If a secondary index is not present, InnoDB processes SELECT COUNT(*) statements by scanning the clustered index. And how do we measure the cost of such a counting query? Is it like any other query type? With a simple sysbench table example, first let’s check the query plan:...
Clustered Indexes (SQL Server, MySQL/InnoDB) SQL Server and MySQL (using InnoDB) take a broader view of what “index” means. They refer to tables that consist of the index structure only asclustered indexes. These tables are called Index-Organized Tables (IOT) in the Oracle database. ...
Structured Query Language (SQL) is a standardized language used in computer programming to handle databases. Learn about queries in SQL, and ponder...
It now checks for a valid R-tree structure and ensures that the entry count matches up with the clustered index. See also Jimmy Yang’s article “InnoDB Spatial Indexes in 5.7.4 LAB release“. GIS: Geometry Functions & Formats After a careful evaluation of various open source geometry ...
The index lock that was used to protect the entire index tree structure is now replaced by more fine grained “block locks” in the tree. See Yasufumi Kinoshita’s article “MySQL-5.7 improves DML oriented workloads“. InnoDB Faster & Parallel Flushing. We have reduced the number of pages ...
Learn how to use the MySQL OCTET_LENGTH function to retrieve the length of a string in bytes. Discover its syntax, examples, and applications.
InnoDB 目前支持在 clustered index 上进行并行查询,提供 innodb_parallel_read_threads 参数控制session内的并行度。 11、Redo优化 Redo的写入一直是 InnoDB 高并发情况下的瓶颈,8.0 开始: 1)用户线程可以并发的copy redo 日志到 log buffer中 2)用户线程可以以更松散的方式把 dirty block 加入到脏块链表中 ...
“Unable to enlist in the transaction” with Oracle linked server from MS SQL Server [<Name of Missing Index, sysname,>] in non clustered index [Execute SQL Task] Error: The value type (__ComObject) can only be converted to variables of type Object. [ODBC Driver Manager] Data source n...
Add basic support for hierarchyid type in SQL Server. SSMA v8.2 The v8.2 release of SSMA for MySQL is enhanced with a targeted set of fixes designed to improve quality and conversion metrics, and fixes for: An issue with disabled nonclustered indexes after data migration. Detection of .NET ...
AFAIK, Cancel will try really hard to cancel the query similar to the "Stop" button in SQL Server Management Studio. I suppose it is possible that the query has "just" completed; when you call Cancel, you really will not know for sure if it got cancelled or if it "just" completed. ...