Index Sequential Access Method (ISAM)Tree-based IndexingTree-based IndexingTree-based IndexingTree-based IndexingSpringer USdoi:10.1007/978-0-387-39940-9_2835
(ICP_OUT_OF_RANGE),goto idx_cond_failed row_search_idx_cond_check(buf, prebuilt, rec, offsets) if (index != clust_index && prebuilt->need_to_access_clustered) { requires_clust_rec: // 必要的话,拿到主键索引的记录行(如果使用的是二级索引查询) row_sel_get_clust_rec_for_mysql } //...
1.2 PG的逻辑结构 Database cluster(数据库集簇): 由postgresql server管理的数据库的集合,下面由多个database组成。一个数据库集簇可以包含多个Database、多个User,每个Database以及Database中的所有对象都有它们的所有者:User。 Database数据库:Postgres 默认数据库、Template0 最精简模板、Template1 默认模板;数据库...
Page locks are allowed when you access the index. The Database Engine determines when page locks are used. OFF Page locks aren't used. OPTIMIZE_FOR_SEQUENTIAL_KEY = { ON | OFF } Applies to: SQL Server 2019 (15.x) and later versions, Azure SQL Database, and Azure SQL Managed Instance...
Page locks are allowed when you access the index. The Database Engine determines when page locks are used. OFF Page locks aren't used. OPTIMIZE_FOR_SEQUENTIAL_KEY = { ON | OFF } Applies to: SQL Server 2019 (15.x) and later versions, Azure SQL Database, and Azure SQL Managed Instance...
(Sch-M) lock on the table. This prevents all user access to the underlying table during the operation. An offline index operation that creates a nonclustered index acquires a Shared (S) lock on the table. This prevents updates to the underlying table but allows read operations, such as...
High Waits on 'Db File Sequential Read' Due to Table Lookup Following Index Access (文档 ID 875472.1) 即使执行计划已经是最优的了,但一次查询仍能够等待“db file sequential read'”这种事件很长的时间。通常是因为索引扫描的结果集非常大。例如: ...
This method throws an error if ScriptData is true (Inherited from SqlSmoObject) SetAccessToken(IRenewableToken) Set the accessToken for connection. (Inherited from SqlSmoObject) SetCollectionTextMode(Boolean, SmoCollectionBase) (Inherited from ScriptNameObjectBase) SetIsSystemNamed(Boolean) (...
Large numbers of indexes can help the performance of queries that don't modify data, such as SELECT statements, because the query optimizer has more indexes to choose from to determine the fastest access method. Indexing small tables might not be optimal because it can take the query optimizer...
This prevents all user access to the underlying table during the operation. An offline index operation that creates, rebuilds, or drops a clustered index, or rebuilds or drops a nonclustered index, acquires a Schema modification (Sch-M) lock on the table. This prevents all user access to ...