spark sql join optimization

launched, there were about 400 outgoing data records. The user simply timed out on the front end, and it took about 10 seconds to wait. the user experience was already poor. Take out the query SQL as follows: SELECT *FROM (SELECT DISTINCT leaveinfo.id, f_sqrgh, f_sqrbm, f_sqr, f_sqbmbm, f_sqbm, f_lxdhfj, f_sjhm, f_sqrq, f_rzrq, f_ndlzrq, f_qrlzrq, f_zw, f_gw, f_gwlx, f_gwcj, f_szdq, f_gzdd, f_lzyy, f_lzyyzs, f_yggxbmtjl, f_lzlx, f_inputtype, belongCo

copy of the original table, but in fact each server has only one member table and a distributed partition view. The data location is transparent to the application. 11. Rebuild the index dbcc reindex, dbcc indexdefrag, shrink data and log dbcc shrinkdb, and dbcc shrinkfile. set automatic log shrinking. for large databases, do not set Automatic database growth, which will reduce the server performance. The writing of T-SQL is very important. The follo

Oracle table connection modes (SQL optimization) 1. NESTED LOOP For a small subset of connected data, nested loop connection is a good choice. The nested loop is used to scan a table. Every time a record is read, it is searched in another table based on the index. Without an index, it is generally not nested loops. Generally, in the nested loop, the result set of the driver table meeting the condition is no

Oracle table three connection methods (SQL optimization), oraclesql 1. NESTED LOOP For a small subset of connected data, nested loop connection is a good choice. The nested loop is used to scan a table. Every time a record is read, it is searched in another table based on the index. Without an index, it is generally not nested loops. Generally, in the nested loop, the result set of the driver table meeting

to see which method works better. 28. Set NOCOUNT on at the beginning of all stored procedures and triggers, set NOCOUNT OFF at the end. You do not need to send a DONE_IN_PROC message to the client after each statement that executes the stored procedure and trigger. try to avoid large transaction operations and improve system concurrency. 30. Try to avoid the return of large data to the client, if the amount of data is too large, should consider whether the corresponding demand is reasonabl

execute where Filtering is a smart solution, and now to rule out MySQL query optimization, I write an optimized SQL0and Sc.score = + ) T INNER JOIN Student s on t.s_id = s.s_id That is, the SC table filtering, then table connection, the execution time is: 0.054s It's about the same time you didn't build s_id index before. To view the execution plan: First, the SC re-list is extracted, so the efficiency

, you can also add a table dedicated to paging, you can use a daemon to maintain. update pagination T join ( select ID, ceil (p:= p + 1 ) Span style= "color: #808080;" >/ $perpage) page from test order by ID) C on c.id = t.id set t.page = c.page; now it's easy to get an element of any page: SELECT * from Test A JOIN on a.ID=b.id WHERE page=$offset; There are a lot of tricks in

optimizer will list several possible connection solutions based on the connection conditions and find the best solution with the minimum system overhead. The join conditions must fully consider the tables with indexes and tables with multiple rows. The selection of the internal and external tables can be determined by the formula: Number of matched rows in the outer table * Number of times each query is performed in the inner table, the minimum produ

a copy of the original table, but there is only one member table and one distributed partitioned view on each server. The location of the data is transparent to the application.11. Rebuild the index DBCC REINDEX, DBCC INDEXDEFRAG, shrink data and log DBCC SHRINKDB,DBCC shrinkfile. Sets the auto-shrink log. For large databases do not set the database autogrow, it will degrade the performance of the server. There's a lot of emphasis on T-SQL, and here'

I. Operator Optimization 1. In Operator SQL statements written in are easy to write and understand, which is suitable for modern software development. However, SQL statements using in always have low performance. The following differences exist between SQL statements using in and

I. Operator Optimization 1. In Operator SQL statements written in are easy to write and understand, which is suitable for modern software development. However, SQL statements using in always have low performance. The following differences exist between SQL statements using in and

Oracle SQL Performance Optimization (1) select the most efficient table name sequence (only valid in the rule-based Optimizer ): The ORACLE parser processes the table names in the FROM clause in the order FROM right to left. The table written in the FROM clause (basic table driving table) will be processed first, when the FROM clause contains multiple tables, You must select the table with the least number

Tags: blog http using strong file dataSource: http://www.cnblogs.com/yunfeifei/p/3850440.htmThere are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but also please correct the supplement. This article I spent a lot of time looking for information, modification, typesetting, I hope yo

Add by Zhj: The author does not specify which database, which is just an approximate general summary. For a particular database, some entries may not be applicable.Original: http://www.cnblogs.com/yunfeifei/p/3850440.htmlThere are a lot of tutorials on SQL optimization online, but it's messy. Recently there is a time to tidy up a bit, write to share with you, where there are errors and deficiencies, but als

Tags: des blog http io ar os using SP forHttp://www.cnblogs.com/sopost/archive/2010/10/11/2190076.html in the SQL statement optimization process, we often use the hint, now summarize the SQL optimization process common Oracle Usage of hint:1./*+all_rows*/Indicates that the cost-based

oracle| Performance | optimization | statement 1. Choose the appropriate Oracle OptimizerOracle's optimizer total of 3 kinds A, rule (rule-based) B, cost (based on costs) C, CHOOSE (optional) set the default optimizer to pass various declarations of optimizer_mode parameters in the Init.ora file, such as Rule,cost,choose,all_rows,first_rows. You will of course overwrite it at the SQL sentence level or at th

of the various connections are: The inner join result set size depends on the number of conditions that the left and right tables meet Left join depends on the size of the left table, right opposite. Total connection and cross-connect depending on the amount of data in the two tables left and right SELECT * FROM ((SELECT * from Orde where orderid>10000) o left

ZWOMILBSM0 l on L.tlntcode=t1.tlntcode join ZWOMEXPRM0 CP on T1.TLNTCODE=CP.T Lntcode where IsNull (T2.DELETEFG, ' 0 ') = ' 0 ' and I.mlbscode in (select value from #i) and i.locatype= '--and i.mlbs Type= ' and P.mlbscode in (select value from #p) and p.locatype= '--and p.mlbstype= ' + l.mlbscode in (select V Alue from #l) and l.locatype= ""--and l.mlbstype= ' and cp.companyn like '% ' [emailprotected]+ '% ' and CP. Sequence=0 ' EXEC sp_executesql @

.merchant_id=m.id) left join acquirer A on t_.acquirer_id = a.id) LEFT join acq_merchant am on t_.acq_merchant_id = am.id) LEFT JOIN Agency AG in m.agency_id = ag.id ORDER BY t.id desc where ID >0 limit 20;View mode:Local can be updated as long as the conditions of this view are satisfied;Cascaded must meet all of the view's criteria for the view to be updatedCRE

The system requires SQL optimization to optimize for less efficient SQL, making it more efficient to run, which requires a partial in/not in SQL to be modified to Exists/not existsHere's how to modify it:In SQL statementSELECT ID, category_id, htmlfile, title, CONVERT (varch