Hi,
I am not sure if I understand this.
And I am not aware of such change.
I tried reproducing this with 2.8 and it seems that `null` values are not
excluded from UDF results.
Here's what I tried:
var functions = require("org/arangodb/aql/functions");
/* register a simple UDF that returns null for any falsey value */
functions.register("foo::bar", function(a) { if (a) return a; return null;
});
db._query("FOR i IN [-1, 0, null, 1, 2] RETURN foo::bar(i)").toArray()
[
-1,
null,
null,
1,
2
]
To me it looks like that null return values from a UDF are included in
query results.
This doesn't change when I modify the UDF to return an array that includes
null values:
functions.register("foo::bar", function(a) { if (a) return [1, a]; return
[1, null]; });
db._query("FOR i IN [-1, 0, null, 1, 2] RETURN foo::bar(i)").toArray()
[
[
1,
-1
],
[
1,
null
],
[
1,
null
],
[
1,
1
],
[
1,
2
]
]
Still null values are included in the UDF result.
I tried the above with 2.8.11.
If the behavior is the same in later versions, then I think the behavior
hasn't changed.
However, if you are referring to JavaScript `undefined` values:
when a UDF returns `undefined`, any such value is converted to `null`,
because `undefined` has no equivalent in JSON.
But I neither think this behavior has changed between 2.8 and 3.x.
Can you supply an example query (and the UDF) that changed their behavior?
Thanks
Jan
Am Montag, 13. März 2017 08:48:13 UTC+1 schrieb Georgios Kafataridis:
>
> I noticed in arangodb 3 that when a UDF returns null as a result it is
> included in the resulting dataset.
> That created problems in parts of my code where I had pagination, because
> the results where void of any actual data but still included.
>
> In arango 2.8 null returns where excluded/ignored completely with no need
> to handle them in the query.
>
> I managed to resolve it easily by adding a filter excluding the null
> results but I wanted to ask though what drove you to this change. Is there
> any reference in the change log ?
>
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