redis/2

Availability::- use_module(library(redis)).(can be autoloaded)

[semidet]redis(+Connection, +Request)

This predicate is overloaded to handle two types of requests. First, it is a shorthand for redis(Connection, Command, _) and second, it can be used to exploit Redis pipelines and transactions. The second form is acticated if Request is a list. In that case, each element of the list is either a term Command -> Reply or a simple Command. Semantically this represents a sequence of redis/3 and redis/2 calls. It differs in the following aspects:

All commands are sent in one batch, after which all replies are read. This reduces the number of round trips and typically greatly improves performance.
If the first command is multi and the last exec, the commands are executed as a Redis transaction, i.e., they are executed atomically.
If one of the commands returns an error, the subsequent commands are still executed.
You can not use variables from commands earlier in the list for commands later in the list as a result of the above execution order.

Procedurally, the process takes the following steps:

Send all commands
Read all replies and push messages
Handle all callbacks from push messages
Check whether one of the replies is an error. If so, raise this error (subsequent errors are lost)
Bind all replies for the Command -> Reply terms.

Examples

?- redis(default,
         [ lpush(li,1),
           lpush(li,2),
           lrange(li,0,-1) -> List
         ]).
List = ["2", "1"].