apoc.custom and Cypher versions

[mnd999]

How will the apoc.custom functions and procedures handle Cypher versions? Does procedure retain the Cypher version it was defined against, or should it always evaluate using the version context it is being called from.

If it's the former, then what happens when the Cypher version used to define the procedure is deprecated and removed? If it's the latter, the procedure or function could have different behaviour depending on the call context.

[jexp]

Great question.

I guess until you explicitely specify a cypher version in the inner query it will inherit it from the running context
as it uses transaction.executeCypher() which I think? is bound to the currently running version

I think when the next cypher version is removed apoc.custom will be removed as well because we will have cypher-defined functions in the language :)

[vga91]

It seems that it always keeps the version specified in the inner query (or the default version), regardless of whether it is recorded or called with a different cypher version.

We can check it here
by debugging or adding e.g. a System.out.println("cypher version = " + result.getExecutionPlanDescription().getArguments().get("version"));.

These are the results I get:

CALL apoc.custom.installProcedure('answer2() :: (answer::INT)','RETURN 42 as answer')
CALL custom.answer2()
// print: cypher version = 5

CYPHER 25 CALL custom.answer2()
// print: cypher version = 5

CYPHER 25 CALL apoc.custom.installProcedure('answer3() :: (answer::INT)','RETURN 42 as answer')
CYPHER 25 CALL custom.answer3()
// print: cypher version = 5

CYPHER 5 CALL apoc.custom.installProcedure('answer4() :: (answer::INT)','CYPHER 25 RETURN 42 as answer')
CALL custom.answer4()
// print: cypher version = 25

CALL apoc.custom.installProcedure('answer5() :: (answer::INT)','CYPHER 25 RETURN 42 as answer')
CYPHER 5 CALL custom.answer5()
// print: cypher version = 25

CYPHER 5 CALL apoc.custom.installProcedure('answer6() :: (answer::INT)','CYPHER 5 RETURN 42 as answer')
CALL custom.answer6()
// print: cypher version = 5

CYPHER 25 CALL custom.answer6()
// print: cypher version = 5

As mentioned, this should not be a problem in the future, as they should be removed.