Hbase Commands
1. Connect to HBase. $ hbase shell hbase(main):001:0> Display HBase Shell Help Text. Type help and press Enter, to display some basic usage information for […]
Database
Install Hbase 2.x with Hadoop 3.x
Hbase – Pseudo Distributed mode of installation: This is a method for Hbase Installation, known as Pseudo Distributed mode of Installation. Below are the steps […]
Install Hadoop 3.x: Single Node Hadoop Cluster
We are going to setup all the NameNode, DataNode, ResourceManager and NodeManager on a single machine. Step 1: Create user and group: groupadd hadoop useradd […]
Configure Redis Password
Configuring a Redis password enables one of its two built-in security feature – the auth command, which requires clients to authenticate to access the database. […]
How to Check Postgres Replication
Run the following command in Master Node: select application_name, state, sync_priority, sync_state from pg_stat_replication; You should see the below: application_name | state | sync_priority | […]
Postgres SQL, Conditions using CASE
The SQL CASE expression is a generic conditional expression, similar to if/else statements in other programming languages: CASE WHEN condition THEN result [WHEN …] [ELSE […]
Tuning Semaphore for Postgres
Edit the file sysctl.conf: vi /etc/sysctl.conf Add: kernel.sem = 250 512000 100 2048 For the settings to take effect, run: sysctl -p Tuning Semaphore will […]
Install and Setup Redis
Download and Untar Redis Installer # wget http://download.redis.io/releases/redis-2.8.3.tar.gz # tar -xzvf redis-2.8.3.tar.gz Install GCC & TCL (if not yet) # yum install gcc tcl Enter […]
Tracking Postgres Process and Current Executing SQL
In the database server, check the SQL processes: ps -aux | grep postgres This will list all postgres processes. Pick the PID of the problematic […]
MongoDB Common Commands
DATABASE COMMANDS: list databases: show dbs list Collections/Tables: show collections //output every collection OR show tables OR db.getCollectionNames() Select specific collection/table: db.collectionName.find() ROLES COMMANDS: list […]