Discovered this while working on MDEV-34720: test_if_cheaper_ordering()
uses rec_per_key, while the original estimate for the access method
is produced in best_access_path() by using actual_rec_per_key().
Make test_if_cheaper_ordering() also use actual_rec_per_key().
Also make several getter function "const" to make this compile.
Also adjusted the testcase to handle this (the change backported from
11.0)
This patch also fixes:
MDEV-33050 Build-in schemas like oracle_schema are accent insensitive
MDEV-33084 LASTVAL(t1) and LASTVAL(T1) do not work well with lower-case-table-names=0
MDEV-33085 Tables T1 and t1 do not work well with ENGINE=CSV and lower-case-table-names=0
MDEV-33086 SHOW OPEN TABLES IN DB1 -- is case insensitive with lower-case-table-names=0
MDEV-33088 Cannot create triggers in the database `MYSQL`
MDEV-33103 LOCK TABLE t1 AS t2 -- alias is not case sensitive with lower-case-table-names=0
MDEV-33109 DROP DATABASE MYSQL -- does not drop SP with lower-case-table-names=0
MDEV-33110 HANDLER commands are case insensitive with lower-case-table-names=0
MDEV-33119 User is case insensitive in INFORMATION_SCHEMA.VIEWS
MDEV-33120 System log table names are case insensitive with lower-cast-table-names=0
- Removing the virtual function strnncoll() from MY_COLLATION_HANDLER
- Adding a wrapper function CHARSET_INFO::streq(), to compare
two strings for equality. For now it calls strnncoll() internally.
In the future it will turn into a virtual function.
- Adding new accent sensitive case insensitive collations:
- utf8mb4_general1400_as_ci
- utf8mb3_general1400_as_ci
They implement accent sensitive case insensitive comparison.
The weight of a character is equal to the code point of its
upper case variant. These collations use Unicode-14.0.0 casefolding data.
The result of
my_charset_utf8mb3_general1400_as_ci.strcoll()
is very close to the former
my_charset_utf8mb3_general_ci.strcasecmp()
There is only a difference in a couple dozen rare characters, because:
- the switch from "tolower" to "toupper" comparison, to make
utf8mb3_general1400_as_ci closer to utf8mb3_general_ci
- the switch from Unicode-3.0.0 to Unicode-14.0.0
This difference should be tolarable. See the list of affected
characters in the MDEV description.
Note, utf8mb4_general1400_as_ci correctly handles non-BMP characters!
Unlike utf8mb4_general_ci, it does not treat all BMP characters
as equal.
- Adding classes representing names of the file based database objects:
Lex_ident_db
Lex_ident_table
Lex_ident_trigger
Their comparison collation depends on the underlying
file system case sensitivity and on --lower-case-table-names
and can be either my_charset_bin or my_charset_utf8mb3_general1400_as_ci.
- Adding classes representing names of other database objects,
whose names have case insensitive comparison style,
using my_charset_utf8mb3_general1400_as_ci:
Lex_ident_column
Lex_ident_sys_var
Lex_ident_user_var
Lex_ident_sp_var
Lex_ident_ps
Lex_ident_i_s_table
Lex_ident_window
Lex_ident_func
Lex_ident_partition
Lex_ident_with_element
Lex_ident_rpl_filter
Lex_ident_master_info
Lex_ident_host
Lex_ident_locale
Lex_ident_plugin
Lex_ident_engine
Lex_ident_server
Lex_ident_savepoint
Lex_ident_charset
engine_option_value::Name
- All the mentioned Lex_ident_xxx classes implement a method streq():
if (ident1.streq(ident2))
do_equal();
This method works as a wrapper for CHARSET_INFO::streq().
- Changing a lot of "LEX_CSTRING name" to "Lex_ident_xxx name"
in class members and in function/method parameters.
- Replacing all calls like
system_charset_info->coll->strcasecmp(ident1, ident2)
to
ident1.streq(ident2)
- Taking advantage of the c++11 user defined literal operator
for LEX_CSTRING (see m_strings.h) and Lex_ident_xxx (see lex_ident.h)
data types. Use example:
const Lex_ident_column primary_key_name= "PRIMARY"_Lex_ident_column;
is now a shorter version of:
const Lex_ident_column primary_key_name=
Lex_ident_column({STRING_WITH_LEN("PRIMARY")});
Other usage if persistent statistics is checking 'stats_is_read' in
caller, which is why this was not noticed earlier.
Other things:
- Simplified no_stat_values_provided
This was introduced in last merge with 10.6
The reason is that 10.6 does not need anything special to free histograms
as everything is allocated on a memroot.
In 10.10 histograms is using the vector class, which has some problems:
- No automatic free
- No memory usage accounting
(we should at some point remove vector usage because of the above problem)
Fixed by expliciting freeing histograms when freeing TABLE_STATISTICS
objects.
The MDEV-29693 conflict resolution is from Monty, as well as is
a bug fix where ANALYZE TABLE wrongly built histograms for
single-column PRIMARY KEY.
Also includes a fix for safe_malloc error reporting.
Other things:
- Copied main.log_slow from 10.4 to avoid mtr issue
Disabled test:
- spider/bugfix.mdev_27239 because we started to get
+Error 1429 Unable to connect to foreign data source: localhost
-Error 1158 Got an error reading communication packets
- main.delayed
- Bug#54332 Deadlock with two connections doing LOCK TABLE+INSERT DELAYED
This part is disabled for now as it fails randomly with different
warnings/errors (no corruption).
Example of what causes the problem:
T1: ANALYZE TABLE starts to collect statistics
T2: ALTER TABLE starts by deleting statistics for all changed fields,
then creates a temp table and copies data to it.
T1: ANALYZE ends and writes to the statistics tables.
T2: ALTER TABLE renames temp table in place of the old table.
Now the statistics from analyze matches the old deleted tables.
Fixed by waiting to delete old statistics until ALTER TABLE is
the only one using the old table and ensure that rename of columns
can handle swapping of column names.
rename_columns_in_stat_table() (former rename_column_in_stat_tables())
now takes a list of columns to rename. It uses the following algorithm
to update column_stats to be able to handle circular renames
- While there are columns to be renamed and it is the first loop or
last rename loop did change something.
- Loop over all columns to be renamed
- Change column name in column_stat
- If fail because of duplicate key
- If this is first change attempt for this column
- Change column name to a temporary column name
- If there was a conflicting row, replace it with the current row.
else
- Remove entry from column list
- Loop over all remaining columns in the list
- Remove the conflicting row
- Change column from temporary name to final name in column_stat
Other things:
- Don't flush tables for every operation. Only flush when all updates
are done.
- Rename of columns was not handled in case of ALGORITHM=copy (old bug).
- Fixed that we do not collect statistics for hidden hash columns
used by UNIQUE constraint on long values.
- Fixed that we do not collect statistics for blob columns referred by
generated virtual columns. This was achieved by storing the fields for
which we want to have statistics in table->has_value_set instead of
in table->read_set.
- Rename of indexes was not handled for persistent statistics.
- This is now handled similar as rename of columns. Renamed columns
are now stored in 'rename_stat_indexes' and handled in
Alter_info::delete_statistics() together with drooped indexes.
- ALTER TABLE .. ADD INDEX may instead of creating a new index rename
an existing generated foreign key index. This was not reflected in
the index_stats table because this was handled in
mysql_prepare_create_table instead instead of in the mysql_alter() code.
Fixed by adding a call in mysql_prepare_create_table() to drop the
changed index.
I also had to change the code that 'marked the index' to be ignored
with code that would not destroy the original index name.
Reviewer: Sergei Petrunia <sergey@mariadb.com>
This commits enables reloading of engine-independent statistics
without flushing the table from table definition cache.
This is achieved by allowing multiple version of the
TABLE_STATISTICS_CB object and having independent pointers to it in
TABLE and TABLE_SHARE. The TABLE_STATISTICS_CB object have reference
pointers and are freed when no one is pointing to it anymore.
TABLE's TABLE_STATISTICS_CB pointer is updated to use the
TABLE_SHARE's pointer when read_statistics_for_tables() is called at
the beginning of a query.
Main changes:
- read_statistics_for_table() will allocate an new TABLE_STATISTICS_CB
object.
- All get_stat_values() functions has a new parameter that tells
where collected data should be stored. get_stat_values() are not
using the table_field object anymore to store data.
- All get_stat_values() functions returns 1 if they found any
data in the statistics tables.
Other things:
- Fixed INSERT DELAYED to not read statistics tables.
- Removed Statistics_state from TABLE_STATISTICS_CB as this is not
needed anymore as wer are not changing TABLE_SHARE->stats_cb while
calculating or loading statistics.
- Store values used with store_from_statistical_minmax_field() in
TABLE_STATISTICS_CB::mem_root. This allowed me to remove the function
delete_stat_values_for_table_share().
- Field_blob::store_from_statistical_minmax_field() is implemented
but is not normally used as we do not yet support EIS statistics
for blobs. For example Field_blob::update_min() and
Field_blob::update_max() are not implemented.
Note that the function can be called if there is an concurrent
"ALTER TABLE MODIFY field BLOB" running because of a bug in
ALTER TABLE where it deletes entries from column_stats
before it has an exclusive lock on the table.
- Use result of field->val_str(&val) as a pointer to the result
instead of val (safetly fix).
- Allocate memory for collected statistics in THD::mem_root, not in
in TABLE::mem_root. This could cause the TABLE object to grow if a
ANALYZE TABLE was run many times on the same table.
This was done in allocate_statistics_for_table(),
create_min_max_statistical_fields_for_table() and
create_min_max_statistical_fields_for_table_share().
- Store in TABLE_STATISTICS_CB::stats_available which statistics was
found in the statistics tables.
- Removed index_table from class Index_prefix_calc as it was not used.
- Added TABLE_SHARE::LOCK_statistics to ensure we don't load EITS
in parallel. First thread will load it, others will reuse the
loaded data.
- Eliminate read_histograms_for_table(). The loading happens within
read_statistics_for_tables() if histograms are needed.
One downside is that if we have read statistics without histograms
before and someone requires histograms, we have to read all statistics
again (once) from the statistics tables.
A smaller downside is the need to call alloc_root() for each
individual histogram. Before we could allocate all the space for
histograms with a single alloc_root.
- Fixed bug in MyISAM and Aria where they did not properly notice
that table had changed after analyze table. This was not a problem
before this patch as then the MyISAM and Aria tables where flushed
as part of ANALYZE table which did hide this issue.
- Fixed a bug in ANALYZE table where table->records could be seen as 0
in collect_statistics_for_table(). The effect of this unlikely bug
was that a full table scan could be done even if
analyze_sample_percentage was not set to 1.
- Changed multiple mallocs in a row to use multi_alloc_root().
- Added a mutex protection in update_statistics_for_table() to ensure
that several tables are not updating the statistics at the same time.
Some of the changes in sql_statistics.cc are based on a patch from
Oleg Smirnov <olernov@gmail.com>
Co-authored-by: Oleg Smirnov <olernov@gmail.com>
Co-authored-by: Vicentiu Ciorbaru <cvicentiu@gmail.com>
Reviewer: Sergei Petrunia <sergey@mariadb.com>
- agressively -> aggressively
- exising -> existing
- occured -> occurred
- releated -> related
- seperated -> separated
- sucess -> success
- use use -> use
All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.
Followup: remove this line from get_column_range_cardinality()
set_if_bigger(res, col_stats->get_avg_frequency());
and make sure it is only used with the binary histograms.
For JSON histograms, it makes the estimates unnecessarily imprecise.
Previous JSON parser was using an API which made the parsing
inefficient: the same JSON contents was parsed again and again.
Switch to using a lower-level parsing API which allows to do
parsing in an efficient way.
Factor the code that updates count, count_distinct,
count_distinct_single_occurrence into class Basic_stats_collector
Change from Histogram_builder and its descendant Histogram_builder_json
to Histogram_builder (the interface), and Histogram_binary_builder,
Histogram_json_builder.
In Histogram_json_builder, do not forget to collect the right bound
of the right-most bucket.
* it also adds an "explain select" statement to the test so that the fprintf calls
can print the computed intervals to mysqld.1.err
Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
This fixes the wrong calculation for avg_frequency in json histograms
by replacing the specific histogram objects with the generic Histogram_base class.
It also restores get/set size functions as they were useful in calculating fields
for binary histogram.
Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
A demo of how to use in-memory data structure for histogram.
The patch shows how to
* convert string form of data to binary form
* compare two values in binary form
* compute a fraction for val in [X, Y] range.
grep for GSOC-TODO for notes.
Preparation for handling different kinds of histograms:
- In Column_statistics, change "Histogram histogram" into
"Histogram *histogram_". This allows for different kinds
of Histogram classes with virtual functions.
- [Almost] remove the usage of Histogram->set_values and
Histogram->set_size. The code outside the histogram should
not make any assumptions about what/how is stored in the Histogram.
- Introduce drafts of methods to read/save histograms to/from disk.
This fixes the memory allocation for json histogram builder and add more column types for testing.
Some challenges at the moment include:
* Garbage value at the end of JSON array still persists.
* Garbage value also gets appended to bucket values if the column is a primary key.
* There's a memory leak resulting in a "Warning: Memory not freed" message at the end of tests.
Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
The issue here was histogram statistics were being used even when
the level of optimizer_use_condition_selectivity doesn't allow
usage of statistics from histogram.
The histogram statistics are read for a table only when
optimizer_use_condition_selectivity > 3. But the TABLE structure can be
stored in the internal table cache and be reused for the next query.
So in this case the histogram statistics will be available for the next query.
The fix would be to make sure to use the histogram statistics only when
optimizer_use_condition_selectivity > 3.
