The cayley repl command #

The REPL is the acronym of Read-Eval-Print-Loop. We can use the cayley repl command to open a console to an existing database, and interactively execute queries and other operations on the database.

The console works similar to a normal Linux console. We can type in the expressions, then press the Enter, and the interpreter will execute, then prints the results. It is also possible to use the up/down arrows to navigate among the previously entered commands. The expressions we execute will be stored into a .cayley_history file, that we can open with a text editor, and extract the expressions we used previously. This way the REPL is a very efficient tool to experiment with queries, then move the results of experiments to the final query files.

The following session starts REPL on an existing database, then queries and prints all the nodes stored in the database:

    $ cayley repl --db bolt --dbpath /home/tombenke/tmp/cayley/ 
    I0915 18:02:08.623789   25897 cayley.go:63] Cayley version: 0.7.5 (cf576babb7db)
    I0915 18:02:08.623971   25897 database.go:187] using backend "bolt" (/home/tombenke/tmp/cayley/)
    cayley> g.V().All()

    ****
    id : <bob>
    ****
    id : <status>
    ****
    id : cool_person
    ****
    id : <alice>
    ****
    id : <greg>
    ****
    id : <emily>
    ****
    id : <smart_graph>
    ****
    id : <predicates>
    ****
    id : <dani>
    ****
    id : <fred>
    ****
    id : smart_person
    ****
    id : <charlie>
    ****
    id : <are>
    ****
    id : <follows>
    -----------
    14 Results
    Elapsed time: 3.046727 ms

    cayley>

Let’s see the content of the .cayley_history file after the session:

    $ cat .cayley_history 
    
    g.V().All()

The Discover and unknown graph section demonstrates how can we use the cayley repl command to discover a graph we know nothing about.