Redis Lists: LPUSHX

Redis LPUSHX Command

Redis LPUSHX command is used to insert value at the head of the list stored at key, only if a key already exists and holds a list.

Here are some common uses and scenarios for the "LPUSHX" command:

• Conditional Prepending: Add elements to the beginning of a list only if the list is already present.
• Queue Management: Ensure elements are added to active queues without creating new ones.
• Task Prioritization: Insert high-priority tasks at the front of an existing task list.
• Event Handling: Add events to the start of an existing event list for immediate processing.
• Data Integrity: Prevent the accidental creation of lists when trying to prepend elements.

Syntax:

LPUSHX KEY_NAME VALUE1.. VALUEN     

Available since

2.2.0.

Return Value

Integer replies the length of the list after the push operations.

Return Value Type

Integer

Example: Redis LPUSHX

127.0.0.1:6379> LPUSH mycolor1 white
(integer) 1
127.0.0.1:6379> LPUSHX mycolor1 black
(integer) 2
127.0.0.1:6379> LPUSHX mycolor1 red
(integer) 3
127.0.0.1:6379> LPUSHX mycolor2 blue
(integer) 0

The key mycolor2 not exists, so return 0

127.0.0.1:6379> EXISTS mycolor2
(integer) 0
127.0.0.1:6379> LRANGE mycolor1 0 -1
1) "red"
2) "black"
3) "white"

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