MapReduce

问题 I am trying to figure out the different versions of hadoop and I got confusing after reading this page. Download 1.2.X - current stable version, 1.2 release 2.2.X - current stable 2.x version 2.3.X - current 2.x version 0.23.X - similar to 2.X.X but missing NN HA. Releases may be downloaded from Apache mirrors. Question: I think any release starting with 0.xx means it is a alpha version and should be not used in product, is that the case? What is the difference between 0.23.X and 2.3.X? it

问题 I have the following mongodb structure { "_id": ObjectId("507c80a143188f9610000003"), "date": ISODate("2012-10-15T21: 31: 13.0Z"), "uid": NumberInt(35920), "comp": NumberInt(770), "fields": { "rating": { "parent": "rating", "weight": NumberInt(2), "rel_weight": 0.11, }, "capacity": { "parent": "capacity", "weight": NumberInt(4), "rel_weight": 0.89, }, } } The "fields" attribute has 2 fields "rating" and "capacity" in it. But, each entry might have a different set of fields. eg. dimension,

问题 I am trying to use test CombineFileInputFormat to process few small files (20 files) of 8 MB each. I followed the sample given in this blog. I am able to implement and test it. The end result is correct. But what is surprising to me is that it is always ending up with only one map. I tried setting the attribute "mapred.max.split.size" various values like 16MB, 32MB etc (Of course in bytes) without any success. Is there anything else I need to do or is it the right behavior? I am running a two

问题 Hi I am new to MapReduce and HBase. Please guide. I am moving tabular data to HBase using MapReduce. Now data is reached in HBase (so in HDFS). I have created mapreduce job which will read tabular data from file and put it into Hbase using HBase APIs. Now my doubt is can I query HBase data using MapReduce? I dont want to execute HBase commands to query data. Is is possible to query data of HBase using MapReduce? Please help or advice. 回答1: Of course you can, HBase comes with a

问题 Given a large file containing data of the form, (V1,V2,...,VN) 2,5 2,8,9 2,5,8 ... I am trying to achieve a list of pairs similar to the following using Spark ((2,5),2) ((2,8),2) ((2,9),1) ((8,9),1) ((5,8),1) I tried the suggestions mentioned in response to an older question, but I have encountered some issues. For example, val dataRead = sc.textFile(inputFile) val itemCounts = dataRead .flatMap(line => line.split(",")) .map(item => (item, 1)) .reduceByKey((a, b) => a + b) .cache() val nums =

问题 i've searched for two days for a solution. but nothing worked. First, i'm new to the whole hadoop/yarn/hdfs topic and want to configure a small cluster. the message above doesn't show up everytime i run an example from the mapreduce-examples.jar sometimes teragen works, sometimes not. in some cases the whole job failed, in others the job finishes successfully. sometimes the job failes, without printing the message above. 14/06/08 15:42:46 INFO ipc.Client: Retrying connect to server: FQDN

问题 I was wondering whether its possible to pass values to a map function in couchDB design document. For Example: In the code below is it possible to pass a value that has been entered by the user and use that value to run the map function. Maybe I can pass users UserName when they login and then display the view based on the map function. function(doc) { if(doc.name == data-Entered-By-User) { emit(doc.type, doc); } } Thank you in advance. Regards 回答1: This is a common mistake in CouchDB when

问题 I am running a python MapReduce script on top of Amazons EMR Hadoop implementation. As a result from the main scripts, I get item item similiarities. In an aftercare step, I want to split this output into a seperate S3 bucket for each item, so each item-bucket contains a list of items similiar to it. To achieve this, I want to use Amazons boto python library in the reduce function of the aftercare step. How do I import external (python) libraries into hadoop, so that they can be used in a

问题 I have a Hive external table with parquet data. When I run select count(*) from table1 , it fails with Tez. But when execution engine is changed to MR it works. Any idea why it's failing with Tez? I'm getting the following error with Tez: Error: org.apache.hive.service.cli.HiveSQLException: Error while processing statement: FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.tez.TezTask at org.apache.hive.service.cli.operation.Operation.toSQLException(Operation.java:380

问题 From previous work on CouchDB 1.6.1, I know that it's possible to implement document joins in a couple ways: For example, with a simple schema of 'students and 'courses : // Students table | Student ID | Student Name | XYZ1 | Zach // Courses table | Course ID | Student ID | COURSE1 | XYZ1 This SQL query: SELECT [Student Name], [Course ID] FROM Students RIGHT OUTER JOIN Courses ON Students.[Student ID] = Courses.[Student ID] Could be implemented in CouchDB 1.6 with a map function: // Map