A simple script to print the size of each your Redis databases. (Calculate size per Redis database)

redis_size_per_database.sh

#!/usr/bin/env bash

human_size() {
    awk -v sum="$1" ' BEGIN {hum[1024^3]="Gb"; hum[1024^2]="Mb"; hum[1024]="Kb"; for (x=1024^3; x>=1024; x/=1024) { if (sum>=x) { printf "%.2f %s\n",sum/x,hum[x]; break; } } if (sum<1024) print "<1kb"; } '
}

# change your connect settings (DSN)
# redis_cmd='redis-cli -h host -p 6379 -a pass'
redis_cmd='redis-cli'

for db in `$redis_cmd INFO keyspace | grep -Eo 'db[0-9]{1,4}' | grep -Eo '[0-9]{1,4}'`; do
    sum=0
    for k in `$redis_cmd -n $db  keys "*"`; do
        size=$($redis_cmd -n $db debug object $k | perl -wpe 's/^.+serializedlength:([\d]+).+$/$1/g')
        case $size in
            ''|*[!0-9]*) size=0 ;;
        esac
        sum=$(( $sum + $size))
    done;
    echo Database \#$db size `human_size $sum`
done