Example The following example runscursor.explain()in"executionStats"verbosity mode to return the query planning and execution information for the specifieddb.collection.find()operation: db.products.find( {quant
The SQL Explain Plan option generates an explain plan for a query. To generate an explain plan, either highlight a query, or if nothing is highlighted and the language type is SQL mode, separate the queries in the editor by semi-colons and position the cursor within the query to explain,...
在RDBMS中,无论那种数据库,都提供了SQL剖析工具,用来解决SQL效率低下的问题。在MongoDB中,也有相应的策略来实现剖析。MongoDB提供了db.collection.explain()方法, cursor.explain()方法,和explain命令去返回查询计划信息和查询计划的执行统计信息。这为我们诊断...
ExplainOneQuery(Query *query, int cursorOptions, IntoClause *into, ExplainState *es, const char *queryString, ParamListInfo params, QueryEnvironment *queryEnv){ /* planner will not cope with utility statements */ if (query->commandType == CMD_UTILITY) { ExplainOneUtility(query->utilityStmt, ...
In mongosh, this command can also be run through the db.collection.explain() and cursor.explain() helper methods. Helper methods are convenient for mongosh users, but they may not return the same level of information as database commands. In cases where the convenience is not needed or the...
DECLARE cur_schema_names CURSOR FOR SELECT schema_name_table.schema_name FROM schema_name_table; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE; OPEN cur_schema_names; explain_loop: LOOP FETCH cur_schema_names INTO schema_name; ...
SQL>-- This script uses dbms_xplan.display_cursor SQL>@pln DataTypeTest PLAN_TABLE_OUTPUT --- SQL_ID 2va424cgs3sfb, child number 0 --- select /* DataTypeTest */ * from regions2 where region_id = :regid Plan hash value: 670750275 ---...
V$SQL_PLAN - A dynamic performance view that shows the execution plan for a SQL statement that has been compiled into a cursor and stored in the cursor cache. Under certain conditions the plan shown when using EXPLAIN PLAN can be different from the plan shown using V$SQL_PLAN. For example...
(a) Describe the concept of a cursor. (b) How is it used in embedded SQL? For a "Hello world" program, the kernel must copy the string from the user program memory to the screen memory. Why must the screen's buffer memory be protected?
Can someone explain pivot tables like I'm 5? I am not a data person and I can follow step-by-step instructions, but I cannot figure out how to get a certain type of answer when left to my own devices.