尽管尚未提供属性值，但尝试添加具有属性的顶点会违反唯一性约束

Question

我有一个图表，其顶点带有一个名为fbid的属性，我为其创建了一个具有唯一性约束的索引。使用我添加到Titan库的Java代码并在gremlin shell中手动触发，初始化图形（安装模式并添加一些初始顶点和边缘）发生了：

gremlin> :> com.my.example.TestGraphFactory.loadScheme(graph)
gremlin> :> com.my.example.TestGraphFactory.loadGraph(graph)

现在，我正在尝试这样做：

gremlin> :> g.V().has('fbid', 'fbid_42')
gremlin> :> g.V().addV(label, 'user').property('fbid', 'fbid_42')
Adding this property for key [fbid] and value [fbid_42] violates a uniqueness constraint [fbid]
Display stack trace? [yN] y
org.apache.tinkerpop.gremlin.groovy.plugin.RemoteException: Adding this property for key [fbid] and value [fbid_42] violates a uniqueness constraint [fbid]
at org.apache.tinkerpop.gremlin.console.groovy.plugin.DriverRemoteAcceptor.submit(DriverRemoteAcceptor.java:116)
at org.apache.tinkerpop.gremlin.console.commands.SubmitCommand.execute(SubmitCommand.groovy:41)
at org.codehaus.groovy.tools.shell.Shell.execute(Shell.groovy:101)
at org.codehaus.groovy.tools.shell.Groovysh.super$2$execute(Groovysh.groovy)
at sun.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1207)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:130)
at org.codehaus.groovy.tools.shell.Groovysh.executeCommand(Groovysh.groovy:254)
at org.codehaus.groovy.tools.shell.Groovysh.execute(Groovysh.groovy:153)
at org.codehaus.groovy.tools.shell.Shell.leftShift(Shell.groovy:119)
at org.codehaus.groovy.tools.shell.ShellRunner.work(ShellRunner.groovy:94)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.super$2$work(InteractiveShellRunner.groovy)
at sun.reflect.GeneratedMethodAccessor31.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1207)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:130)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuper0(ScriptBytecodeAdapter.java:150)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.work(InteractiveShellRunner.groovy:123)
at org.codehaus.groovy.tools.shell.ShellRunner.run(ShellRunner.groovy:58)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.super$2$run(InteractiveShellRunner.groovy)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1207)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:130)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuper0(ScriptBytecodeAdapter.java:150)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.run(InteractiveShellRunner.groovy:82)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:215)
at org.apache.tinkerpop.gremlin.console.Console.<init>(Console.groovy:144)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:215)
at org.apache.tinkerpop.gremlin.console.Console.main(Console.groovy:303)

我没有看到原因，因为这实际上是我在建立方案并使用一些第一个顶点和边缘（没有一个具有此特定属性值）初始化图形后所采取的第一个操作。

我应该在哪里看？

Answer 1

原因在于：

gremlin> :> g.V().addV(label, 'user').property('fbid', 'fbid_42')

我太盲目了，在尝试添加新顶点之前，我没有看到我要求获取所有顶点。因此，正确的请求将是

gremlin> :> g.addV(label, 'user').property('fbid', 'fbid_42')