spark sql join optimization

Use connection (join) instead of subquery (sub-queries)MySQL supports SQL subquery starting from 4.1. This technique can use the SELECT statement to create a single-column query result, and then use the result as a filter for another query. For example, if we want to delete a customer who does not have any orders in the customer's basic information table, we can take advantage of the subquery to remove all

Tags: spark catalyst SQL Spark SQL sharkAfter an article on spark SQL Catalyst Source Code Analysis Physical plan, this article will introduce the specifics of the implementation of the physical plan Tordd:We all know a

Mysql: 21 best practices for performance optimization 5 [use and index equivalent columns when joining a table] bitsCN.com When you Join a table, use a column of equivalent type and index it. If your application has many JOIN queries, you should confirm that the Join fields in the two tables are indexed. In this way,

, especially Impala and the old version of Spark SQL, do not differentiate between binary data and string data when writing to the Parquet schema. This flag tells spark SQL to interpret the binary data as a string to provide compatibility. Spark.sql.parquet.int96AsTimestamp True Some systems tha

Label:Reference article: SQL Server Performance Tuning Overview (good summary, don't miss it.)Database: System Database Usage of subqueries A subquery is a select query that is nested within a SELECT, INSERT, UPDATE, DELETE statement, or other subquery. Subqueries can be used anywhere that an expression is allowed to be used. Subqueries can make our programming flexible and can be used to implement some special functions. But in performance, often an

the future versionsupport for other clustersManager. finally, Spark1.2added a pair ofScala's2.11Support. aboutScala2.11for an introduction, seeIntroductiondocumentation. Spark StreamingThis release includes Spark streaming Library two mainfunctionSupplement,a pythonAPI, a writeLogbeforeto befull h/a driver. Python'sAPIcovers almost allof theDSTREAMConversions andOutput Operation. currently supportsbased

SQL Optimization-logical Optimization-database constraint rules and semantics optimization, SQL Semantics 1) database integrity ① Entity Integrity (Entity Integrity): yourself A) a link corresponds to an entity set in the real world. -- ER Model B) Entities i

Dataframe more information about the structure of the data. is the schema.The RDD is a collection of distributed Java objects. Dataframe is a collection of distributed row objects.DataFrame provides detailed structural information that allows Sparksql to know clearly what columns are contained in the dataset, and what are the names and types of the columns?The RDD is a collection of distributed Java objects. Dataframe is a collection of distributed row objects. Dataframe In addition to providing

Tags: Specify ext ORC process ERP conf def IMG ArtSparksql data sources: creating dataframe from a variety of data sources Because the spark sql,dataframe,datasets are all shared with the Spark SQL Library, all three share the same code optimization, generation, and executio

Mysql Database SQL Optimization-subquery optimization and mysql Database SQL Optimization1. What are subqueries and table join queries:Subquery: The select statement is used in the select or where clause of the primary SQL stateme

Tags: mysqlI'm having a SQL problem with the code today:To query the ID of a table, match the ID of Table B and query all the contents of Table B:Before optimization:mysql[xxuer]>select ->count (*) ->from ->t_cmdb_app_ Version ->where ->id IN (select -> pid -> From -> t_cmdb_app_relationUNIONSELECT -> rp_id -> from -> nbsP;t_cmdb_app_relation); +----------+ |count (*) | +----------+ |266| +----------+ 1rowinset (0.21sec)After optimization:mysql[xxuer]

Tags: mysq target ima STR Force Avoid association table WWW StatusProblemThe "show full processlist" statement makes it easy to find the problem SQL, as follows: SELECT post.* from post INNER JOIN post_tag on post.id = post_tag.post_id WHERE post.status = 1 and post_tag.t ag_id = 123 ORDER by post.created DESC LIMIT 100 Note: Because post and tag are many-to-many relationships, there is an association table

times times smaller, here is the experience)3. Large table to large table (Sort Merge Join)The two tables were re-shuffle by the join keys to ensure that records with the same join keys value were divided into the corresponding partitions. After partitioning, the data within each partition is sorted, sorted, and then connected to the records in the corresponding

Label:Error Description:SQL three tables do join run error; The following error is performed with hive: Diagnostic Messages for this Task:Container [pid=27756,containerid=container_1460459369308_5864_01_000570] is running beyond physical memory limits. Current usage:4.2 GB of 4 GB physical memory used; 5.0 GB of 16.8 GB virtual memory used. Killing container.Container killed on request. Exit Code is 143Container exited with a Non-zero exit c

1. SQL in Oracle Select Count(1) fromA_v_pwyzl_custacct_psmis Twhere not exists(Select1 fromTb_show_multi_question QWHEREQ.dqmp_rule_code =' compare to System only ' andq.dqmp_role_id =' 105754659 ' andq.dqmp_target_id = T.dqmp_mrid) and not EXISTS(Select/*+Index(s) */1 fromA_v_pwyzl_custacct_gis swhereS.DQMP_CPK = T.DQMP_CPK) andT.is_repeat =' 0 '; 2. Hive/shark version Select Count(1) from(Selectt.*,q.dqmp_quest

SQL Optimization-logical Optimization-external connections, nested connections, and elimination of connections, SQL nesting 1) eliminate external connections ① External connection Introduction 1) left join/left outer join:

I. Basic CONCEPTSAbout the JOIN keyword in SQL statements, which is a more common and less understandable keyword, the following example gives a simple explanation – build table User1,user2:Table1:create table user2 (id int, user_name varchar, over varchar (10));Insert into User1 values (1, ' Tangseng ', ' DTGDF ');Insert into User1 values (2, ' Sunwukong ', ' dzsf ');Insert into User1 values (1, ' Zhubajie

4 four Iii. SQL server processes the logical sequence of connections: The query engine selects the most effective method from a variety of feasible methods to process connections. The actual execution process of various connections uses a variety of optimization methods, but the logic order is: Application fromClause. Application whereThe join condition and Sear

The previous articles explained the core execution process of spark SQL and the SQL parser of the Catalyst Framework for Spark SQL to accept user input SQL, parsed to generate unresolved Logical plan. We remember another core comp

To put it simply, Shark's next-generation technology is spark SQL.Because Shark is dependent on hive, the advantage of this architecture is that traditional Hive users can seamlessly integrate Shark into existing systems to run query load.But there are some problems: on the one hand, with the version upgrade, the query optimizer relies on Hive, inconvenient to add new optimization strategy, need to do anoth