly
Added braces around && to get rid of compiler warnings
storage/ndb/include/ndbapi/NdbEventOperation.hpp:
Removed const before function returning simple type
storage/ndb/include/ndbapi/NdbOperation.hpp:
Removed const before function returning simple type
storage/ndb/src/ndbapi/Ndb.cpp:
Added empty line before ; for empty while and for loops
storage/ndb/src/ndbapi/NdbEventOperation.cpp:
Removed const before function returning simple type
storage/ndb/src/ndbapi/NdbEventOperationImpl.cpp:
Removed const before function returning simple type
storage/ndb/src/ndbapi/NdbEventOperationImpl.hpp:
Removed const before function returning simple type
storage/ndb/src/ndbapi/NdbRecAttr.cpp:
Added empty line before ; for empty while and for loops
storage/ndb/src/ndbapi/TransporterFacade.hpp:
Added braces around && to get rid of compiler warnings
Added global status variable 'Queries' which represents
total amount of queries executed by server including
statements executed by SPs.
note: It's old behaviour of 'Questions' variable.
mysql-test/r/status.result:
test result
mysql-test/t/status.test:
test case
sql/mysqld.cc:
Added global status variable 'Queries' which represents
total amount of queries executed by server including
statements executed by SPs.
note: It's old behaviour of 'Questions' variable.
sql/sql_show.cc:
Added global status variable 'Queries' which represents
total amount of queries executed by server including
statements executed by SPs.
note: It's old behaviour of 'Questions' variable.
sql/structs.h:
Added global status variable 'Queries' which represents
total amount of queries executed by server including
statements executed by SPs.
note: It's old behaviour of 'Questions' variable.
replace wild_case_compare with my_wildcmp which is multibyte safe function
mysql-test/r/lowercase_utf8.result:
test result
mysql-test/t/lowercase_utf8-master.opt:
test case
mysql-test/t/lowercase_utf8.test:
test case
sql/sql_show.cc:
replace wild_case_compare with my_wildcmp which is multibyte safe function
The problem is that we cannot insert new record into memory table
when table size exceeds max memory table size.
The fix is to use schema_table_store_record() function which
converts memory table into MyISAM in case of table size exceeding.
Note:
There is no test case for this bug, the reason is that
1. The code that was added already is checked(i.e. works) with existing tests
2. Correct work of schema_table_store_record() is checked with other test cases
(information_schema tests)
So new code is fully covered with existing test cases.
sql/mysql_priv.h:
make schema_table_store_record() function global
sql/sql_acl.cc:
The problem is that we cannot insert new record into memory table
when table size exceeds max memory table size.
The fix is to use schema_table_store_record() function which
converts memory table into MyISAM in case of table size exceeding.
sql/sql_show.cc:
make schema_table_store_record() function global
Static disabled plugins|engines and dynamic plugins which installed but disabled
are not visible in I_S PLUGINS|ENGINES tables because they are not stored into
global plugin array.
The fix: add such plugins|engines to plugin array with PLUGIN_IS_DISABLED status.
I_S.ENGINES 'Transactions', 'XA', 'Savepoints' fields have NULL value in this case.
mysql-test/r/warnings_engine_disabled.result:
test result
mysql-test/suite/funcs_1/r/is_columns_is.result:
result fix
mysql-test/suite/funcs_1/r/is_engines.result:
result fix
mysql-test/t/warnings_engine_disabled.test:
test case
sql/sql_plugin.cc:
store disabled plugins|engines into plugin array
sql/sql_plugin.h:
added PLUGIN_IS_DISABLED flag
sql/sql_show.cc:
added filling of 'engines'&'plugins' tables with disabled engines|plugins
Added KEY_BLOCK_SIZE option to I_S.TABLES.CREATE_OPTIONS field
mysql-test/r/information_schema.result:
test result
mysql-test/t/information_schema.test:
test case
sql/sql_show.cc:
Added KEY_BLOCK_SIZE option to I_S.TABLES.CREATE_OPTIONS field
mysql-test/r/myisam_data_pointer_size_func.result:
restore default value
mysql-test/r/partition_datatype.result:
test case fix
mysql-test/t/myisam_data_pointer_size_func.test:
restore default value
show default value for BIT field in printable format
mysql-test/r/type_bit.result:
Bug#35796 SHOW CREATE TABLE and default value for BIT field
test result
mysql-test/t/type_bit.test:
Bug#35796 SHOW CREATE TABLE and default value for BIT field
test case
sql/item.cc:
Bug#35796 SHOW CREATE TABLE and default value for BIT field
issue an error if BIN|HEX deafult value is empty value
(behaviour like for INT fields)
