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https://issues.apache.org/jira/browse/TINKERPOP-3274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18136927#comment-18136927
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ASF GitHub Bot commented on TINKERPOP-3274:
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xiazcy opened a new pull request, #3762:
URL: https://github.com/apache/tinkerpop/pull/3762
https://issues.apache.org/jira/browse/TINKERPOP-3274
Adds `T.labels`, the token-level counterpart of the `labels()` step and
`Element.labels()`. It works with an element's full label set as a
`Set<String>`.
### Changes
- `T.labels` is accepted by `by()`, `has()`, the Gremlin grammar and all
GLVs, and as a map key.
- On creation, `addV()`, `mergeV()` and `graph.addVertex()` accept
`T.labels` as a synonym for `T.label`.
- `addE()` and `mergeE()` also accept `T.labels`, with at most one label,
because an edge always has exactly one label. An empty set is treated as an
omitted label, and a set with more than one label raises an error.
- A label in `mergeE()` `option(onMatch)` now raises an error, because an
existing edge's label cannot change.
- Under `with("multilabel")`, `elementMap()` and `valueMap()` key the label
set under `T.labels` instead of `T.label`.
- `addV()` given an empty label set now creates a label-less vertex on a
`ZERO_OR_MORE` graph, matching `graph.addVertex()`.
- New `HasContainer.isLabelKey()` recognizes both `~label` and `~labels`
filters. `InlineFilterStrategy` now uses it.
### Compatibility
- `T.labels` is declared last in the `T` enum, so the Gryo ordinals of the
existing tokens are unchanged.
- Older servers and drivers can't deserialize `T.labels`, so traffic that
uses it needs 4.x on both ends.
- Gremlin Server now reserves `labels`, `~labels` and `~LABELS` as parameter
names for `gremlin-groovy` requests.
- Code that read the label set from `T.label` in `multilabel` output must
read `T.labels` instead.
- Providers that detect label filters by key should use `isLabelKey()`.
Otherwise they skip their label index for `has(T.labels, ...)` and fall back to
a scan; results are still correct.
### Known issue (not addressed)
A list passed as a parameter for `T.label` or `T.labels` (e.g.
`property(T.labels, x)` with `x` bound to a list) fails with a
`ClassCastException`. This bug predates this PR and also affects `T.label`, so
it will be tracked separately.
> Add T.labels as an analogue for labels()
> ----------------------------------------
>
> Key: TINKERPOP-3274
> URL: https://issues.apache.org/jira/browse/TINKERPOP-3274
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 4.0.0
> Reporter: Cole Greer
> Priority: Major
>
> Following the introduction of optional multilabel vertices to the TinkerPop
> data model, and the corresponding introduction of a `labels()` step to
> replace the old `label()` step, we should also introduce a new `T.labels`
> token for complete symmetry.
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