If the table schema changes, both the FE node version and SE version need to be updated. If the FE node version and SE version are inconsistent with the schema version, schema latency may occur. If a large number of DDL statements are executed on the partitioned parent table, the ...
5、possible_keys possible_keys是指在这个SQL中,mysql可以使用这个索引去辅助查找记录,当查询涉及到的字段,都会被列出,但不一定被查询使用.若为空则表示没有可以使用的索引,此时可以通过检查where语句看是否可以引用某些列或者新建索引来提高性能。 6、key(重要) key列显示的是当前表实际使用的索引,如果没有选择索引...
The EXPLAIN command will fail if you use it for other SQL commands, such as data definition language (DDL) or database operations. The EXPLAIN output relative unit costs are used by Amazon Redshift to choose a query plan. Amazon Redshift compares the sizes of various resource estimates to ...
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Benefrancis / system-design-101 Public forked from ByteByteGoHq/system-design-101 Notifications You must be signed in to change notification settings Fork 0 Star 0 Explain complex systems using visuals and simple terms. Help you prepare for system design interviews. ...