标签：模糊 获取 code using 删除 can 引入 有关 operation
原文地址：https://mysqlserverteam.com/mysql-8-0-innodb-now-supports-instant-add-column/
MySQL 5.6是第一个支持INPLACE DDL的版本。在MySQL 5.6之前，执行DDL的唯一方法是逐行复制行。
INPLACE DDL主要由InnoDB处理，而逐行COPY在服务器层处理。直到8.0（请参阅实验版本），InnoDB甚至通过为INPLACE DDL算法重建表来向表中添加列。
许多用户向我们询问了如何避免耗时的schema changes。现在，可以通过（始终）指定ALGORITHM = INSTANT来实现，这将保证操作立即完成（如果不支持则无法完成）。
此外，如果根本未指定ALGORITHM，则服务器将首先尝试DEFAULT = INSTANT算法，如果无法完成，则服务器将尝试INPLACE算法；如果SE无法支持，服务器将最终尝试COPY算法。
新语法如下：
ALTER TABLE table_name [alter_specification], ALGORITHM=INSTANT;
ALTER TABLE t1 ALTER COLUMN i SET DEFAULT 11, ALGORITHM=INSTANT, LOCK=NONE; ERROR HY000: Incorrect usage of ALGORITHM=INSTANT and LOCK=NONE/SHARED/EXCLUSIVE # ALGORITHM=INSTANT and LOCK=DEFAULT are OK though. ALTER TABLE t1 ALTER COLUMN i SET DEFAULT 13, ALGORITHM=INSTANT, LOCK=DEFAULT;
ALTER TABLE t1 ALTER COLUMN i SET DEFAULT 12, DROP COLUMN j, ALGORITHM=INSTANT; ERROR 0A000: ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=COPY/INPLACE
当前,Innodb的即时DDL支持如下操作
mysql> CREATE TABLE t1 (a INT, b INT, KEY(b)); Query OK, 0 rows affected (0.70 sec) mysql> # Modify the index can be instant if it‘s a trivial change mysql> ALTER TABLE t1 DROP KEY b, ADD KEY b(b) USING BTREE, ALGORITHM = INSTANT; Query OK, 0 rows affected (0.14 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> # Rename the table through ALTER TABLE can be instant mysql> ALTER TABLE t1 RENAME TO t2, ALGORITHM = INSTANT; Query OK, 0 rows affected (0.26 sec) mysql> # SET DEFAULT to a column can be instant mysql> ALTER TABLE t2 ALTER COLUMN b SET DEFAULT 100, ALGORITHM = INSTANT; Query OK, 0 rows affected (0.09 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> # DROP DEFAULT to a column can be instant mysql> ALTER TABLE t2 ALTER COLUMN b DROP DEFAULT, ALGORITHM = INSTANT; Query OK, 0 rows affected (0.08 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> # MODIFY COLUMN can be instant mysql> ALTER TABLE t2 ADD COLUMN c ENUM(‘a‘, ‘b‘, ‘c‘), ALGORITHM = INSTANT; Query OK, 0 rows affected (0.35 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE t2 MODIFY COLUMN c ENUM(‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘), ALGORITHM=INSTANT; Query OK, 0 rows affected (0.12 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> # ADD/DROP virtual column can be instant mysql> ALTER TABLE t2 ADD COLUMN (d INT GENERATED ALWAYS AS (a + 1) VIRTUAL), ALGORITHM = INSTANT; Query OK, 0 rows affected (0.38 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE t2 DROP COLUMN d, ALGORITHM = INSTANT; Query OK, 0 rows affected (0.40 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> # Do two operations instantly in the same statement mysql> ALTER TABLE t2 ALTER COLUMN a SET DEFAULT 20, ALTER COLUMN b SET DEFAULT 200, ALGORITHM = INSTANT; Query OK, 0 rows affected (0.20 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> DROP TABLE t2; Query OK, 0 rows affected (0.36 sec)
2，“即时”加字段的过程：基于行的存储规则发生变化之后（增加字段），仅修改元数据
,
3，“即时”加字段之后，查询的处理过程。
4，“即时”加字段后，新增数据的处理
mysql> CREATE TABLE t1 (a INT, b INT); Query OK, 0 rows affected (0.06 sec) mysql> SELECT table_id, name, instant_cols FROM information_schema.innodb_tables WHERE name LIKE ‘%t1%‘; +----------+---------+--------------+ | table_id | name | instant_cols | +----------+---------+--------------+ | 1065 | test/t1 | 0 | +----------+---------+--------------+ 1 row in set (0.22 sec) mysql> SELECT table_id, name, has_default, default_value FROM information_schema.innodb_columns WHERE table_id = 1065; +----------+------+-------------+---------------+ | table_id | name | has_default | default_value | +----------+------+-------------+---------------+ | 1065 | a | 0 | NULL | | 1065 | b | 0 | NULL | +----------+------+-------------+---------------+ 2 rows in set (0.38 sec)
mysql> ALTER TABLE t1 ADD COLUMN c INT, ADD COLUMN d INT DEFAULT 1000, ALGORITHM=INSTANT; Query OK, 0 rows affected (0.07 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> SELECT table_id, name, instant_cols FROM information_schema.innodb_tables WHERE name LIKE ‘%t1%‘; +----------+---------+--------------+ | table_id | name | instant_cols | +----------+---------+--------------+ | 1065 | test/t1 | 2 | +----------+---------+--------------+ 1 row in set (0.03 sec) mysql> SELECT table_id, name, has_default, default_value FROM information_schema.innodb_columns WHERE table_id = 1065; +----------+------+-------------+---------------+ | table_id | name | has_default | default_value | +----------+------+-------------+---------------+ | 1065 | a | 0 | NULL | | 1065 | b | 0 | NULL | | 1065 | c | 1 | NULL | | 1065 | d | 1 | 800003e8 | +----------+------+-------------+---------------+ 4 rows in set (0.36 sec)
mysql> ALTER TABLE t1 ADD COLUMN e VARCHAR(100) DEFAULT ‘Hello MySQL!‘; Query OK, 0 rows affected (0.06 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> SELECT table_id, name, instant_cols FROM information_schema.innodb_tables WHERE name LIKE ‘%t1%‘; +----------+---------+--------------+ | table_id | name | instant_cols | +----------+---------+--------------+ | 1065 | test/t1 | 2 | +----------+---------+--------------+ 1 row in set (0.03 sec) mysql> SELECT table_id, name, has_default, default_value FROM information_schema.innodb_columns WHERE table_id = 1065; +----------+------+-------------+--------------------------+ | table_id | name | has_default | default_value | +----------+------+-------------+--------------------------+ | 1065 | a | 0 | NULL | | 1065 | b | 0 | NULL | | 1065 | c | 1 | NULL | | 1065 | d | 1 | 800003e8 | | 1065 | e | 1 | 48656c6c6f204d7953514c21 | +----------+------+-------------+--------------------------+ 5 rows in set (0.36 sec)
MySQL 8.0 InnoDB对即时加字段的会支持（instant add column）（译）
标签：模糊 获取 code using 删除 can 引入 有关 operation
原文地址：https://www.cnblogs.com/wy123/p/12875778.html
