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MDEV-34993, part2: backport optimizer_adjust_secondary_key_costs

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...and make the fix for MDEV-34993 switchable. It is enabled by default
and controlled with @optimizer_adjust_secondary_key_costs=fix_card_multiplier
This commit is contained in:
Sergei Petrunia 2024-09-24 10:23:34 +03:00
parent 8166a5d33d
commit 1cda4726ca
9 changed files with 175 additions and 1 deletions
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7
mysql-test/main/mysqld--help.result
View file

@ -682,6 +682,12 @@ The following specify which files/extra groups are read (specified before remain
max_connections*5 or max_connections + table_cache*2
(whichever is larger) number of file descriptors
(Automatically configured unless set explicitly)
--optimizer-adjust-secondary-key-costs=name
A bit field with the following values:
fix_card_multiplier = Fix the computation in
selectivity_for_indexes. selectivity_multiplier. This
variable will be deleted in MariaDB 11.0 as it is not
needed with the new 11.0 optimizer.
--optimizer-max-sel-arg-weight=#
The maximum weight of the SEL_ARG graph. Set to 0 for no
limit
@ -1642,6 +1648,7 @@ old-alter-table DEFAULT
old-mode
old-passwords FALSE
old-style-user-limits FALSE
optimizer-adjust-secondary-key-costs fix_card_multiplier
optimizer-max-sel-arg-weight 32000
optimizer-prune-level 1
optimizer-search-depth 62

54
mysql-test/main/selectivity_innodb_notembedded.result
View file

@ -280,7 +280,61 @@ JS
}
}
]
# Disable the fix and try the same:
set @@optimizer_adjust_secondary_key_costs='';
explain select * from t1
where
pk in (1,2,3,4,5) and
key1 <= 4;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY,key1 PRIMARY 4 NULL 5 Using where
drop table t1;
# Shows a high multiplier, without a "note":
select
json_detailed(json_extract(trace,'$**.selectivity_for_indexes')) as JS
from
information_schema.optimizer_trace;
JS
[
[
{
"index_name": "PRIMARY",
"selectivity_from_index": 0.005
},
{
"index_name": "key1",
"selectivity_from_index": 0.399,
"selectivity_multiplier": 90.9091
}
]
]
# Includes 1.79...e308 as cost:
select
json_detailed(json_extract(trace,'$**.best_access_path')) as JS
from
information_schema.optimizer_trace;
JS
[
{
"considered_access_paths":
[
{
"access_type": "range",
"resulting_rows": 181.3636545,
"cost": 1.79769e308,
"chosen": true
}
],
"chosen_access_method":
{
"type": "range",
"records": 181.3636545,
"cost": 1.79769e308,
"uses_join_buffering": false
}
}
]
set optimizer_adjust_secondary_key_costs=default;
#
# Clean up
#

54
mysql-test/main/selectivity_notembedded.result
View file

@ -275,7 +275,61 @@ JS
}
}
]
# Disable the fix and try the same:
set @@optimizer_adjust_secondary_key_costs='';
explain select * from t1
where
pk in (1,2,3,4,5) and
key1 <= 4;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY,key1 PRIMARY 4 NULL 5 Using index condition; Using where
drop table t1;
# Shows a high multiplier, without a "note":
select
json_detailed(json_extract(trace,'$**.selectivity_for_indexes')) as JS
from
information_schema.optimizer_trace;
JS
[
[
{
"index_name": "PRIMARY",
"selectivity_from_index": 0.005
},
{
"index_name": "key1",
"selectivity_from_index": 0.391,
"selectivity_multiplier": 90.9091
}
]
]
# Includes 1.79...e308 as cost:
select
json_detailed(json_extract(trace,'$**.best_access_path')) as JS
from
information_schema.optimizer_trace;
JS
[
{
"considered_access_paths":
[
{
"access_type": "range",
"resulting_rows": 177.7272905,
"cost": 1.79769e308,
"chosen": true
}
],
"chosen_access_method":
{
"type": "range",
"records": 177.7272905,
"cost": 1.79769e308,
"uses_join_buffering": false
}
}
]
set optimizer_adjust_secondary_key_costs=default;
#
# Clean up
#

18
mysql-test/main/selectivity_notembedded.test
View file

@ -257,7 +257,25 @@ select
from
information_schema.optimizer_trace;
--echo # Disable the fix and try the same:
set @@optimizer_adjust_secondary_key_costs='';
explain select * from t1
where
pk in (1,2,3,4,5) and
key1 <= 4;
drop table t1;
--echo # Shows a high multiplier, without a "note":
select
json_detailed(json_extract(trace,'$**.selectivity_for_indexes')) as JS
from
information_schema.optimizer_trace;
--echo # Includes 1.79...e308 as cost:
select
json_detailed(json_extract(trace,'$**.best_access_path')) as JS
from
information_schema.optimizer_trace;
set optimizer_adjust_secondary_key_costs=default;
--echo #
--echo # Clean up

10
mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
View file

@ -2402,6 +2402,16 @@ NUMERIC_BLOCK_SIZE 1
ENUM_VALUE_LIST NULL
READ_ONLY YES
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME OPTIMIZER_ADJUST_SECONDARY_KEY_COSTS
VARIABLE_SCOPE SESSION
VARIABLE_TYPE SET
VARIABLE_COMMENT A bit field with the following values: fix_card_multiplier = Fix the computation in selectivity_for_indexes. selectivity_multiplier. This variable will be deleted in MariaDB 11.0 as it is not needed with the new 11.0 optimizer.
NUMERIC_MIN_VALUE NULL
NUMERIC_MAX_VALUE NULL
NUMERIC_BLOCK_SIZE NULL
ENUM_VALUE_LIST fix_card_multiplier
READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME OPTIMIZER_MAX_SEL_ARG_WEIGHT
VARIABLE_SCOPE SESSION
VARIABLE_TYPE BIGINT UNSIGNED

4
sql/opt_range.cc
View file

@ -3521,7 +3521,9 @@ bool calculate_cond_selectivity_for_table(THD *thd, TABLE *table, Item **cond)
multiplied by quick_cond_selectivity above, so we will only
multiply it with selectivity_mult).
*/
if (selectivity_mult > 1.0 / quick_cond_selectivity)
if ((thd->variables.optimizer_adjust_secondary_key_costs &
OPTIMIZER_ADJ_FIX_CARD_MULT) &&
selectivity_mult > 1.0 / quick_cond_selectivity)
{
selectivity_for_index.add("note", "multiplier too high, clipping");
selectivity_mult= 1.0/quick_cond_selectivity;

5
sql/sql_class.h
View file

@ -672,6 +672,11 @@ typedef struct system_variables
ulonglong sortbuff_size;
ulonglong default_regex_flags;
ulonglong max_mem_used;
/*
A bitmap of OPTIMIZER_ADJ_* flags (defined in sql_priv.h).
See sys_vars.cc:adjust_secondary_key_cost for symbolic names.
*/
ulonglong optimizer_adjust_secondary_key_costs;
/**
Place holders to store Multi-source variables in sys_var.cc during

5
sql/sql_priv.h
View file

@ -266,6 +266,11 @@
OPTIMIZER_SWITCH_COND_PUSHDOWN_FROM_HAVING | \
OPTIMIZER_SWITCH_OPTIMIZE_JOIN_BUFFER_SIZE)
/*
See adjust_secondary_key_cost in sys_vars.cc for symbolic names.
*/
#define OPTIMIZER_ADJ_FIX_CARD_MULT (1)
/*
Replication uses 8 bytes to store SQL_MODE in the binary log. The day you
use strictly more than 64 bits by adding one more define above, you should

19
sql/sys_vars.cc
View file

@ -2777,6 +2777,25 @@ static Sys_var_ulong Sys_optimizer_trace_max_mem_size(
SESSION_VAR(optimizer_trace_max_mem_size), CMD_LINE(REQUIRED_ARG),
VALID_RANGE(0, ULONG_MAX), DEFAULT(1024 * 1024), BLOCK_SIZE(1));
/*
Symbolic names for OPTIMIZER_ADJ_* flags in sql_priv.h
*/
static const char *adjust_secondary_key_cost[]=
{
"fix_card_multiplier", 0
};
static Sys_var_set Sys_optimizer_adjust_secondary_key_costs(
"optimizer_adjust_secondary_key_costs",
"A bit field with the following values: "
"fix_card_multiplier = Fix the computation in selectivity_for_indexes."
" selectivity_multiplier. "
"This variable will be deleted in MariaDB 11.0 as it is not needed with the "
"new 11.0 optimizer.",
SESSION_VAR(optimizer_adjust_secondary_key_costs), CMD_LINE(REQUIRED_ARG),
adjust_secondary_key_cost, DEFAULT(OPTIMIZER_ADJ_FIX_CARD_MULT));
static Sys_var_charptr_fscs Sys_pid_file(
"pid_file", "Pid file used by safe_mysqld",
READ_ONLY GLOBAL_VAR(pidfile_name_ptr), CMD_LINE(REQUIRED_ARG),