MySQL: 執(zhí)行計劃中filtered的計算方式和影響

filtered主要的功能是說明撕氧，引擎層掃描數(shù)據(jù)后根據(jù)額外的where條件過濾后剩下值的一個百分比瘤缩，因為遇到一個問題和其相關(guān)，不由得想看看其估算過程伦泥，主要考慮如下

主要代碼5.7.22
主要考慮等值過濾條件
8.0.28帶直方圖測試

一款咖、計算方式

經(jīng)過debug發(fā)現(xiàn)其實filter的計算還是比較簡單的何暮，其主要函數(shù)為calculate_condition_filter

其中定義了幾個宏
/// Filtering effect for equalities: col1 = col2
#define COND_FILTER_EQUALITY 0.1f
/// Filtering effect for inequalities: col1 > col2
#define COND_FILTER_INEQUALITY 0.3333f
/// Filtering effect for between: col1 BETWEEN a AND b
#define COND_FILTER_BETWEEN 0.1111f

對于等值來講我們用到的就是COND_FILTER_EQUALITY宏，其固定為10%铐殃，下列的估算方式這個宏會參與計算。主要的計算流程為：

1. 每個不能使用索引的where條件計算為 max(1/n_rows,0.1)

這個部分來自Item_func_eq::get_filtering_effect跨新，這里的Item_func_eq就是每個where等值條件富腊，可以清晰看到

  return fld->get_cond_filter_default_probability(rows_in_table,
                                                  COND_FILTER_EQUALITY);//0.1f
                                                  
Item_field::get_cond_filter_default_probability

return std::max(static_cast<float>(1/max_distinct_values), default_filter);

2. 關(guān)于n_rows到底是什么?

那么這里有一個主要的問題，就是這個n_rows 行數(shù)到底代表的是什么域帐，首先在函數(shù)calculate_condition_filter中可以看到赘被，如下代碼

    filtered*=
      tab->join()->where_cond->get_filtering_effect(tab->table_ref->map(),
                                                    used_tables,
                                                    &table->tmp_set,
                                          static_cast<double>(tab->records()));

而這里的where_cond就是我們where條件后面用不到索引的那些條件，其中行數(shù)比較關(guān)鍵為tab->records()肖揣，如果簡單看一下實際上這個值為

QEP_shared中的(執(zhí)行計劃相關(guān))
  /**
     Either #rows in the table or 1 for const table.
     Used in optimization, and also in execution for FOUND_ROWS().
  */
  ha_rows   m_records;

其設(shè)置為 QEP_shared::set_records民假，

image.png

最終可以看到這個值實際上來自

tab->set_records(tab->found_records= tab->table()->file->stats.records);
其中tab->table()返回對象為TABLE結(jié)構(gòu)體，也就是我們常說的table_cache

它就是innodb底層的統(tǒng)計數(shù)據(jù)龙优，代表是表中預(yù)估的行數(shù)羊异，可在函數(shù)ha_innobase::info_low中找到如下：

n_rows = ib_table->stat_n_rows;
....
stats.records = (ha_rows) n_rows;

簡單說就是mysql.innodb_table_stats/information_schema.tables下那個表數(shù)據(jù)的行數(shù)。

3. 如果有多個條件則通過各自filter相乘的方式進(jìn)行計算彤断，得到最終值

這部分來自Item_cond_and::get_filtering_effect野舶，and 也是一個item，其下面包含2個time宰衙，代碼和注釋說明了一切

  /*
    Calculated as "Conjunction of independent events":
       P(A and B ...) = P(A) * P(B) * ...
  */
  while ((item= it++))
    filtered*= item->get_filtering_effect(filter_for_table,
                                        read_tables,
                                        fields_to_ignore,
                                        rows_in_table);
  return filtered;

這個就不需要過多解釋了吧平道。

4. 如果最終計算的filter和1/num_rows之間判斷，取max(1/n_rows,0.1)

注意這里和前面不同供炼，第1點是每個where條件的filter不同一屋，這里是最終計算的filter

filtered 在 calculate_condition_filter 中進(jìn)行計算，如下

filtered= max(filtered, 1.0f / tab->records());

5. 如果預(yù)估掃描的行數(shù)*計算的最終filter 小于 0.05則取0.05

注意這里和前面不同袋哼，第1點是每個where條件的filter不同冀墨，這里是最終計算的filtered 在 calculate_condition_filter 中進(jìn)行計算，如下

  if ((filtered * fanout) < 0.05f)  //扇出
    filtered= 0.05f/static_cast<float>(fanout);

總的來說先嬉，filtered幾乎是一個預(yù)估的計算轧苫，可以作為參考但是一般不會太準(zhǔn)，其參與計算的元素主要包含：

0.1 固定寫死值
0.05 固定寫死的值
1/num_rows 也沒有過多的考慮偏移量的問題疫蔓，其中num_rows 為表的總行數(shù)
預(yù)估引擎層掃描的行數(shù)

這就可能導(dǎo)致執(zhí)行計劃中join 之類的選擇錯驅(qū)動表含懊，因為這種算法的過濾性完全是估算的，沒有基數(shù)等統(tǒng)計數(shù)據(jù)作為標(biāo)準(zhǔn)（或者索引下探動態(tài)統(tǒng)計dive ）衅胀，當(dāng)然到了8.0可以考慮直方圖岔乔，最后我們來進(jìn)行簡單測試。下面來測試一下滚躯，看看是不是這樣計算的雏门。

二嘿歌、測試

先建立2個表如下：

mysql> create table testfil(a int,b int,c int);
Query OK, 0 rows affected (0.01 sec)

mysql> insert into testfil values(1,1,1);
Query OK, 1 row affected (0.00 sec)

mysql> insert into testfil values(2,2,2);
Query OK, 1 row affected (0.01 sec)

mysql> insert into testfil values(3,3,3);
Query OK, 1 row affected (0.01 sec)

mysql> insert into testfil values(4,4,4);
Query OK, 1 row affected (0.00 sec)

mysql> insert into testfil values(4,4,4);
Query OK, 1 row affected (0.00 sec)

mysql> insert into testfil values(4,4,4);
Query OK, 1 row affected (0.00 sec)

mysql> insert into testfil values(4,4,4);
Query OK, 1 row affected (0.01 sec)

mysql> insert into testfil values(3,3,3);
Query OK, 1 row affected (0.00 sec)

mysql> select * from testfil;
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    1 |    1 |    1 |
|    2 |    2 |    2 |
|    4 |    4 |    4 |
|    4 |    4 |    4 |
|    4 |    4 |    4 |
|    4 |    4 |    4 |
|    3 |    3 |    3 |
+------+------+------+
7 rows in set (0.00 sec)

mysql> alter table testfil add key(a);
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> create table testfil2 like testfil;
Query OK, 0 rows affected (0.01 sec)

mysql> insert into testfil2 select * from testfil;
Query OK, 7 rows affected (0.01 sec)
Records: 7  Duplicates: 0  Warnings: 0
...
mysql> insert into testfil2 select * from testfil2;
Query OK, 14336 rows affected (4.91 sec)
Records: 14336  Duplicates: 0  Warnings: 0

mysql> select table_name,n_rows from mysql.innodb_table_stats where table_name in ('testfil','testfil2');
+------------+--------+
| table_name | n_rows |
+------------+--------+
| testfil    |      7 |
| testfil2   |  28755 |
+------------+--------+
2 rows in set (0.09 sec)

mysql> select table_name,TABLE_ROWS from information_schema.tables  where table_name in ('testfil','testfil2');
+------------+------------+
| table_name | TABLE_ROWS |
+------------+------------+
| testfil    |          7 |
| testfil2   |      28755 |
+------------+------------+
2 rows in set (0.13 sec)

這里主要是建立2個表1個小表1個大表，我們分別來看茁影。

測試單個where條件宙帝，小表

mysql> desc select * from testfil where b=1 ;
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | testfil | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    7 |    14.29 | Using where |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.01 sec)

mysql> desc select * from testfil where b=4 ;
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | testfil | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    7 |    14.29 | Using where |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

這里我們明顯的看到，雖然等于4的行是比較多的募闲，等于1的行只有1行步脓，但是他們計算的filtered都是1/7左右，又因為1/7 > 0.1 因此顯示為14.29%浩螺，很明顯沒有考慮數(shù)據(jù)的傾斜度

測試單個where條件靴患，大表

mysql> desc select * from testfil2 where b=1 ;
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
| id | select_type | table    | partitions | type | possible_keys | key  | key_len | ref  | rows  | filtered | Extra       |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
|  1 | SIMPLE      | testfil2 | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 28755 |    10.00 | Using where |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

mysql> desc select * from testfil2 where b=4 ;
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
| id | select_type | table    | partitions | type | possible_keys | key  | key_len | ref  | rows  | filtered | Extra       |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
|  1 | SIMPLE      | testfil2 | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 28755 |    10.00 | Using where |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

這里也顯然，1/28755< 0.1要出，因此都顯示10%鸳君，不管數(shù)據(jù)偏移量。

測試兩個個where條件患蹂，小表

mysql> desc select * from testfil where b=1 and c=1;
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | testfil | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    7 |    14.29 | Using where |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.01 sec)

mysql> desc select * from testfil where b=4 and c=4;
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | testfil | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    7 |    14.29 | Using where |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

這里依舊顯示14.29%或颊，因為filter初始化計算出來為(1/7)*(1/7),根據(jù)第4點小于1/7,依舊算1/7，也就是14.29%

DEBUG如下

1416      filtered= max(filtered, 1.0f / tab->records());
(gdb) p filtered
$1 = 0.0204081647 ((1/7)*(1/7))
(gdb) n
1428      if ((filtered * fanout) < 0.05f)
(gdb) p filtered
$2 = 0.142857149

依舊不考慮數(shù)據(jù)切斜度况脆。

測試兩個where條件饭宾，大表

mysql> desc select * from testfil2 where b=1 and c=1;
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
| id | select_type | table    | partitions | type | possible_keys | key  | key_len | ref  | rows  | filtered | Extra       |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
|  1 | SIMPLE      | testfil2 | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 28755 |     1.00 | Using where |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
1 row in set, 1 warning (0.01 sec)

mysql> desc select * from testfil2 where b=4 and c=4;
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
| id | select_type | table    | partitions | type | possible_keys | key  | key_len | ref  | rows  | filtered | Extra       |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
|  1 | SIMPLE      | testfil2 | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 28755 |     1.00 | Using where |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

這里很顯然就是兩個0.1相乘，0.1*0.1=0.01 也就是1%格了，而0.01 > 1/28755 看铆，因此直接顯示

測試帶索引定位數(shù)據(jù)掃描和兩個where條件

這種情況主要是要測試最后一點就是第5點的0.05測試出來，建立的表如下：

mysql> show create table testauto \G
*************************** 1. row ***************************
       Table: testauto
Create Table: CREATE TABLE `testauto` (
  `a` int(11) NOT NULL,
  `b` int(11) DEFAULT NULL,
  `c` int(11) DEFAULT NULL,
  KEY `a` (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)

mysql> select count(*) from testauto;
+----------+
| count(*) |
+----------+
|    16384 |
+----------+
1 row in set (0.77 sec)

mysql> select table_name,n_rows from mysql.innodb_table_stats where table_name in ('testauto');
+------------+--------+
| table_name | n_rows |
+------------+--------+
| testauto   |  16188 |
+------------+--------+
1 row in set (0.10 sec)

這里字段a有索引盛末，且里面的數(shù)字是唯一值弹惦，那么如下語句

mysql> desc select * from testauto where a=100 and b=1 and c=1;
+----+-------------+----------+------------+------+---------------+------+---------+-------+------+----------+-------------+
| id | select_type | table    | partitions | type | possible_keys | key  | key_len | ref   | rows | filtered | Extra       |
+----+-------------+----------+------------+------+---------------+------+---------+-------+------+----------+-------------+
|  1 | SIMPLE      | testauto | NULL       | ref  | a             | a    | 4       | const |    1 |     5.00 | Using where |
+----+-------------+----------+------------+------+---------------+------+---------+-------+------+----------+-------------+
1 row in set, 1 warning (0.01 sec)

我們看到filtered為5%，也就是第5點生效悄但，因為 rows=1棠隐，計算出來的filter應(yīng)該為0.01，而1*0.01< 0.05 所以直接置為0.05檐嚣，也就是5%助泽。看下DEBUG

1416      filtered= max(filtered, 1.0f / tab->records());
(gdb) 
1428      if ((filtered * fanout) < 0.05f)
(gdb) p filtered
$3 = 0.0100000007
(gdb) p fanout
$4 = 1
(gdb) n
1429        filtered= 0.05f/static_cast<float>(fanout);
(gdb) n
1433      bitmap_clear_all(&table->tmp_set);
(gdb) p filtered
$5 = 0.0500000007

join測試

mysql> desc select * from testauto a,testfil2 b  where a.a=b.a and a.b=1 and a.c=1;
+----+-------------+-------+------------+------+---------------+------+---------+--------+-------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key  | key_len | ref    | rows  | filtered | Extra       |
+----+-------------+-------+------------+------+---------------+------+---------+--------+-------+----------+-------------+
|  1 | SIMPLE      | a     | NULL       | ALL  | a             | NULL | NULL    | NULL   | 16188 |     1.00 | Using where |
|  1 | SIMPLE      | b     | NULL       | ref  | a             | a    | 5       | tp.a.a |     1 |   100.00 | NULL        |
+----+-------------+-------+------------+------+---------------+------+---------+--------+-------+----------+-------------+
2 rows in set, 1 warning (0.00 sec)

mysql> desc select * from testauto a,testfil2 b  where a.a=b.a and a.b=1 and a.c=1 and a.a=1;
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key  | key_len | ref   | rows | filtered | Extra       |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
|  1 | SIMPLE      | a     | NULL       | ref  | a             | a    | 4       | const |    1 |     5.00 | Using where |
|  1 | SIMPLE      | b     | NULL       | ref  | a             | a    | 5       | const | 4096 |   100.00 | NULL        |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
2 rows in set, 1 warning (0.00 sec)

mysql> desc select * from testauto a,testfil2 b  where a.a=b.a and a.b=1 and a.c=1 and a.a=1 and b.c=1;
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key  | key_len | ref   | rows | filtered | Extra       |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
|  1 | SIMPLE      | a     | NULL       | ref  | a             | a    | 4       | const |    1 |     5.00 | Using where |
|  1 | SIMPLE      | b     | NULL       | ref  | a             | a    | 5       | const | 4096 |    10.00 | Using where |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
2 rows in set, 1 warning (0.01 sec)

mysql> desc select * from testauto a,testfil2 b  where a.a=b.a and a.b=1 and a.c=1 and a.a=1 and b.c=1 and b.b=1;
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key  | key_len | ref   | rows | filtered | Extra       |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
|  1 | SIMPLE      | a     | NULL       | ref  | a             | a    | 4       | const |    1 |     5.00 | Using where |
|  1 | SIMPLE      | b     | NULL       | ref  | a             | a    | 5       | const | 4096 |     1.00 | Using where |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+

這里過多分析了嚎京，實際上join中依舊生效嗡贺，只是a.a=b.a關(guān)聯(lián)條件要作為被驅(qū)動表的一個where條件來考慮。

三鞍帝、8.0 簡單測試（8.0.28）

依舊使用上面的表诫睬，進(jìn)行測試

不帶直方圖

mysql> desc select * from testfil where b=4  and c=4;
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | testfil | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    7 |    14.29 | Using where |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

mysql> desc select * from testfil2 where b=4  and c=4;
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
| id | select_type | table    | partitions | type | possible_keys | key  | key_len | ref  | rows  | filtered | Extra       |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
|  1 | SIMPLE      | testfil2 | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 86265 |     1.00 | Using where |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

依舊不考慮數(shù)據(jù)的傾斜度。

收集直方圖后執(zhí)行

我這里不同的數(shù)據(jù)很少帕涌，使用等寬直方圖就可以了摄凡，如下：


mysql> ANALYZE TABLE testfil UPDATE HISTOGRAM ON b,c WITH 10 BUCKETS;
+----------------+-----------+----------+----------------------------------------------+
| Table          | Op        | Msg_type | Msg_text                                     |
+----------------+-----------+----------+----------------------------------------------+
| mytest.testfil | histogram | status   | Histogram statistics created for column 'b'. |
| mytest.testfil | histogram | status   | Histogram statistics created for column 'c'. |
+----------------+-----------+----------+----------------------------------------------+
2 rows in set (0.04 sec)

mysql> ANALYZE TABLE testfil2 UPDATE HISTOGRAM ON b,c WITH 10 BUCKETS;
+-----------------+-----------+----------+----------------------------------------------+
| Table           | Op        | Msg_type | Msg_text                                     |
+-----------------+-----------+----------+----------------------------------------------+
| mytest.testfil2 | histogram | status   | Histogram statistics created for column 'b'. |
| mytest.testfil2 | histogram | status   | Histogram statistics created for column 'c'. |
+-----------------+-----------+----------+----------------------------------------------+
2 rows in set (5.21 sec)

mysql> desc select * from testfil where b=4  and c=4;
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table   | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | testfil | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    7 |    32.65 | Using where |
+----+-------------+---------+------------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

mysql> desc select * from testfil2 where b=4  and c=4;
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
| id | select_type | table    | partitions | type | possible_keys | key  | key_len | ref  | rows  | filtered | Extra       |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
|  1 | SIMPLE      | testfil2 | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 86265 |    32.65 | Using where |
+----+-------------+----------+------------+------+---------------+------+---------+------+-------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

mysql>

我們可以看到直方圖確實影響了filtered的計算续徽，也更加準(zhǔn)確了，但是8.0的直方圖默認(rèn)沒有收集亲澡，因此使用不多钦扭，我的了解也比較有限。如果不使用直方圖filter還是5.7的計算方式床绪。

附錄：使用的BUG點

1       breakpoint     keep y   0x0000000000eb13ac in main(int, char**) at /opt/percona-server-locks-detail-5.7.22/sql/main.cc:25
        breakpoint already hit 1 time
2       breakpoint     keep y   0x0000000001727699 in Explain_join::explain_rows_and_filtered() at /opt/percona-server-locks-detail-5.7.22/sql/opt_explain.cc:1480
        breakpoint already hit 14 times
3       breakpoint     keep y   0x0000000001589411 in calculate_condition_filter(JOIN_TAB const*, Key_use const*, unsigned long long, double, bool) 
                                                   at /opt/percona-server-locks-detail-5.7.22/sql/sql_planner.cc:1219
        breakpoint already hit 26 times
5       breakpoint     keep y   0x0000000000fadb41 in Item_equal::get_filtering_effect(unsigned long long, unsigned long long, st_bitmap const*, double) 
                                                   at /opt/percona-server-locks-detail-5.7.22/sql/item_cmpfunc.cc:7478
        breakpoint already hit 4 times
6       breakpoint     keep y   0x0000000000f83dc2 in Item_field::get_cond_filter_default_probability(double, float) const at /opt/percona-server-locks-detail-5.7.22/sql/item.cc:7905
        breakpoint already hit 3 times

最后編輯于：2022.11.26 11:27:11

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