1 reply

Is the first traversal pattern evaluated by Match well defined

Hi,

It seems to me that if the match step is able to dynamically select the first traversal pattern (as it does all other traversal patterns), and this selection isn't the same across all traversers, the behaviour of match isn't well defined.

Consider the simple graph

(a) -> (b) -> (c)

(a) -> (b) -> (c)

Suppose we have some match statement with two patterns that both capture endpoint vertices x and y, such that the patterns both match x=a, y=c and x=c, y=a.

V().match( 
as("x").identity().
as("x1").both().both().as("y1").
simplePath().from("x1").to("y1").
as("y"),
as("x").identity().
as("x2").both().both().as("y2").
simplePath().from("x2").to("y2").
as("y")
).
select("start","x","y");

V().match( 
as("x").identity().
as("x1").both().both().as("y1").
simplePath().from("x1").to("y1").
as("y"),
as("x").identity().
as("x2").both().both().as("y2").
simplePath().from("x2").to("y2").
as("y")
).
select("start","x","y");

Extremely long-winded but basically both patterns will move either two out or two in (acyclicly) and capture the endpoints.

If the traverser starting at vertex a evaluates the first pattern first, and the traverser starting at vertex b evaluates the second pattern first; they will both have the same result [(x=a, y=b)], instead of the expected behaviour [(x=a, y=b), (x=b, y=a)].

I'd imagine right now the first pattern is just evaluated, but I'm not entirely sure about if this is guaranteed for OLAP, and it's also not documented as far as I can tell.

Apache TinkerPop•2y ago•

1 reply

Neptunion

Is the first traversal pattern evaluated by Match well defined

(a) -> (b) -> (c)

(a) -> (b) -> (c)

Suppose we have some match statement with two patterns that both capture endpoint vertices x and y, such that the patterns both match x=a, y=c and x=c, y=a.

V().match( 
as("x").identity().
as("x1").both().both().as("y1").
simplePath().from("x1").to("y1").
as("y"),
as("x").identity().
as("x2").both().both().as("y2").
simplePath().from("x2").to("y2").
as("y")
).
select("start","x","y");

V().match( 
as("x").identity().
as("x1").both().both().as("y1").
simplePath().from("x1").to("y1").
as("y"),
as("x").identity().
as("x2").both().both().as("y2").
simplePath().from("x2").to("y2").
as("y")
).
select("start","x","y");

Is the first traversal pattern evaluated by Match well defined

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