Running our first MapReduce job We will use the WordCount example job which reads text files and counts how often words occur. The input is text files and the output is text files, each line of which contains a word…
if you’re curious to know whether we’ve password option file concept in MongoDB something similar to MySQL (refer below links). http://dev.mysql.com/doc/refman/5.1/en/password-security-user.html http://stackoverflow.com/questions/16299603/mysql-utilities-my-cnf-option-file With this, we can actually save credentials in a option hidden file within client session and we no…
We usually did see some performance boost when NUMA was disabled using -> numactl –interleave=all ….. Below are the details from MongoDB http://docs.mongodb.org/manual/administration/production-notes/ Running MongoDB on a system with Non-Uniform Access Memory (NUMA) can cause a number of operational problems,…
Hive is a data warehouse that uses MapReduce to analyze data stored on HDFS. In particular, it provides a query language called HiveQL that closely resembles the common Structured Query Language (SQL) standard. Prerequisites Unlike Hadoop, there are no Hive…
–> To find documents in a collection we have syntax db.<collection Name>.find(); –> db.books.find(); — it will provide all documents in collection books. It actually returns a cursor. –> To make the output look a bit pretty we have following…
Map step: mapper.py It will read data from STDIN, split it into words and output a list of lines mapping words to their (intermediate) counts to STDOUT. The Map script will not compute an (intermediate) sum of a word’s occurrences…
DELETE WITH LIMIT helps when there are duplicate records in the DB and you want to keep only few records from them and wanted to delete the rest of all. LIMIT with DELETE Query :- mysql>…
One of the common error in MySQL Replication is ‘Duplicate Entry’ – Error 1062. This pop-ups only if there are any manual intervention. The SQL Thread stops with this error. Just check the record in the error on both master…
[root@my-host-name bin]$ cat /etc/mongod.conf # MongoDB Configuration File # # General Settings journal = true fork = true quiet = true directoryperdb = true smallfiles = true # Logging verbose = true logappend = true oplogSize = 50 #logpath =…
What is opLog ? Just as Transaction Log in MS SQL Server or Binary log in MySQL, all those transactions on MongoDB RS will be written into a separate file, called opLog. This opLog will have a fixed size, which…