Updated release docs
Project: http://git-wip-us.apache.org/repos/asf/tinkerpop/repo Commit: http://git-wip-us.apache.org/repos/asf/tinkerpop/commit/7149f8e8 Tree: http://git-wip-us.apache.org/repos/asf/tinkerpop/tree/7149f8e8 Diff: http://git-wip-us.apache.org/repos/asf/tinkerpop/diff/7149f8e8 Branch: refs/heads/master Commit: 7149f8e8c1c255420b19748632ee4d928480f2e2 Parents: 3201442 Author: Daniel Kuppitz <daniel_kupp...@hotmail.com> Authored: Fri Mar 2 14:04:58 2018 -0700 Committer: Daniel Kuppitz <daniel_kupp...@hotmail.com> Committed: Fri Mar 2 14:04:58 2018 -0700 ---------------------------------------------------------------------- docs/src/upgrade/release-3.4.x.asciidoc | 42 ++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/tinkerpop/blob/7149f8e8/docs/src/upgrade/release-3.4.x.asciidoc ---------------------------------------------------------------------- diff --git a/docs/src/upgrade/release-3.4.x.asciidoc b/docs/src/upgrade/release-3.4.x.asciidoc index ff7b458..5a355fa 100644 --- a/docs/src/upgrade/release-3.4.x.asciidoc +++ b/docs/src/upgrade/release-3.4.x.asciidoc @@ -28,3 +28,45 @@ NEED AN IMAGE Please see the link:https://github.com/apache/tinkerpop/blob/3.4.0/CHANGELOG.asciidoc#release-3-4-0[changelog] for a complete list of all the modifications that are part of this release. === Upgrading for Users + +==== Modifications to reducing barrier steps + +The behavior of `min()`, `max()`, `mean()` and `sum()` has been modified to return no result if there's no input. Previously these steps yielded the internal seed value: + +[source,groovy] +---- +gremlin> g.V().values('foo').min() +==>NaN +gremlin> g.V().values('foo').max() +==>NaN +gremlin> g.V().values('foo').mean() +==>NaN +gremlin> g.V().values('foo').sum() +==>0 +---- + +These traversals will no longer emit a result. Note, that this also affects more complex scenarios, e.g. if these steps are used in `by()` modulators: + +[source,groovy] +---- +gremlin> g.V().group(). +......1> by(label). +......2> by(outE().values("weight").sum()) +==>[software:0,person:3.5] +---- + +Since software vertices have no outgoing edges and thus no weight values to sum, `software` will no longer show up in the result. In order to get the same result as before, one would +have to add a `coalesce()`-step: + +[source,groovy] +---- +gremlin> g.V().group(). +......1> by(label). +......2> by(outE().values("weight").sum()) +==>[person:3.5] +gremlin> +gremlin> g.V().group(). +......1> by(label). +......2> by(coalesce(outE().values("weight"), constant(0)).sum()) +==>[software:0,person:3.5] +----
