因为MySQL是索引组织表,索引优化是SQL语句常用的主要必要手段。普遍情况下执行计划都是能合理选择最优的索引,进行检索。但也有例外。 在官方Note提示后期就会弃掉,融合到Optimizer Hints里。要是在代码中使用索引Hint就要注意了。 说明:USE INDEX、FORCE INDEX和IGNORE INDEX将在MySQL的未来版本中被弃用,并在之后的某...
0 bytes received via SQL*Net from client 0 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) rows processed Hints是Oracle提供的一个辅助用法,按字面理解就是‘提示’的意思,确实它起得作用也是提示优化器按它所提供的关键字来选择执行路径,特别适用于sql调整的时候。使用方法如下: {DEL...
You can specify multiple index hints: SELECT*FROMt1USEINDEX(i1)IGNOREINDEXFORORDERBY(i2)ORDERBYa; It is not an error to name the same index in several hints (even within the same hint): SELECT*FROMt1USEINDEX(i1)USEINDEX(i1,i1); ...
LOCALINDEX和HINT的使用【DO BE USED LOCALINDEXINHINT】 今晚(当然还差14分钟就到明天了),对一张有19956517条记录的表进行特定SQL的优化操作。问题很快解决,原本需要56秒到1分半左右得到结果集的SQL,现在小于0.3秒。其实问题很简单,分裂(SPLIT)PARTITION后,没有及时更新本地索引!【如果有兴趣可以看看我写的有关分...
This means they might be selected by the query optimizer and, if necessary, specified in index hints. Target The target or targets is the new index (or heap) or a set of new indexes that is being created or rebuilt. User insert, update, and delete operations to the source are applied ...
Okay. I think it makes sense to support force (and probably ignore too in that case). Here's an API proposal: We add anindexHintsproperty to the sequelize options. db.User.findOne({ where: { email: "joe@example.com", }, indexHints: [ { type: "use", values: ["i1"] } ], }...
https://dev.mysql.com/doc/refman/8.0/en/optimizer-hints.html 一、 /* ... */ 在大部分语言中都一样是注释。这个之中的语句是不被执行的。 但MYSQL中 为了保持兼容,比如从mysqldump 导出的SQL语句能被其它数据库直接使用,它把一些特有的仅在MYSQL上的语句放在 /*! ... */ 中,这样这些语句如果在其它...
Also read:MySQL USE INDEX For Index Hints Introduction to MySQL FORCE INDEX As you know, whenever there is anindexavailable on the table, the query optimizer tries to utilize it for fetching the records in the most optimal way. The query optimizer will always try to come up with the most...
hints extensible optimization, 21-18 PARALLEL, 23-17 PARALLEL_INDEX, 23-17 histograms, 21-9 historical database maintenance operations, 11-47 partitions, 11-6 HP's OpenView, 30-33 I IBM's NetView/6000, 30-33 ILMS, 15-21 immediate constraints, 25-24 IMP_FULL_DATABAS...
SqlServer.TransactSql.ScriptDom Microsoft.SqlServer.TransactSql.ScriptDom AbortAfterWaitType AcceleratedDatabaseRecoveryDatabaseOption AddAlterFullTextIndexAction AddFileSpec AddMemberAlterRoleAction AddSearchPropertyListAction AddSensitivityClassificationStatement AddSignatureStatement AdHocDataSource AdHocTableReferenc...