重要

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如无特殊需求,建议使用 TiDB 数据库的最新 LTS 版本

ADD INDEX

ALTER TABLE.. ADD INDEX 语句用于在已有表中添加一个索引。在 TiDB 中,ADD INDEX 为在线操作,不会阻塞表中的数据读写。

警告
  • 在升级 TiDB 集群的过程中,请勿执行 DDL 语句,否则可能会出现行为未定义的问题。
  • 集群中有 DDL 语句正在被执行时(通常为 ADD INDEX 和列类型变更等耗时较久的 DDL 语句),请勿进行升级操作。在升级前,建议使用 ADMIN SHOW DDL 命令查看集群中是否有正在进行的 DDL Job。如需升级,请等待 DDL 执行完成或使用 ADMIN CANCEL DDL 命令取消该 DDL Job 后再进行升级。

语法图

AlterTableStmt
ALTERIgnoreOptionalTABLETableNameAlterTableSpecListOptAlterTablePartitionOptANALYZEPARTITIONPartitionNameListINDEXIndexNameListAnalyzeOptionListOpt
AlterTableSpec
TableOptionListSETTIFLASHREPLICALengthNumLocationLabelListCONVERTTOCharsetKwCharsetNameDEFAULTOptCollateADDColumnKeywordOptIfNotExistsColumnDefColumnPosition(TableElementList)ConstraintPARTITIONIfNotExistsNoWriteToBinLogAliasOptPartitionDefinitionListOptPARTITIONSNUMCHECKTRUNCATEPARTITIONOPTIMIZEREPAIRREBUILDPARTITIONNoWriteToBinLogAliasOptAllOrPartitionNameListCOALESCEPARTITIONNoWriteToBinLogAliasOptNUMDROPColumnKeywordOptIfExistsColumnNameRestrictOrCascadeOptPRIMARYKEYPARTITIONIfExistsPartitionNameListKeyOrIndexIfExistsCHECKIdentifierFOREIGNKEYIfExistsSymbolEXCHANGEPARTITIONIdentifierWITHTABLETableNameWithValidationOptIMPORTDISCARDPARTITIONAllOrPartitionNameListTABLESPACEREORGANIZEPARTITIONNoWriteToBinLogAliasOptReorganizePartitionRuleOptORDERBYAlterOrderItem,DISABLEENABLEKEYSMODIFYColumnKeywordOptIfExistsCHANGEColumnKeywordOptIfExistsColumnNameColumnDefColumnPositionALTERColumnKeywordOptColumnNameSETDEFAULTSignedLiteral(Expression)DROPDEFAULTCHECKIdentifierEnforcedOrNotINDEXIdentifierIndexInvisibleRENAMECOLUMNKeyOrIndexIdentifierTOIdentifierTO=ASTableNameLockClauseAlgorithmClauseFORCEWITHWITHOUTVALIDATIONSECONDARY_LOADSECONDARY_UNLOAD
Constraint
ConstraintKeywordOptConstraintElem
ConstraintKeywordOpt
CONSTRAINTSymbol
ConstraintElem
PRIMARYKEYKeyOrIndexIfNotExistsUNIQUEKeyOrIndexOptIndexNameAndTypeOptFULLTEXTKeyOrIndexOptIndexName(IndexPartSpecificationList)IndexOptionListFOREIGNKEYIfNotExistsIndexName(IndexPartSpecificationList)ReferDefCHECK(Expression)EnforcedOrNotOpt
IndexNameAndTypeOpt
IndexNameUSINGIndexTypeNameIdentifierTYPEIndexTypeName
IndexPartSpecificationList
IndexPartSpecification,
IndexPartSpecification
ColumnNameOptFieldLen(Expression)Order
IndexOptionList
IndexOption
IndexOption
KEY_BLOCK_SIZE=LengthNumIndexTypeWITHPARSERIdentifierCOMMENTstringLitIndexInvisible
KeyOrIndex
KEYINDEX
IndexKeyTypeOpt
UNIQUESPATIALFULLTEXT
IndexInvisible
VISIBLEINVISIBLE
IndexTypeName
BTREEHASHRTREE

示例

CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL);
Query OK, 0 rows affected (0.11 sec)
INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5);
Query OK, 5 rows affected (0.03 sec)
Records: 5  Duplicates: 0  Warnings: 0
EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
+-------------------------+----------+-----------+---------------+--------------------------------+
| id                      | estRows  | task      | access object | operator info                  |
+-------------------------+----------+-----------+---------------+--------------------------------+
| TableReader_7           | 10.00    | root      |               | data:Selection_6               |
| └─Selection_6           | 10.00    | cop[tikv] |               | eq(test.t1.c1, 3)              |
|   └─TableFullScan_5     | 10000.00 | cop[tikv] | table:t1      | keep order:false, stats:pseudo |
+-------------------------+----------+-----------+---------------+--------------------------------+
3 rows in set (0.00 sec)
ALTER TABLE t1 ADD INDEX (c1);
Query OK, 0 rows affected (0.30 sec)
EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
+------------------------+---------+-----------+------------------------+---------------------------------------------+
| id                     | estRows | task      | access object          | operator info                               |
+------------------------+---------+-----------+------------------------+---------------------------------------------+
| IndexReader_6          | 0.01    | root      |                        | index:IndexRangeScan_5                      |
| └─IndexRangeScan_5     | 0.01    | cop[tikv] | table:t1, index:c1(c1) | range:[3,3], keep order:false, stats:pseudo |
+------------------------+---------+-----------+------------------------+---------------------------------------------+
2 rows in set (0.00 sec)

MySQL 兼容性

  • 不支持 FULLTEXTHASHSPATIAL 索引。
  • 不支持降序索引(类似于 MySQL 5.7)。
  • 目前尚不支持在一条中同时添加多个索引。
  • 无法向表中添加 CLUSTERED 类型的 PRIMARY KEY。要了解关于 CLUSTERED 主键的详细信息,请参考聚簇索引

另请参阅

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