How to Work on Redis Instances and Keys?

In single Redis instance, there are 16 databases by default. These databases are identified/denoted by a number and not by name and these numbers are called index numbers. Though you can always increase the number of databases. We have covered this at last leg of the tutorial.

• Check Number of Databases in your current Redis instance configuration
  CONFIG GET databases
  Here 16 is the number of databases
  
  
• Check the number of databases set in Redis .conf file
  The path to .conf file /etc/redis/redis.conf
  
  
• Check Number of keys and databases holding data
  INFO keyspace
  db0 is database and 0 is index number for the particular database
  db0 has 8 keys inside it.
  
  
• List all keys in database db0
  key *
  1-8 are total 8 keys in db0 that we checked on last 
  
  
• Check key type
  type <key>
  Here <key> is name i.e. series of numbers
  In the output you will get the type of key. For us its hash
  
  for “string“: get <key>
  for “hash“: hgetall <key>
  for “lrange <key> 0 -1
  for “set“: smembers <key>
  for “zset“: zrange <key> 0 -1 withscores
• Check the content of key type hash
  hgetall <key>
  
  
• Check the content of key type <strong">string
  
  
• Change the current database to db1
  select <db_id>
  Prompt will show db_id within square brackets
  
  
  Check if the database can be switched outside the configuration range
  Our instance has total 16 Databases with the index from 0-15. Here we will try switching to Database with index number 16 which means the 17th database
  select 16
  
  
• Change the current database and add some keys and delete them later
  Change the working database
  select 15
  
  Check Number of keys and databases holding data
  INFO keyspace
  
  Save key ‘anything’ with value abc
  
  Check Number of keys and databases holding data
  INFO keyspace
  Here in db15, there is one key added
  
  Save key ‘hello’ with value world
  
  Check Number of keys and databases holding data
  INFO keyspace
  Here in db15 there is one more key is added and total keys now are two
  
  Remove key ‘hello‘ and check keyspace
  Total one key is left in db15
  
  Remove key ‘anything‘ and check keyspace
  No keys left ins db15
  
  
• Increase Number of databases from 16 as default to 40 or your choice.
  Check current databases.
  CONFIG GET databases
  Here 16 is the number of databases
  
  Edit Redis .conf file located at /etc/redis/redis.conf
  Search for ‘Set the number of databases’
  16 here can differ with any number.
  We will change 16 to 40 and restart redis server.
  
  Run the following command to shutdown redis-server
  redis-cli shutdown
  Start redis-server using your configuration file.
  redis-server /etc/redis/redis.conf
  Check current databases.
  CONFIG GET databases
  Here 40 is number of databases which means index number 0-39