Redis List

• Redis lists are implemented via Linked Lists.
• Accessing an element by index is very fast in lists implemented with an Array and not so fast in lists implemented by linked lists.

LPUSH RPUSH

http://redisdoc.com/list/lpush.html http://redisdoc.com/list/rpush.html

LPUSH key value [value …]

127.0.0.1:6379> lpush listA 1 2 3 4 5
(integer) 5
127.0.0.1:6379> lpush listA 5 4 3 2 1
(integer) 10
127.0.0.1:6379> lrange listA 0 -1
 1) "1"
 2) "2"
 3) "3"
 4) "4"
 5) "5"
 6) "5"
 7) "4"
 8) "3"
 9) "2"
10) "1"
127.0.0.1:6379> rpush listA a b c
(integer) 13
127.0.0.1:6379> lrange listA 0 -1
 1) "1"
 2) "2"
 3) "3"
 4) "4"
 5) "5"
 6) "5"
 7) "4"
 8) "3"
 9) "2"
10) "1"
11) "a"
12) "b"
13) "c"

LPUSHX key value

http://redisdoc.com/list/lpushx.html

和 LPUSH key value [value …] 命令相反, 當 key 不存在時, LPUSHX 命令什麼都不做

RPOP

http://redisdoc.com/list/rpop.html

RPOP key

127.0.0.1:6379> rpop listA
"c"

lrange listA 0 -1
 1) "1"
 2) "2"
 3) "3"
 4) "4"
 5) "5"
 6) "5"
 7) "4"
 8) "3"
 9) "2"
10) "1"
11) "a"
12) "b"

LTRIM

http://redisdoc.com/list/ltrim.html

LTRIM key start stop

127.0.0.1:6379> lpush alpha a b c d e f g
(integer) 7
127.0.0.1:6379> lrange alpha 0 -1
1) "g"
2) "f"
3) "e"
4) "d"
5) "c"
6) "b"
7) "a"
127.0.0.1:6379> ltrim alpha 0 5
OK
127.0.0.1:6379> lrange alpha 0 -1
1) "g"
2) "f"
3) "e"
4) "d"
5) "c"
6) "b"

LSET

http://redisdoc.com/list/lset.html

LSET key index value

127.0.0.1:6379> lrange alpha 0 -1
1) "g"
2) "f"
3) "e"
4) "d"
5) "c"
6) "b"
127.0.0.1:6379> lset alpha 0 kk
OK
127.0.0.1:6379> lrange alpha 0 -1
1) "kk"
2) "f"
3) "e"
4) "d"
5) "c"
6) "b"

LINDEX

http://redisdoc.com/list/lindex.html

LINDEX key index

127.0.0.1:6379> lrange alpha 0 -1
1) "kk"
2) "f"
3) "e"
4) "d"
5) "c"
6) "b"
127.0.0.1:6379> lindex alpha 3
"d"

LINSERT

http://redisdoc.com/list/linsert.html

LINSERT key BEFORE|AFTER pivot value

127.0.0.1:6379> lrange alpha 0 -1
1) "kk"
2) "f"
3) "e"
4) "d"
5) "c"
6) "b"
127.0.0.1:6379> linsert alpha before d yy
(integer) 7
127.0.0.1:6379> lrange alpha 0 -1
1) "kk"
2) "f"
3) "e"
4) "yy"
5) "d"
6) "c"
7) "b"

LREM

http://redisdoc.com/list/lrem.html

LREM key count value

count > 0：從表頭開始向表尾搜索，value取出的元素，數量為count。 count < 0: 從表尾開始向表頭搜索，value取出的元素，數量為count絕對值。 count = 0: 移除表中所有與value發現的值。

127.0.0.1:6379> lrange alpha 0 -1
1) "kk"
2) "f"
3) "e"
4) "yy"
5) "d"
6) "c"
7) "b"
127.0.0.1:6379> lrem alpha 1 yy
(integer) 1
127.0.0.1:6379> lrange alpha 0 -1
1) "kk"
2) "f"
3) "e"
4) "d"
5) "c"
6) "b"

127.0.0.1:6379> lpush alpha yy yy yy yy
(integer) 10
127.0.0.1:6379> lrange alpha 0 -1
 1) "yy"
 2) "yy"
 3) "yy"
 4) "yy"
 5) "kk"
 6) "f"
 7) "e"
 8) "d"
 9) "c"
10) "b"
127.0.0.1:6379> lrem alpha 2 yy
(integer) 2
127.0.0.1:6379> lrange alpha 0 -1
1) "yy"
2) "yy"
3) "kk"
4) "f"
5) "e"
6) "d"
7) "c"
8) "b"

Cheat Sheet

RPUSH mylist "hello" (Insert all the specified values at the tail of the list stored at key.)

LRANGE mylist 0 -1 (Returns the specified elements of the list stored at key.)

LPUSH mylist "world" (Insert all the specified values at the head of the list stored at key.)

RPUSHX mylist "World" (Inserts value at the tail of the list stored at key, only if key already exists and holds a list.)

LPUSHX mylist "World" (Inserts value at the head of the list stored at key, only if key already exists and holds a list.)

RPOP mylist (Removes and returns the last element of the list stored at key.)

LPOP mylist (Removes and returns the first element of the list stored at key.)

LTRIM mylist 1 -1 (Trim an existing list so that it will contain only the specified range of elements specified)

LSET mylist 0 "four" (Sets the list element at index to value.)

LINDEX mylist 0 (Returns the element at index in the list stored at key.)

LINSERT mylist BEFORE "World" "There" (Inserts value in the list stored at key either before or after the reference value pivot.)

LLEN mylist (Returns the length of the list stored at key. )

LREM mylist 2 "hello" (Removes the first count occurrences of elements equal to value from the list stored at key.)