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Operation	In-Place?	Rebuilds Table?	Permits Concurrent DML?	Only Modifies Metadata?	Notes
CREATE INDEX, ADD INDEX	Yes*	No*	Yes	No	Restrictions apply for FULLTEXT indexes; see next row.
ADD FULLTEXT INDEX	Yes*	No*	No	No	Adding the first FULLTEXT index rebuilds the table if there is no user-defined FTS_DOC_ID column. Subsequent FULLTEXT indexes may be added on the same table without rebuilding the table.
ADD SPATIAL INDEX	Yes	No	No	No
RENAME INDEX	Yes	No	Yes	Yes	Only modifies table metadata.
DROP INDEX	Yes	No	Yes	Yes	Only modifies table metadata.
OPTIMIZE TABLE	Yes*	Yes	Yes	No	In-place operation is not supported for tables with FULLTEXT indexes.
Set column default value	Yes	No	Yes	Yes	Only modifies table metadata.
Change auto-incrementvalue	Yes	No	Yes	No*	Modifies a value stored in memory, not the data file.
Add foreign key constraint	Yes*	No	Yes	Yes	The INPLACE algorithm is supported when foreign_key_checks is disabled. Otherwise, only theCOPY algorithm is supported.
Drop foreign key constraint	Yes	No	Yes	Yes	foreign_key_checks can be enabled or disabled.
Rename column	Yes*	No	Yes*	Yes	To permit concurrent DML, keep the same data type and only change the column name.ALGORITHM=INPLACE is not supported for renaming a generated column.
Add column	Yes*	Yes*	Yes*	No	Concurrent DML is not permitted when adding an auto-increment column. Data is reorganized substantially, making it an expensive operation. ALGORITHM=INPLACE is supported for adding a virtual generated column but not for adding a stored generated column. Adding a virtual generated column does not require a table rebuild.
Drop column	Yes	Yes*	Yes	No	Data is reorganized substantially, making it an expensive operation. ALGORITHM=INPLACE is supported for dropping a generated column. Dropping a virtual generated column does not require a table rebuild.
Reorder columns	Yes	Yes	Yes	No	Data is reorganized substantially, making it an expensive operation.
Change ROW_FORMATproperty	Yes	Yes	Yes	No	Data is reorganized substantially, making it an expensive operation.
Change KEY_BLOCK_SIZEproperty	Yes	Yes	Yes	No	Data is reorganized substantially, making it an expensive operation.
Make column NULL	Yes	Yes*	Yes	No	Rebuilds the table in place. Data is reorganized substantially, making it an expensive operation.
Make column NOT NULL	Yes*	Yes	Yes	No	Rebuilds the table in place. STRICT_ALL_TABLES or STRICT_TRANS_TABLES SQL_MODE is required for the operation to succeed. The operation fails if the column contains NULL values. The server prohibits changes to foreign key columns that have the potential to cause loss of referential integrity. SeeSection 13.1.8, “ALTER TABLE Syntax”. Data is reorganized substantially, making it an expensive operation.
Change column data type	No*	Yes	No	No	VARCHAR size may be increased using online ALTER TABLE. See Modifying Column Properties for more information.
Add primary key	Yes*	Yes*	Yes	No	Rebuilds the table in place. Data is reorganized substantially, making it an expensive operation.ALGORITHM=INPLACE is not permitted under certain conditions if columns have to be converted toNOT NULL.
Drop primary key and add another	Yes	Yes	Yes	No	Data is reorganized substantially, making it an expensive operation.
Drop primary key	No	Yes	No	No	Only ALGORITHM=COPY supports dropping a primary key without adding a new one in the same ALTER TABLE statement.
Convert character set	No	Yes*	No	No	Rebuilds the table if the new character encoding is different.
Specify character set	No	Yes*	No	No	Rebuilds the table if the new character encoding is different.
Rebuild with FORCE option	Yes*	Yes	Yes	No	Uses ALGORITHM=INPLACE. ALGORITHM=INPLACE is not supported for tables with FULLTEXT indexes.
“null” rebuild using ALTER TABLE ... ENGINE=INNODB	Yes*	Yes	Yes	No	Uses ALGORITHM=INPLACE. ALGORITHM=INPLACE is not supported for tables with FULLTEXT indexes.
Set STATS_PERSISTENT,STATS_AUTO_RECALC,STATS_SAMPLE_PAGESpersistent statistics options	Yes	No	Yes	Yes	Only modifies table metadata.
ALTER TABLE … ENCRYPTION	No	Yes	No	Yes
Drop a STORED column	Yes	Yes*	Yes	No	Rebuilds the table in place.
Modify STORED column order	Yes	Yes*	Yes	No	Rebuilds the table in place.
Add a STORED column	Yes	Yes*	Yes	No	Rebuilds the table in place.
Drop a VIRTUAL column	Yes	No	Yes	Yes
Modify VIRTUAL column order	Yes	No	Yes	Yes
Add a VIRTUAL column	Yes	No	Yes	Yes

此列顯示哪些操作允許使用ALGORITHM=INPLACE子句。“Rebuilds Table？”列顯示哪些操作可以重建表。對于使用就地算法的操作，表將就地重建。對于不支持就地算法的操作，使用表復(fù)制方法重新生成表。

“允許并發(fā)DML？”列顯示完全在線執(zhí)行的操作。您可以指定LOCK=NONE來斷言在DDL操作期間允許并發(fā)DML。MySQL在可能的情況下自動(dòng)允許并發(fā)DML。

在所有聯(lián)機(jī)DDL操作期間允許并發(fā)查詢。您可以指定LOCK=SHARED來斷言在DDL操作期間允許并發(fā)查詢。MySQL在可能的情況下自動(dòng)允許并發(fā)查詢。

“注釋”列提供附加信息，并解釋與其他列的“是/否”值相關(guān)的異常和依賴關(guān)系。星號(hào)表示異常或依賴項(xiàng)。

上述就是小編為大家分享的怎么理解MySQL 5.7 Online DDL Overview了，如果剛好有類似的疑惑，不妨參照上述分析進(jìn)行理解。如果想知道更多相關(guān)知識(shí)，歡迎關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道。

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