mysql - 如何检查MySQL中当前的MERGE_THRESHOLD值？

Question

我们可以在创建表/索引时设置一个新变量，即MERGE_THRESHOLD。

其描述在这里: Merge threshold for innodb index pages

但是如何检查merge_threshold的当前值呢？

我像检查其他变量一样使用了这个查询，但没有成功。

show variables like 'MERGE_THRESHOLD' ;

Answer 1

答案可以在您的 MySQL 文档中找到 linked in your question :

The current MERGE_THRESHOLD value for an index can be obtained by querying the INNODB_SYS_INDEXES table. For example:

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_INDEXES WHERE
NAME='id_index' \G
*************************** 1. row ***************************
       INDEX_ID: 91
           NAME: id_index
       TABLE_ID: 68
           TYPE: 0
       N_FIELDS: 1
        PAGE_NO: 4
          SPACE: 57
MERGE_THRESHOLD: 40

You can use SHOW CREATE TABLE to view the MERGE_THRESHOLD value for a table, if explicitly defined using the table_option COMMENT clause:

mysql> SHOW CREATE TABLE t2 \G
*************************** 1. row ***************************
       Table: t2 Create Table: CREATE TABLE `t2` (   `id` int(11) DEFAULT NULL,   KEY `id_index` (`id`) COMMENT 'MERGE_THRESHOLD=40' )
ENGINE=InnoDB DEFAULT CHARSET=latin1