we had the statistics tables in the FROM list of the select.
The statistics for tables are not read in such cases, so we need
to check this case separately.
To read histograms for a table, we should check if the allocation of statistics was done or not,
if not done we should not try to read histograms for such a table.
The command SHOW INDEXES ignored setting of the system variable
use_stat_tables to the value of 'preferably' and and showed statistical
data received from the engine. Similarly queries over the table
STATISTICS from INFORMATION_SCHEMA ignored this setting. It happened
because the function fill_schema_table_by_open() did not read any data
from statistical tables.
for the small InnoDB table
This bug was introduced by the patch 6c414fcf89.
The patch has not taken into account that some objects of the Field_* types
are created only for TABLE_SHARE and the field 'table' is set to NULL
for them. In particular such are objects created to store statistical
min/max values for columns.
for blob column
ANALYZE TABLE <table> does not collect statistical data on min/max values
for BLOB columns of <table>. However these values can be added into
mysql.column_stats manually by executing proper statements.
Unfortunately this led to a memory leak because the memory allocated
for these values was never freed.
This patch provides the server with a function to free memory allocated
for min/max statistical values of BLOB types.
Temporarily changed the test case until MDEV-16711 is fixed as without
this fix the test case for MDEV-16757 did not fail only for 10.0.
for blob column
ANALYZE TABLE <table> does not collect statistical data on min/max values
for BLOB columns of <table>. However these values can be added into
mysql.column_stats manually by executing proper statements.
Unfortunately this led to a memory leak because the memory allocated
for these values was never freed.
This patch provides the server with a function to free memory allocated
for min/max statistical values of BLOB types.
Backport the fix f214d36512 to 10.0
Author: Sergei Golubchik <serg@mariadb.org>
Date: Tue Apr 17 00:44:34 2018 +0200
ASAN error in is_stat_table()
don't memcmp beyond the first argument's end
Also: use my_strcasecmp(table_alias_charset), like elsewhere, not memcmp
RENAME TABLE code tries to update EITS statistics. It hung, because
it used an index on (db_name,table_name) to find the table, and attempted
to update these values at the same time. The fix is do what SQL UPDATE
statement does when updating index that it's used for scanning:
- First, buffer the rowids of rows to be updated,
- then make the second pass to actually update the rows
Also fixed the call to rename_table_in_stat_tables() in sql_rename.cc
to pass the correct new database (before, it passed old db_name so cross-
database renames were not handled correctly).
Variant #2, with review feedback addressed.
table_stat -> table_stats
column_stat -> column_stats
index_stat -> index_stats
to be in line with the names of innodb statistical tables
from mysql-5.6: innodb_table_stats and innodb_index_stats.
The function collect_statistics_for_table() when scanning a table
did not take into account that the handler function ha_rnd_next
could return the code HA_ERR_RECORD_DELETE that should not be
considered as an indication of an error.
Also fixed a potential memory leak in this function.
With the new code of mysql-5.5 for metadata locking the function
unlock_tables_n_open_system_tables_for_write should not explicitly
unlock tables for which external locks have been set and should not
explicitly reset thd->lock to 0.
- Moved the definitions of the classes to store data from persistent
statistical tables into statistics.h, leaving in other internal
data structures only references to the corresponding objects.
- Defined class Column_statistics_collected derived from the class
Column_statistics. This is a helper class to collect statistics
on columns.
- Moved references to read statistics to TABLE SHARE, leaving the
the reference to the collected statistics in TABLE.
- Added a new clone method for the class Field allowing to clone
fields attached to table shares. It was was used to create
fields for min/max values in the memory of the table share.
A lso:
- Added procedures to allocate memory for statistical data in
the table share memory and in table memory.
Also:
- Added a test case demonstrating how ANALYZE could work in parallel
to collect statistics on different indexes of the same table.
- Added a test two demonstrate how two connections working
simultaneously could allocate memory for statistical data in the
table share memory.
mysql.column_stat, mysql.table_stat for the type DECIMAL(12,4).
When cached the values from these columns are multiplied by factor 10^5
and stored as ulong numbers now.
Renamed the system variable optimizer_use_stat_tables to use_stat_tables.
This variable now has only 3 possible values:
'never', 'complementary', 'preferably'.
If the server has been launched with
--use-stat-tables='complementary'|'preferably'
then the statictics tables can be employed by the optimizer and by the
ANALYZE command.
