partitioning

问题 Is there any way to get the number of elements in a spark RDD partition, given the partition ID? Without scanning the entire partition. Something like this: Rdd.partitions().get(index).size() Except I don't see such an API for spark. Any ideas? workarounds? Thanks 回答1: The following gives you a new RDD with elements that are the sizes of each partition: rdd.mapPartitions(iter => Array(iter.size).iterator, true) 回答2: PySpark: num_partitions = 20000 a = sc.parallelize(range(int(1e6)), num

问题 My question is triggered by the use case of calculating the differences between consecutive rows in a spark dataframe. For example, I have: >>> df.show() +-----+----------+ |index| col1| +-----+----------+ | 0.0|0.58734024| | 1.0|0.67304325| | 2.0|0.85154736| | 3.0| 0.5449719| +-----+----------+ If I choose to calculate these using "Window" functions, then I can do that like so: >>> winSpec = Window.partitionBy(df.index >= 0).orderBy(df.index.asc()) >>> import pyspark.sql.functions as f >>>

问题 I have 2 MySQL tables with the following schemas for a web site that's kinda like a magazine. Article (articleId int auto increment , title varchar(100), titleHash guid -- a hash of the title articleText varchar(4000) userId int) User (userId int autoincrement userName varchar(30) email etc...) The most important query is; select title,articleText,userName,email from Article inner join user on article.userId = user.UserId where titleHash = <some hash> I am thinking of using the articleId and

问题 I have a table partitioned using inherit in multiple tables for days. There is one insert trigger to insert the data to the proper table, so in theory the avl table shouldnt have any data CREATE OR REPLACE FUNCTION avl_db.avl_insert_trigger() RETURNS trigger AS $BODY$ BEGIN IF ( NEW.event_time >= '2017-06-01 00:00:00' AND NEW.event_time < '2017-06-02 00:00:00' ) THEN INSERT INTO avl_db.avl_20170601 VALUES (NEW.*); ELSEIF ( NEW.event_time >= '2017-06-02 00:00:00' AND NEW.event_time < '2017-06

问题 I have a graph G=(V,E) that both edges and nodes have weights. I want to partition this graph to create equal sized partitions. The definition of the size of partition is sum(vi)-sum(ej) where vi is a node inside that partition and ej is an edge between two nodes in that partition. In my problem the graph is very dense (almost complete). Is there any approximation algorithm for that? This is somehow similar to the problem in bin packing with overlapping objects where bins have the same size.

问题 Col1;Col2;Col3 12345;01;Y 12345;02;Y 12345;03;Y 22222;01;Y 22222;02;Y 22222;03;N 33333;01;N 44444;01;Y Need help in writing a SQL query to find all the records with value = 'Y' based on col1.For Eg output select Col1 should give the output as 12345 and 44444 [ not 22222 and 33333 as the col3 contains 'N' for them ] Thanks a lot for your time 回答1: I guess you need col1 where all values of col3 should be Y select col1 from demo group by col1 having count(*) = sum(Col3 = 'Y') Demo Or if there

问题 DROP TABLE temp; CREATE TABLE `temp` ( `CallID` bigint(8) unsigned NOT NULL, `InfoID` bigint(8) unsigned NOT NULL, `CallStartTime` datetime NOT NULL, `PartitionID` int(4) unsigned NOT NULL, KEY `CallStartTime`(`CallStartTime`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 PARTITION BY HASH (PartitionID) PARTITIONS 366 I use EXPLAIN in a sample query I get the next result: EXPLAIN PARTITIONS SELECT * FROM temp where PartitionID = 1 or EXPLAIN PARTITIONS SELECT * FROM temp where PartitionID =

问题 In Kotlin I can: val (specificMembers, regularMembers) = members.partition {it is SpecificMember} However to my knowledge I can not do something like: val (specificMembers as List<SpecificMember>, regularMembers) = members.partition {it is SpecificMember} My question would be - is there's an idiomatic way to partition iterable by class and typecast it those partitioned parts if needed. 回答1: The partition function will return a Pair<List<T>, List<T>> with T being the generic type of your

问题 In Kotlin I can: val (specificMembers, regularMembers) = members.partition {it is SpecificMember} However to my knowledge I can not do something like: val (specificMembers as List<SpecificMember>, regularMembers) = members.partition {it is SpecificMember} My question would be - is there's an idiomatic way to partition iterable by class and typecast it those partitioned parts if needed. 回答1: The partition function will return a Pair<List<T>, List<T>> with T being the generic type of your

问题 I want to partition a very large table. As the business is growing, partitioning by date isn't really that good because each year the partitions get bigger and bigger. What I'd really like is a partition for every 10 million records. The Mysql manual show this simple example: CREATE TABLE employees ( id INT NOT NULL, fname VARCHAR(30), lname VARCHAR(30), hired DATE NOT NULL DEFAULT '1970-01-01', separated DATE NOT NULL DEFAULT '9999-12-31', job_code INT NOT NULL, store_id INT NOT NULL )