Tuesday 10 January 2017

Redis PHP Interview questions and answers

Redis php interview questions and answers

Question: What is Redis?
Redis is an advanced key-value data store and cache. It has is also referred to as a data structure server as such the keys not only contains strings, but also hashes, sets, lists.

Question: What are the advantages of using Redis?
  1. It provides high speed
  2. It has got command level Atomic Operation (tx operation)
  3. It supports a server-side locking
  4. It has got lots of client lib

Question: What are the limitations of Redis?
  1. It is single threaded
  2. It has got limited client support
  3. It is not deployed

Question: Why Redis is different as compared to other key-value stores?
  1. Redis values can contain more complex data types, with atomic operations.
  2. Redis is an in-memory but persistent on disk database.

Question: How to delete current database?
redis-cli flushdb

Question: How to remove all database?
redis-cli flushall

Question: How to check redis is running?
try {
    $redis = new Redis();
    $redis->connect('', 6379);
    echo "Redis is running.";
    echo "Server is running: " . $redis->ping();
} catch (Exception $e) {
    echo $e->getMessage();

Question: How to set value in redis?
$redis->set("name", "Set string in redis");

Question: How to get value from redis?
 echo $redis->get('name'); //Set string in redis

Question: How to set multiple values (Array) in redis?
$redis->lpush("tutorials", "PHP");
$redis->lpush("tutorials", "MySQL");
$redis->lpush("tutorials", "Redis");
$redis->lpush("tutorials", "Mongodb");
$redis->lpush("tutorials", "Mysql");

Question: How to get array data from redis?
$list = $redis->lrange("tutorials", 0 ,5);   
/*Array ( [0] => Mysql [1] => Mongodb [2] => Redis [3] => MySQL [4] => PHP [5] => Mysql ) */
Question: How to get all keys from redis?
$keyList = $redis->keys("*");
/*Array ( [0] => tutorials [1] => name ) */
Question: How to stop redis?
/etc/init.d/redis-server stop

Question: How to start redis?
/etc/init.d/redis-server start

Question: How to re-start redis?
/etc/init.d/redis-server restart

Question: How do I move a redis database from one server to another?
  1. use BGSAVE command to Save a spanshot of the database into a dump.rdb
  2. Copy this dump.rdb file into another server.