經過
janusgraph沒有表的概念,但有類似表的schema的定義,稱爲label
。如:我們可以通過graph.openManagement().makeVertexLabel().make()
方法來創建頂點label。那麼存在了類似表的label
,是否就有類似表字段類似的定義,答案是肯定的。janusgraph中用propertykey的定義來替代常用表的屬性作爲解決方案。
但是和關係型數據庫不一樣的是,janusgraph的字段是統一維護在一個池
中。可以簡單地把這個池
理解爲一個集合,而這個集合,維護了該圖的所有label的字段屬性。
我們可以通過執行如下代碼,打印這個圖的池
維護的所有字段。
StandardJanusGraph graph = GraphUtil.getStandardGraphFactory();
JanusGraphManagement mgt = graph.openManagement();
String s4 = mgt.printPropertyKeys();
System.out.println(s4);
打印信息如下:
然後我們可以通過執行如下語句,給該 label進行屬性添加。
@Test
public void testInsertDateData() {
StandardJanusGraph standardGraphFactory = GraphUtil.getStandardGraphFactory();
JanusGraphManagement mgmt = standardGraphFactory.openManagement();
VertexLabel person = mgmt.makeVertexLabel("person").make();
PropertyKey name = mgmt.makePropertyKey("name4").dataType(String.class).cardinality(Cardinality.SET).make();
PropertyKey birthDate = mgmt.makePropertyKey("birthDate").dataType(Date.class).cardinality(Cardinality.SINGLE).make();
mgmt.addProperties(person, name, birthDate);
mgmt.commit();
}
不過在執行的時候,報異常了。
異常信息
org.janusgraph.core.SchemaViolationException: Adding this property for key [~T$SchemaName] and value [rtname4] violates a uniqueness constraint [SystemIndex#~T$SchemaName]
at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.addProperty(StandardJanusGraphTx.java:817)
at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.addProperty(StandardJanusGraphTx.java:745)
at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.makeSchemaVertex(StandardJanusGraphTx.java:873)
at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.makePropertyKey(StandardJanusGraphTx.java:893)
at org.janusgraph.graphdb.types.StandardPropertyKeyMaker.make(StandardPropertyKeyMaker.java:98)
at cn.haizhi.bigdata.graph.client.DataInsertTest.testInsertDateData(DataInsertTest.java:48)
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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
問題排查
如上,我們已經知道,在janusgraph的該圖中的池
中,已經有name4
這個字段了,所以會報異常。
結論
- 同一個字段,只能被建立一次,即使是不同的
label
下創建。 - janusgraph中,圖一個圖下(在存儲上表現爲hbase的表,不同的圖用的是不同的hbase表),只維護一份propertyKey的列表。