我在Orient-DB中遇到了关系。
我的问题是我不知道如何在orient-DB中创建关系？
我阅读了文档并看到它有命令CREATE LINK。但是当我插入新记录并且不运行命令CREATE LINK时，我不知道它是如何创建链接的。
答案 0 :(得分：0)
CREATE LINK仅在从RDBMS导入时才会将FOREIGN KEYS转换为链接。要创建链接，只需将目标的RID放入源对象即可。您使用的是什么API？
答案 1 :(得分：0)
我有一个简单的示例简单
我有两张桌子。发表评论。TABLE POST：
+----+----------------+
| id | title |
+----+----------------+
| 10 | NoSQL movement |
| 20 | New OrientDB |
+----+----------------+
表评论：
+----+--------+--------------+
| id | postId | text |
+----+--------+--------------+
| 0 | 10 | First |
| 1 | 10 | Second |
| 21 | 10 | Another |
| 41 | 20 | First again |
| 82 | 20 | Second Again |
+----+--------+--------------+
所以现在。我运行命令：
CREATE LINK comments TYPE linkset FROM comment.postId To post.id INVERSE.
在表格中将更改为：
TABLE POST：
+----+----------------++----------------+
| id | title | comments
+----+----------------++----------------+
| 10 | NoSQL movement |[#7:0,#7:1,#7:2]
| 20 | New OrientDB |[#7:3,#7:4]
+----+----------------++----------------+
所以现在。我想在评论表中插入一条记录。
我运行此命令：
INSERT INTO COMMENT (id, postId, text) VALUES( 5, 10, 'Six' );
我的问题是我不知道如何发布表可以更新到：
+----+----------------++----------------+
| id | title | comments
+----+----------------++----------------+
| 10 | NoSQL movement |[#7:0,#7:1,#7:2,#7:5]
| 20 | New OrientDB |[#7:3,#7:4]
+----+----------------++----------------+
谢谢！
答案 2 :(得分：0)
你应该使用这个
begin
let a=INSERT INTO COMMENT (id, postId, text) VALUES( 5, 10, 'Six' );
let b=update post add children=$s where @rid=YOUR_POST_RID/ID
commit
return $b;
/ *****更新＃13：0添加孩子=＃12：1您也可以这样做，其中＃13：0是帖子ID，而＃12：1是评论ID ******* *** /
答案 3 :(得分：0)
我正在使用Java API并且想知道维护文档之间关系的最佳实践是什么。现在我这样做：
protected static ODocument addReference(ODocument d1, ODocument d2) {
Collection<ODocument> ref = d1.field(FIELD_ID, OType.LINKSET);
if(ref == null) {
ref = new HashSet<>();
}
ref = new HashSet<>(ref);
ref.add(d2);
return d1.field(FIELD_ID, ref, OType.LINKSET).save();
}
}
但是我经常遇到NPE或ClassCastExceptions所以我怀疑这是正确的方法。
答案 4 :(得分：0)
现在我正在使用这个目前正在按预期工作的课程。
public class DocumentsReferences {
private final static Logger logger = Logger.getLogger(DocumentsReferences.class);
private static void addToReferenceCollection(ODocument orid, String className, String fieldName, ORID value) {
Collection<ORID> refCollection = new HashSet<>(getReferenceCollection(orid, className, fieldName));
refCollection.add(value);
setReferenceCollection(orid, className, fieldName, refCollection);
}
public static void establishMany2ManyRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, ODocument documentSecond, String classNameSecond, String fieldNameSecond) {
// left side
addToReferenceCollection(documentFirst, classNameFirst, fieldNameFirst, documentSecond.getIdentity());
// right side
addToReferenceCollection(documentSecond, classNameSecond, fieldNameSecond, documentFirst.getIdentity());
}
public static void establishMany2OneRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, ODocument documentSecond, String classNameSecond, String fieldNameSecond) {
// left side
setReference(documentFirst, classNameFirst, fieldNameFirst, documentSecond);
// right side
addToReferenceCollection(documentSecond, classNameSecond, fieldNameSecond, documentFirst.getIdentity());
}
public static void establishOne2ManyRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, ODocument documentSecond, String classNameSecond, String fieldNameSecond) {
// left side
addToReferenceCollection(documentFirst, classNameFirst, fieldNameFirst, documentSecond.getIdentity());
// right side
setReference(documentSecond, classNameSecond, fieldNameSecond, documentFirst);
}
public static void establishOne2OneRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, ODocument documentSecond, String classNameSecond, String fieldNameSecond) {
// left side
setReference(documentFirst, classNameFirst, fieldNameFirst, documentSecond);
// right side
setReference(documentSecond, classNameSecond, fieldNameSecond, documentFirst);
}
public static ORID getReference(ODocument document, String className, String fieldName) {
if (isValid(document, className)) {
OIdentifiable result = document.field(fieldName, OType.LINK);
if (result == null) {
return null;
}
return result.getIdentity();
}
throw new IllegalArgumentException("For " + document);
}
public static Collection<ORID> getReferenceCollection(ODocument document, String className, String fieldName) {
if (isValid(document, className)) {
try {
Collection<OIdentifiable> result = document.field(fieldName, OType.LINKSET);
if (result == null) {
return Collections.emptySet();
}
return result.stream().map(identifiable -> identifiable.getIdentity())
.collect(Collectors.toCollection(ArrayList::new));
} catch (Exception e) {
logger.error(e.getLocalizedMessage(), e);
return Collections.emptySet();
}
}
throw new IllegalArgumentException("For " + document);
}
public static boolean isValid(ODocument document, String className) {
return Documents.isValid(document, className);
}
/**
* @return {@link Collection} of {@link ORID ORIDs} of all documents that
* have been deleted during this operation
*/
public static Collection<ORID> releaseMany2ManyRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, Collection<? extends ODocument> documentsSecond, String classNameSecond,
String fieldNameSecond, boolean autoDeleteEmpty) {
Collection<ORID> result = new ArrayList<>();
for (ODocument documentSecond : documentsSecond) {
// left side
boolean documentFirstIsEmpty = removeFromReferenceCollection(documentFirst, classNameFirst, fieldNameFirst,
documentSecond.getIdentity());
if (documentFirstIsEmpty && autoDeleteEmpty && !result.contains(documentFirst.getIdentity())) {
result.add(documentFirst.delete().save().getIdentity());
}
// right side
boolean documentSecondIsEmpty = removeFromReferenceCollection(documentSecond, classNameSecond,
fieldNameSecond, documentFirst.getIdentity());
if (documentSecondIsEmpty && autoDeleteEmpty && !result.contains(documentSecond.getIdentity())) {
result.add(documentSecond.delete().save().getIdentity());
}
}
if (!result.isEmpty()) {
logger.debug("Auto-deleted empty: " + result);
}
return result;
}
/**
* @return {@link Collection} of {@link ORID ORIDs} of all documents that
* have been deleted during this operation
*/
public static Collection<ORID> releaseMany2ManyRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, ODocument documentSecond, String classNameSecond, String fieldNameSecond,
boolean autoDeleteEmpty) {
return releaseMany2ManyRelationship(documentFirst, classNameFirst, fieldNameFirst,
Arrays.asList(documentSecond), classNameSecond, fieldNameSecond, autoDeleteEmpty);
}
public static void releaseMany2OneRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, ODocument documentSecond, String classNameSecond, String fieldNameSecond) {
// left side
setReference(documentFirst, classNameFirst, fieldNameFirst, null);
// right side
removeFromReferenceCollection(documentSecond, classNameSecond, fieldNameSecond, documentFirst.getIdentity());
}
public static void releaseOne2ManyRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, Collection<? extends ODocument> documentsSecond, String classNameSecond,
String fieldNameSecond) {
for (ODocument documentSecond : documentsSecond) {
// left side
removeFromReferenceCollection(documentFirst, classNameFirst, fieldNameFirst, documentSecond.getIdentity());
// right side
setReference(documentSecond, classNameSecond, fieldNameSecond, null);
}
}
public static void releaseOne2ManyRelationship(ODocument documentFirst, String classNameFirst,
String fieldNameFirst, ODocument documentSecond, String classNameSecond, String fieldNameSecond) {
releaseOne2ManyRelationship(documentFirst, classNameFirst, fieldNameFirst, Arrays.asList(documentSecond),
classNameSecond, fieldNameSecond);
}
public static void releaseOne2OneRelationship(ODocument documentFirst, String classNameFirst, String fieldNameFirst,
Collection<? extends ODocument> documentsSecond, String classNameSecond, String fieldNameSecond) {
// left side
setReference(documentFirst, classNameFirst, fieldNameFirst, null);
// right side
for (ODocument documentSecond : documentsSecond) {
setReference(documentSecond, classNameSecond, fieldNameSecond, null);
}
}
public static void releaseOne2OneRelationship(ODocument documentFirst, String classNameFirst, String fieldNameFirst,
ODocument documentSecond, String classNameSecond, String fieldNameSecond) {
releaseOne2OneRelationship(documentFirst, classNameFirst, fieldNameFirst, Arrays.asList(documentSecond),
classNameSecond, fieldNameSecond);
}
/**
* @return {@code true} if reference collection is now empty; {@code false}
* otherwise
*/
private static boolean removeFromReferenceCollection(ODocument orid, String className, String fieldName,
ORID value) {
Collection<ORID> refCollection = new HashSet<>(getReferenceCollection(orid, className, fieldName));
refCollection.remove(value);
setReferenceCollection(orid, className, fieldName, refCollection);
return refCollection.isEmpty();
}
public static void setReference(ODocument document, String className, String fieldName, OIdentifiable reference) {
if (isValid(document, className)) {
document.field(fieldName, reference, OType.LINK).save();
} else
throw new IllegalArgumentException("For " + document);
}
private static void setReferenceCollection(ODocument document, String className, String fieldName,
Collection<? extends ORID> value) {
if (isValid(document, className)) {
document.field(fieldName, value, OType.LINKSET).save();
} else
throw new IllegalArgumentException("For " + document);
}
}