spark sql join optimization

(list);DataFrame RESULT_DF = Sqlcontext.createdataframe (Result_rdd_row, ST);Result_df.javardd (). foreach (new voidfunctionPrivate static final long serialversionuid = 1L; @Overridepublic void call (Row row) throws Exception {String sql = "INSERT into Good_student_infos values ("+ "'" + string.valueof (row.getstring (0)) + "',"+ integer.valueof (string.valueof (Row.get (1)) + ","+ integer.valueof (string.valueof (Row.get (2)) + ")";SYSTEM.OUT.PRINTL

Boss said that the usual query data large data to avoid using the join would rather once the data of a table to find out to use this data to do the query and do not use too much of the join as much as possible into the query to do, please the big God to say that the SQL optimization Reply content: Boss said that t

;setautottraceonly sql>select*frombig_empa,dept_new bwherea.deptno=b.deptno; 917504rowsselected. Executionplan----------------------------------------------------------planhashvalue: 1925493178-------------------------------------------------------------------------------|id |operation |name|rows|bytes |Cost (%CPU) |time| -------------------------------------------------------------------------------|0|selectstatement| |917k|54m|1490 (2) | 00:00:18

MySQL Using temporary; Using filesort inner join optimization, filesortinnerProblem Using the show full processlist statement, you can easily find the problematic SQL statement, as shown below: SELECT post.*FROM postINNER JOIN post_tag ON post.id = post_tag.post_idWHERE post.status = 1 AND post_tag.tag_id = 123ORDER BY

The original SQL statement is as follows: SELECT o.order_id FROM orders o JOIN shipping_orders so ON so.order_id = o.order_id JOIN shippings s ON s.shipping_no = so.shipping_no WHERE o.payment_method = 'COD'AND o.status IN(3, 4, 6, 11, 12)AND s.logistic_track_no shipping_ordersTable andshippingsTable Associ

(packaging warehouse, 0) packaging warehouse, nvl (packaging, 0) packaging from (SELECT WO_CODE AS WoCode, sum (USED_QTY) AS UsedQty FROM T_SN2UPN where (mat_code like 'mfy % 'OR mat_code like 'emby % ') and MDATE> = to_date ('2017-04-27 ', 'yyyy-mm-dd hh24: mi: ss ') and mdate This SQL statement is olap and runs on oracle10g. It takes 33 seconds to run each time. Generally, olap reports require the best customer experience within 5 seconds. Note t

full outer join, a Cartesian product, and so on.　　Well, since the SQL execution plan has been parsed, it's time to optimize the parsed execution plan, and the parsing process will parse the SQL for a unresolved Logicalplan tree. Down Analyzer and optimizer will add a variety of analysis and optimization operations to

Although the previous article introduced the Native_full_outer_join and no_native_full_outer_join two hint, but in fact Native_full_outer_join did not play any role, Because Oracle's optimization of the full outer join makes the new execution plan less costly than the original execution plan, Oracle chooses the execution plan by default, so it does not see the effect of the native_full_outer_join hint.

MySQL Query Optimization: connection query sorting limit (join, orderby, limit statement) introduces bitsCN.com. I don't know if anyone has encountered such a disgusting problem: two tables are connected for query and limit, SQL efficiency is very high, but after order by is added, the execution time of the statement becomes very long, and the efficiency is very

Database optimization and SQL optimization summary, SQL optimization SummaryDatabase Optimization Methods1. select the most suitable field attribute MySQL can support access to large data volumes, but generally, the smaller the ta

of poor performance connectivity by reducing query scope from a business perspective.Reference documents:http://msdn.microsoft.com/zh-cn/library/aa178403 (v=sql.80). aspx Http://www.dbsophic.com/SQL-Server-Articles/physical-join-operators-merge-operator.htmlIn a SQL Server database, the query optimizer typically uses

* from Salary")1, the number of departmental staff inquiriesFirst, the People table data and the Department table data join operation, and then according to Department department name grouping, after grouping for the people in the unique identification of a worker's ID field for statistics, and finally get the total number of employees in each department statistics information.Scala > Sqlcontext.sql ("Select B.name,count (a.id) from people a joins De