This writing is actually a draft note made for myself, so that I myself don’t forget what I had learned. But I think this note will be helpful for those who want to learn Redis. If you don’t know what Redis is, or haven’t installed Redis in your system yet, check it out here.
1. Hello World in Redis
1.1. PING
Returns PONG if no argument is provided, otherwise return a copy of the argument as a bulk. This command is often used to test if a connection is still alive, or to measure latency.
Set key to hold the string value. If key already holds a value, it is overwritten, regardless of its type.
1.4. GET
Get the value of key. If the key does not exist the special value nil is returned. An error is returned if the value stored at key is not a string, because GET only handles string values.
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127.0.0.1:6379> SET foo 100
OK
127.0.0.1:6379> GET foo
"100"
127.0.0.1:6379> SET bar "Hello World!"
OK
127.0.0.1:6379> GET bar
"Hello World!"
127.0.0.1:6379> GET nonexisting
(nil)
1.5. INCR
Increments the number stored at key by one. If the key does not exist, it is set to 0 before performing the operation. An error is returned if the key contains a value of the wrong type or contains a string that can not be represented as integer. This operation is limited to 64 bit signed integers.
1.6. DECR
Decrements the number stored at key by one. If the key does not exist, it is set to 0 before performing the operation. An error is returned if the key contains a value of the wrong type or contains a string that can not be represented as integer. This operation is limited to 64 bit signed integers.
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127.0.0.1:6379> INCR foo
(integer) 101
127.0.0.1:6379> GET foo
"101"
127.0.0.1:6379> DECR foo
(integer) 100
127.0.0.1:6379> GET foo
"100"
1.7. EXISTS
Returns if key exists:
- 1 if the key exists.
- 0 if the key does not exist.
1.8. DEL
Removes the specified keys. A key is ignored if it does not exist.
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127.0.0.1:6379> EXISTS foo
(integer) 1
127.0.0.1:6379> EXISTS nosuchkey
(integer) 0
127.0.0.1:6379> EXISTS foo bar nosuchkey
(integer) 2
127.0.0.1:6379> DEL bar
(integer) 1
127.0.0.1:6379> EXISTS bar
(integer) 0
127.0.0.1:6379> GET bar
(nil)
1.9. FLUSHALL
Delete all the keys of all the existing databases, not just the currently selected one. This command never fails.
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127.0.0.1:6379> FLUSHALL
OK
127.0.0.1:6379> GET foo
(nil)
127.0.0.1:6379>
1.10. EXPIRE
Set a timeout on key. After the timeout has expired, the key will automatically be deleted. A key with an associated timeout is often said to be volatile in Redis terminology.
1.11. TTL
Returns the remaining time to live of a key that has a timeout. This introspection capability allows a Redis client to check how many seconds a given key will continue to be part of the dataset.
Set key to hold the string value and set key to timeout after a given number of seconds. This command is equivalent to executing the following commands:
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SET mykey value
EXPIRE mykey seconds
1.13. PERSIST
Remove the existing timeout on key, turning the key from volatile (a key with an expire set) to persistent (a key that will never expire as no timeout is associated).
Sets the given keys to their respective values. MSET replaces existing values with new values, just as regular SET. See MSETNX if you don’t want to overwrite existing values.
1.15. APPEND
If key already exists and is a string, this command appends the value at the end of the string. If key does not exist it is created and set as an empty string, so APPEND will be similar to SET in this special case.
1.16. RENAME
Renames key to newkey. It returns an error when key does not exist. If newkey already exists it is overwritten, when this happens RENAME executes an implicit DEL operation, so if the deleted key contains a very big value it may cause high latency even if RENAME itself is usually a constant-time operation.
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127.0.0.1:6379> MSET key1 "Hello" key2 "world"
OK
127.0.0.1:6379> GET key1
"Hello"
127.0.0.1:6379> GET key2
"world"
127.0.0.1:6379> APPEND key1 " world!"
(integer) 12
127.0.0.1:6379> GET key1
"Hello world!"
127.0.0.1:6379> RENAME key1 greeting
OK
127.0.0.1:6379> GET key1
(nil)
127.0.0.1:6379> GET greeting
"Hello world!"
Insert all the specified values at the head of the list stored at key. If key does not exist, it is created as empty list before performing the push operations.
2.1.2. LRANGE
Returns the specified elements of the list stored at key. The offsets start and stop are zero-based indexes, with 0 being the first element of the list (the head of the list), 1 being the next element and so on.
2.1.3. RPUSH
Insert all the specified values at the tail of the list stored at key. If key does not exist, it is created as empty list before performing the push operation.
127.0.0.1:6379> LPUSH people "arafat"
(integer) 1
127.0.0.1:6379> LPUSH people "Jen"
(integer) 2
127.0.0.1:6379> LPUSH people "Tom"
(integer) 3
127.0.0.1:6379> LRANGE people 0 -1
1) "Tom"
2) "Jen"
3) "arafat"
127.0.0.1:6379> LRANGE people 1 2
1) "Jen"
2) "arafat"
127.0.0.1:6379> RPUSH people "Harry"
(integer) 4
127.0.0.1:6379> LRANGE people 0 -1
1) "Tom"
2) "Jen"
3) "arafat"
4) "Harry"
2.1.4. LPOP
Removes and returns the first element of the list stored at key.
2.1.5. RPOP
Removes and returns the last element of the list stored at key.
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127.0.0.1:6379> LRANGE people 0 -1
1) "Tom"
2) "Jen"
3) "arafat"
127.0.0.1:6379> LPOP people
"Tom"
127.0.0.1:6379> LRANGE people 0 -1
1) "Jen"
2) "arafat"
3) "Harry"
127.0.0.1:6379> RPOP people
"Harry"
127.0.0.1:6379> LRANGE people 0 -1
1) "Jen"
2) "arafat"
2.1.6. LINSERT
Inserts element in the list stored at key either before or after the reference value pivot.
When key does not exist, it is considered an empty list and no operation is performed.
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127.0.0.1:6379> LRANGE people 0 -1
1) "Jen"
2) "arafat"
127.0.0.1:6379> LINSERT people BEFORE "arafat" "Tom"
(integer) 3
127.0.0.1:6379> LRANGE people 0 -1
1) "Jen"
2) "Tom"
3) "arafat"
2.2. Sets
2.2.1. SADD
Add the specified members to the set stored at key. Specified members that are already a member of this set are ignored. If key does not exist, a new set is created before adding the specified members.
2.2.2. SMEMBERS
Returns all the members of the set value stored at key.
2.2.3. SISMEMBER
Returns if member is a member of the set stored at key.
Returns the set cardinality (number of elements) of the set stored at key.
2.2.5. SMOVE
Move member from the set at source to the set at destination. This operation is atomic. In every given moment the element will appear to be a member of source or destination for other clients.
2.2.6. SREM
Remove the specified members from the set stored at key. Specified members that are not a member of this set are ignored. If key does not exist, it is treated as an empty set and this command returns 0.
Adds all the specified members with the specified scores to the sorted set stored at key. It is possible to specify multiple score / member pairs. If a specified member is already a member of the sorted set, the score is updated and the element reinserted at the right position to ensure the correct ordering.
2.3.2. ZRANK
Returns the rank of member in the sorted set stored at key, with the scores ordered from low to high. The rank (or index) is 0-based, which means that the member with the lowest score has rank 0.
2.3.3. ZRANGE
Returns the specified range of elements in the sorted set stored at key.
2.3.4. ZINCRBY
Increments the score of member in the sorted set stored at key by increment. If member does not exist in the sorted set, it is added with increment as its score (as if its previous score was 0.0). If key does not exist, a new sorted set with the specified member as its sole member is created.
Sets field in the hash stored at key to value. If key does not exist, a new key holding a hash is created. If field already exists in the hash, it is overwritten.
2.4.2. HGET
Returns the value associated with field in the hash stored at key.
2.4.3. HGETALL
Returns all fields and values of the hash stored at key. In the returned value, every field name is followed by its value, so the length of the reply is twice the size of the hash.
