当调用spark session的sql方法时,SQL解析器首先将sql语句解析为ANTLR ParseTree,然后将ANTLR ParseTree转换为未解析的逻辑计划(Unresolved Logical Plan)。 然后将未解析的逻辑计划(Unresolved Logical Plan)传递到 Dataset 的 ofRows 方法中以创建 QueryExecution 实例。 def sql(sqlText: String): DataFrame = withAc...
本文专注于完成2022 CMU15445 Project #3 - Query Execution实验后的总结,主要是本人在实验所遇到的问题以及了解到的新知识,由于本人也是初学者,如有错误或不合理之处,请麻烦在评论区指出,共同学习进步。 Overview SQL 体系结构 在前几个实验中,主要是构建为了支持SQL语句执行的“部件”: 缓存池BufferPoolManager:负...
本次实验使用迭代模型,伪代码如下图所示: Bustub 使用执行引擎ExecutionEngine执行物理计划,这个类的代码很简洁,只有一个Execute()方法。可以看到这个方法会先将执行计划转换为对应的执行器executor,使用Init()初始化后循环调用executor的Next()方法获取查询结果: 复制classExecutionEngine{public:ExecutionEngine(BufferPoolMa...
Some query execution plans in Microsoft SQL Server include pattern of evaluating a filter on top of a table or index scan/range operation. Some parts of the filter predicate may match an index key and may therefore be used to ...
The following query gives the size of memory held by query execution (available in SQL Server 2000 SP1 only): select sum(total_memory_kb) from sys.dm_exec_query_resource_semaphores Note: please be cautious when using sys.dm_exec_query_memory_grants and sys.dm_exec_query_reso...
QUERY EXECUTION 再开始这个实验之前首先要搞懂几个类的定义和方法 Catalog.h Catalog用来维护一个数据库的元信息,包括表的信息,列的信息,索引的信息,用户和许可权等。在catalog.h文件中主要包含一下几点信息: std::unordered_map<table_oid_t,std::unique_ptr<TableInfo>> tables_;//用来维持一个table_id 到...
SQL Query Execution SQL Parsing The parser processes SQL strings and builds a tree representation of them. SeeParser. SQL Optimizer Stored Programs Prepared statements See mysql_stmt_prepare Stored procedures See sp_head, sp_instr. SQL Functions...
Flavien Charlon, a software developer on our adCenter team team recently wrote a series of articles on his blog after completing SQL Server training by Kimberly Tripp. Each blog post outlines the different query execution plans. Part 1: SQL Server Data Structures In SQL Server, data is ...
Use this page to specify the options for running Microsoft SQL Server queries. To access this dialog box, right-click the body of a Query Editor window, and then selectQuery Optionsor on theToolsmenu, selectOptions, then theQuery Executionfolder. ...
The SQL order of execution defines the order in which the clauses of a query are evaluated. Some of the most common query challenges people run into could be easily avoided with a clearer understanding of the SQL order of execution, sometimes called the SQL order of operations. Understanding ...