介绍
本篇主要通过汇总网上的大牛的知识，简单介绍一下如何使用mysql的执行计划，并根据执行计划判断如何优化和是否索引最优。
执行计划可显示估计查询语句执行计划，从中可以分析查询的执行情况是否最优，有助于对不使用索引的语句进行优化。EXPLAIN对每个查询返回一行信息，列出了有序的表格，MySQL处理语句的时候读取他们。MySQL解决所有的连接使用嵌套连接方法。这意味读取第一张一行，然后匹配第二张表的所有行，第三张表甚至更多表。当所有的表在处理时，MySQL会输出已经查询出来的列，并且回溯到表继续查找直到所有的行被找到，从该表读取下一行，直到程序继续处理下一张表。 使用关键词 EXTENDED ，EXPLAIN 会处理通过 SHOW WARNINGS 看到的一些额外信息。EXPLAIN EXTENDED 会显示这些滤出的列。
语法：
代码语言：javascript复制EXPLAIN <select statement>; 输出表格字段如下：
代码语言：javascript复制 mysql> explain select * from mysql.user where user='root';
---- ------------- ------- ------ --------------- ------ --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ -------------
| 1 | SIMPLE | user | ALL | NULL | NULL | NULL | NULL | 4 | Using where |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------- Column | JSONName | Meaning |
|---|---|---|
id | select_id | 查询标识。id越大优先执行；id相同自上而下执行； |
select_type | None | 查询的类型 |
table | table_name | 查询的表 |
partitions | partitions | Thematching partitions |
type | access_type | 连接类型 |
possible_keys | possible_keys | 可能选择的索引 |
key | key | 实际使用的索引 |
key_len | key_length | 使用的索引长度 |
ref | ref | 哪一列或常数在查询中与索引键列一起使用 |
rows | rows | 估计查询的行数 |
filtered | filtered | 被条件过滤掉的行数百分比 |
Extra | None | 解决查询的一些额外信息 |
以下主要举例说明3个字段：select_type 、type、Extra
【select_type】
alue | JSONName | Meaning |
|---|---|---|
SIMPLE | None | 简单查询 (不使用UNION或子查询) |
PRIMARY | None | 外层查询，主查询 |
UNION | None | UNION中第二个语句或后面的语句 |
DEPENDENTUNION | dependent (true) | UNION中第二个语句或后面的语句,独立于外部查询 |
UNIONRESULT | union_result | UNION的结果 |
SUBQUERY | None | 子查询中第一个SELECT |
DEPENDENTSUBQUERY | dependent (true) | 子查询中第一个SELECT,独立于外部查询 |
DERIVED | None | 子查询在 FROM子句中 |
MATERIALIZED | materialized_from_subquery | 物化子查询（不清楚是什么样的查询语句？） |
UNCACHEABLESUBQUERY | cacheable (false) | 结果集不能被缓存的子查询，必须重新评估外层查询的每一行 |
UNCACHEABLEUNION | cacheable (false) | UNION中第二个语句或后面的语句属于不可缓存的子查询 |
创建测试表：
代码语言：javascript复制create table tabname (
id int auto_increment not null primary key,
name varchar(10) null,
indate datetime null,
tid int null,
key(tid),
key(indate)
)engine=innodb;
create table tabname2 (
id int auto_increment not null primary key,
name varchar(10) null,
indate datetime null,
tid int null,
key(tid),
key(indate)
)engine=myisam;
insert into tabname(name,indate,tid) values('love',now(),2),('lucky',now(),3),('passion',now(),4);
insert into tabname2(name,indate,tid) values('love',now(),2),('lucky',now(),3),('passion',now(),4); #SIMPLE
代码语言：javascript复制create table tabname (
id int auto_increment not null primary key,
name varchar(10) null,
indate datetime null,
tid int null,
key(tid),
key(indate)
)engine=innodb;
create table tabname2 (
id int auto_increment not null primary key,
name varchar(10) null,
indate datetime null,
tid int null,
key(tid),
key(indate)
)engine=myisam;
insert into tabname(name,indate,tid) values('love',now(),2),('lucky',now(),3),('passion',now(),4);
insert into tabname2(name,indate,tid) values('love',now(),2),('lucky',now(),3),('passion',now(),4); #PRIMARY / DERIVED
代码语言：javascript复制 mysql> explain select * from (select * from tabname) as a;
---- ------------- ------------ ------ --------------- ------ --------- ------ ------ -------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------------ ------ --------------- ------ --------- ------ ------ -------
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 3 | |
| 2 | DERIVED | tabname | ALL | NULL | NULL | NULL | NULL | 3 | |
---- ------------- ------------ ------ --------------- ------ --------- ------ ------ ------- #PRIMARY / UNION / UNION RESULT
代码语言：javascript复制 mysql> explain select * from tabname union select * from tabname;
mysql> explain select * from tabname union all select * from tabname;
---- -------------- ------------ ------ --------------- ------ --------- ------ ------ -------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- -------------- ------------ ------ --------------- ------ --------- ------ ------ -------
| 1 | PRIMARY | tabname | ALL | NULL | NULL | NULL | NULL | 3 | |
| 2 | UNION | tabname | ALL | NULL | NULL | NULL | NULL | 3 | |
| NULL | UNION RESULT | <union1,2> | ALL | NULL | NULL | NULL | NULL | NULL | |
---- -------------- ------------ ------ --------------- ------ --------- ------ ------ ------- mysql> explain select * from tabname where id=(select max(id) from tabname);
---- ------------- --------- ------- --------------- --------- --------- ------- ------ ------------------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------- --------------- --------- --------- ------- ------ ------------------------------
| 1 | PRIMARY | tabname | const | PRIMARY | PRIMARY | 4 | const | 1 | |
| 2 | SUBQUERY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Select tables optimized away |
---- ------------- --------- ------- --------------- --------- --------- ------- ------ ------------------------------ #PRIMARY / SUBQUERY
#PRIMARY / DEPENDENT SUBQUERY
[plain] view plain copy
代码语言：javascript复制 mysql> explain select * from tabname a where exists(select 1 from tabname b where a.id=b.id);
mysql> explain select *,(select name from tabname b where a.id=b.id) from tabname a;
mysql> explain select * from tabname where id not in(select id from tabname);
---- -------------------- --------- ----------------- --------------- --------- --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- -------------------- --------- ----------------- --------------- --------- --------- ------ ------ -------------
| 1 | PRIMARY | tabname | ALL | NULL | NULL | NULL | NULL | 3 | Using where |
| 2 | DEPENDENT SUBQUERY | tabname | unique_subquery | PRIMARY | PRIMARY | 4 | func | 1 | Using index |
---- -------------------- --------- ----------------- --------------- --------- --------- ------ ------ ------------- #PRIMARY / DEPENDENT UNION / DEPENDENT SUBQUERY / UNION RESULT
代码语言：javascript复制 mysql> explain select * from tabname where id in (select id from tabname union select id from tabname);
---- -------------------- ------------ -------- --------------- --------- --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- -------------------- ------------ -------- --------------- --------- --------- ------ ------ -------------
| 1 | PRIMARY | tabname | ALL | NULL | NULL | NULL | NULL | 3 | Using where |
| 2 | DEPENDENT SUBQUERY | tabname | eq_ref | PRIMARY | PRIMARY | 4 | func | 1 | Using index |
| 3 | DEPENDENT UNION | tabname | eq_ref | PRIMARY | PRIMARY | 4 | func | 1 | Using index |
| NULL| UNION RESULT | <union2,3> | ALL | NULL | NULL | NULL | NULL | NULL | |
---- -------------------- ------------ -------- --------------- --------- --------- ------ ------ ------------- 【type】
type | Meaning |
|---|---|
system | 表仅一行数据 (=system table).这是const连接类型的特例。 |
const | 表最多只有一个匹配行，在查询开始时被读取。因为只有一个值，优化器将该列值视为常量。当在primarykey或者unique索引作为常量比较时被使用。 |
eq_ref(engine=myisam) | 来自前面表的结果集中读取一行，这是除system和const外最好的连接类型。当在使用PRIMARYKEY或者UNIQUENOT NULL的索引时会被使用。 |
ref | 对于前面表的结果集匹配查询的所有行，当连接使用索引key时，或者索引不是PRIMARYKEY和UNIQUE，则使用该类型。如果使用索引匹配少量行时，是不错的连接类型。 |
ref_or_null | 连接类型类似ref，只是搜索的行中包含NULL值MySQL做了额外的查找。 |
fulltext | 使用全文索引时出现。 |
index_merge | 使用了索引合并优化。(未成功) |
unique_subquery | 该类型将ref替换成以下子查询的格式： valueIN (SELECTprimary_key FROMsingle_table WHERE some_expr) |
index_subquery | 与 unique_subquery类似，但是将主键改为非唯一索引： valueIN (SELECTkey_columnFROMsingle_table WHERE some_expr) |
range | 使用索引检索给定范围内的行。 |
index | 该连接类型与ALL相同，除了扫描索引树。如果查询的字段都在索引列中，则使用index类型，否则为ALL类型。 |
ALL | 对于前面表的结果集中，进行了全表扫描。最差的一种类型，应考虑查询优化了！ |
查询类型性能由优到差：
system > const > eq_ref > ref > fulltext > ref_or_null > index_merge > unique_subquery > index_subquery > range > index > ALL
#system
代码语言：javascript复制 mysql> explain select id from(select id from tabname where id=1) as a;
---- ------------- ------------ -------- --------------- --------- --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------------ -------- --------------- --------- --------- ------ ------ -------------
| 1 | PRIMARY | <derived2> | system | NULL | NULL | NULL | NULL | 1 | |
| 2 | DERIVED | tabname | const | PRIMARY | PRIMARY | 4 | | 1 | Using index |
---- ------------- ------------ -------- --------------- --------- --------- ------ ------ ------------- #const
代码语言：javascript复制 mysql> explain select * from tabname as a,tabname as b where a.id=b.id and a.id=1;
mysql> explain select * from tabname where id=1;
---- ------------- --------- ------- --------------- --------- --------- ------- ------ -------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------- --------------- --------- --------- ------- ------ -------
| 1 | SIMPLE | tabname | const | PRIMARY | PRIMARY | 4 | const | 1 | |
---- ------------- --------- ------- --------------- --------- --------- ------- ------ ------- #eq_ref(engine=myisam)
代码语言：javascript复制 mysql> explain select * from tabname2 as a,tabname2 as b where a.id=b.id;
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ -------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ -------
| 1 | SIMPLE | a | ALL | PRIMARY | NULL | NULL | NULL | 3 | |
| 1 | SIMPLE | b | eq_ref | PRIMARY | PRIMARY | 4 | test.a.id | 1 | |
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ ------- #ref
代码语言：javascript复制 mysql> explain select * from tabname as a,tabname as b where a.tid=b.tid and a.tid=2;
mysql> explain select * from tabname where tid=2;
---- ------------- --------- ------ --------------- ------ --------- ------- ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------ --------------- ------ --------- ------- ------ -------------
| 1 | SIMPLE | tabname | ref | tid | tid | 5 | const | 1 | Using where |
---- ------------- --------- ------ --------------- ------ --------- ------- ------ ------------- #ref_or_null
代码语言：javascript复制 mysql> explain select id,tid from tabname where tid=2 or tid is null;
---- ------------- --------- ------------- --------------- ------ --------- ------- ------ --------------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------------- --------------- ------ --------- ------- ------ --------------------------
| 1 | SIMPLE | tabname | ref_or_null | tid | tid | 5 | const | 2 | Using where; Using index |
---- ------------- --------- ------------- --------------- ------ --------- ------- ------ -------------------------- #fulltext
代码语言：javascript复制 mysql> explain select id,tid from tabname where tid=2 or tid is null;
---- ------------- --------- ------------- --------------- ------ --------- ------- ------ --------------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------------- --------------- ------ --------- ------- ------ --------------------------
| 1 | SIMPLE | tabname | ref_or_null | tid | tid | 5 | const | 2 | Using where; Using index |
---- ------------- --------- ------------- --------------- ------ --------- ------- ------ -------------------------- #index_merge(未成功)
代码语言：javascript复制mysql> explain select * from tabname where tid>1 or indate<now();
mysql> explain select * from tabname where (tid>1 or indate>now()) AND name<'kk'; #unique_subquery
代码语言：javascript复制 mysql> explain select * from tabname where tid in(select id from tabname);
mysql> explain select * from tabname where id in(select id from tabname);
---- -------------------- --------- ----------------- --------------- --------- --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- -------------------- --------- ----------------- --------------- --------- --------- ------ ------ -------------
| 1 | PRIMARY | tabname | ALL | NULL | NULL | NULL | NULL | 3 | Using where |
| 2 | DEPENDENT SUBQUERY | tabname | unique_subquery | PRIMARY | PRIMARY | 4 | func | 1 | Using index |
---- -------------------- --------- ----------------- --------------- --------- --------- ------ ------ ------------- #index_subquery
代码语言：javascript复制 mysql> explain select * from tabname where tid in(select tid from tabname);
mysql> explain select * from tabname where id in(select tid from tabname);
---- -------------------- --------- ---------------- --------------- ------ --------- ------ ------ --------------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- -------------------- --------- ---------------- --------------- ------ --------- ------ ------ --------------------------
| 1 | PRIMARY | tabname | ALL | NULL | NULL | NULL | NULL | 3 | Using where |
| 2 | DEPENDENT SUBQUERY | tabname | index_subquery | tid | tid | 5 | func | 1 | Using index; Using where |
---- -------------------- --------- ---------------- --------------- ------ --------- ------ ------ -------------------------- #range
代码语言：javascript复制 mysql> explain select * from tabname where tid between 1 and 2;
mysql> explain select * from tabname where id>1;
---- ------------- --------- ------- --------------- --------- --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------- --------------- --------- --------- ------ ------ -------------
| 1 | SIMPLE | tabname | range | PRIMARY | PRIMARY | 4 | NULL | 2 | Using where |
---- ------------- --------- ------- --------------- --------- --------- ------ ------ ------------- #index
代码语言：javascript复制mysql> explain select id,tid from tabname;
mysql> explain select tid from tabname;
---- ------------- --------- ------- --------------- ------ --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ -------------
| 1 | SIMPLE | tabname | index | NULL | tid | 5 | NULL | 3 | Using index |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ ------------- #ALL
代码语言：javascript复制 mysql> explain select * from tabname where tid<>2;
mysql> explain select * from tabname;
---- ------------- --------- ------ --------------- ------ --------- ------ ------ -------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------ --------------- ------ --------- ------ ------ -------
| 1 | SIMPLE | tabname | ALL | NULL | NULL | NULL | NULL | 3 | |
---- ------------- --------- ------ --------------- ------ --------- ------ ------ ------- 【Extra】
该列输出关MySQL如何解决查询的额外信息。（下面列出部分常见的）
Extra | Meaning |
|---|---|
usingwhere | 使用过滤条件 |
usingindex | 从索引树中查找所有列 |
usingtemporary | 使用临时表存储结果集，在使用groupby和orderby发生 |
selecttables optimized away | 没有groupby情况下使用min(),max(),或者count(*) |
usingfilesort | 有排序 |
notexists | 在leftjoin中匹配一行之后将不再继续查询查询 |
distinct | 查找到第一个匹配的行之后，MySQL则会停止对当前行的搜索 |
impossiblewhere | where子句总数失败的查询 |
impossiblehaving | having子句总数失败的查询 |
usingjoin buffer | 使用连接缓存 |
Usingindex for group-by | 与Usingindex类似，在使用group-by时可从索引中找到字段 |
#using where
代码语言：javascript复制 mysql> explain select * from tabname where id>2;
mysql> explain select * from tabname where tid=2;
---- ------------- --------- ------ --------------- ------ --------- ------- ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------ --------------- ------ --------- ------- ------ -------------
| 1 | SIMPLE | tabname | ref | tid | tid | 5 | const | 1 | Using where |
---- ------------- --------- ------ --------------- ------ --------- ------- ------ ------------- #using index
代码语言：javascript复制 mysql> explain select tid from tabname;
---- ------------- --------- ------- --------------- ------ --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ -------------
| 1 | SIMPLE | tabname | index | NULL | tid | 5 | NULL | 3 | Using index |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ ------------- #using temporary
代码语言：javascript复制 mysql> explain select distinct name from tabname;
---- ------------- --------- ------ --------------- ------ --------- ------ ------ -----------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------ --------------- ------ --------- ------ ------ -----------------
| 1 | SIMPLE | tabname | ALL | NULL | NULL | NULL | NULL | 3 | Using temporary |
---- ------------- --------- ------ --------------- ------ --------- ------ ------ ----------------- #select tables optimized away
代码语言：javascript复制 mysql> explain select max(tid) from tabname;
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------------------------
| 1 | SIMPLE | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Select tables optimized away |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------------------------ #using filesort
代码语言：javascript复制 mysql> explain select id,name from tabname group by id,name;
mysql> explain select * from tabname order by name;
---- ------------- --------- ------ --------------- ------ --------- ------ ------ ----------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------ --------------- ------ --------- ------ ------ ----------------
| 1 | SIMPLE | tabname | ALL | NULL | NULL | NULL | NULL | 3 | Using filesort |
---- ------------- --------- ------ --------------- ------ --------- ------ ------ ---------------- #not exists
代码语言：javascript复制 mysql> explain select * from tabname a left join tabname b on a.id=b.id where b.id is null;
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ -------------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ -------------------------
| 1 | SIMPLE | a | ALL | NULL | NULL | NULL | NULL | 3 | |
| 1 | SIMPLE | b | eq_ref | PRIMARY | PRIMARY | 4 | test.a.id | 1 | Using where; Not exists |
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ ------------------------- #distinct
代码语言：javascript复制mysql> explain select distinct a.id from tabname a left join tabname b on a.id=b.id;
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ ------------------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ ------------------------------
| 1 | SIMPLE | a | index | NULL | tid | 5 | NULL | 3 | Using index; Using temporary |
| 1 | SIMPLE | b | eq_ref | PRIMARY | PRIMARY | 4 | test.a.id | 1 | Using index; Distinct |
---- ------------- ------- -------- --------------- --------- --------- ----------- ------ ------------------------------ #impossible where
代码语言：javascript复制 mysql> explain select * from tabname where 1=2;
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------------
| 1 | SIMPLE | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------------ #impossible having
代码语言：javascript复制mysql> explain select id,count(*) from tabname group by id having 1=2;
mysql> explain select count(*) from tabname having 1=2;
---- ------------- ------- ------ --------------- ------ --------- ------ ------ -------------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ -------------------
| 1 | SIMPLE | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible HAVING |
---- ------------- ------- ------ --------------- ------ --------- ------ ------ ------------------- 现在使用 EXTENDED 情况：
语法：
- EXPLAIN EXTENDED <select statement>;
不使用 extended 和使用extended 的分析情况：
代码语言：javascript复制 mysql> explain select tid from tabname;
---- ------------- --------- ------- --------------- ------ --------- ------ ------ -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ -------------
| 1 | SIMPLE | tabname | index | NULL | tid | 5 | NULL | 3 | Using index |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ -------------
1 row in set (0.00 sec)
mysql> explain extended select tid from tabname;
---- ------------- --------- ------- --------------- ------ --------- ------ ------ ---------- -------------
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ ---------- -------------
| 1 | SIMPLE | tabname | index | NULL | tid | 5 | NULL | 3 | 100.00 | Using index |
---- ------------- --------- ------- --------------- ------ --------- ------ ------ ---------- -------------
1 row in set, 1 warning (0.00 sec) 可以看到，使用 extended 时，输出的最下面多了 1 条警告。 此时可以用 show warnings 来查看：
代码语言：javascript复制 mysql> show warnings G;
*************************** 1. row ***************************
Level: Note
Code: 1003
Message: select `test`.`tabname`.`tid` AS `tid` from `test`.`tabname`
1 row in set (0.00 sec)
ERROR:
No query specified show warnings 显示了优化器中是怎么规范表和字段名的，在通过重写和优化规则之后的 select 语句是什么样子。
更多参考：
EXPLAIN Output Format
EXPLAIN EXTENDED Output Format
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