通过 PostgreSQL 数据库上的简单 java 查询获取 nextval 序列值
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Get nextval sequence value by simple java Query on a PostgreSQL DB
提问by Quentin T.
I'm working on a PostgreSQL Database and I am trying to recover a nextvalsequence by a simple Query by Java, but It's not working :
我正在处理一个 PostgreSQL 数据库，我试图nextval通过一个简单的 Java 查询来恢复一个序列，但它不起作用：
Query q = entityManager.createQuery("SELECT nextval(numcallcartnewcart) as num");
BigDecimal result=(BigDecimal)q.getSingleResult();
return result.longValue();
(Of course it's not the best solution, but I can't do better, because I'm blocked by the Hibernate configuration with the composite-id tag which don't accept a generator sequence like that :
（当然，这不是最好的解决方案，但我不能做得更好，因为我被 Hibernate 配置阻止了，它带有不接受这样的生成器序列的复合 ID 标签：
<column name="num_call" />
<generator class="sequence">
<param name="sequence">numcallcartnewcart</param>
</generator>
into the key-property tag :
进入关键属性标签：
<key-property name="numCall" type="int">
<column name="num_call"/>
</key-property>
) Here is the error of the Query:
) 这是查询的错误：
\-[METHOD_CALL] MethodNode: '('
+-[METHOD_NAME] IdentNode: 'nextval' {originalText=nextval}
\-[EXPR_LIST] SqlNode: 'exprList'
\-[IDENT] IdentNode: 'numcallcartnewcart' {originalText=numcallcartnewcart}
at org.hibernate.hql.ast.tree.SelectClause.initializeExplicitSelectClause(SelectClause.java:154)
at org.hibernate.hql.ast.HqlSqlWalker.useSelectClause(HqlSqlWalker.java:845)
at org.hibernate.hql.ast.HqlSqlWalker.processQuery(HqlSqlWalker.java:633)
It's more or less the same with a createNativeQuery (but not the same error) :
它或多或少与 createNativeQuery 相同（但错误不同）：
Caused by: org.postgresql.util.PSQLException: ERROR: column ? numcallcartnewcart ? does not exist
Position: 16
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2101)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1834)
EDIT : With quote
编辑：带报价
Query q = entityManager.createNativeQuery("SELECT nextval('numcallcartnewcart') as num");
BigDecimal result=(BigDecimal)q.getSingleResult();
return result.longValue();
--
——
Caused by: org.postgresql.util.PSQLException: ERREUR: la relation ? numcallcartnewcart ? n'existe pas
Position: 16
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2101)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1834)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)
EDIT 2 : (The problem was that I don't have the sequence in my database (not in the good one...)
编辑 2 :(问题是我的数据库中没有序列（不是好的......）
And we have to use a BigInteger, not a BigDecimal, and to use quote around sequence name :
我们必须使用 BigInteger，而不是 BigDecimal，并在序列名称周围使用引号：
Query q = entityManager.createNativeQuery("SELECT nextval('numcallcartnewcart') as num");
BigInteger result=(BigInteger)q.getSingleResult();
return result.longValue();
回答by a_horse_with_no_name
The name of the sequence has to be passed as a string literal, not as an identifier:
序列的名称必须作为字符串文字传递，而不是作为标识符：
entityManager.createQuery("SELECT nextval('numcallcartnewcart') as num");
More details in the manual: http://www.postgresql.org/docs/current/static/functions-sequence.html
手册中的更多详细信息：http: //www.postgresql.org/docs/current/static/functions-sequence.html
Edit
编辑
The error
错误
ERREUR: la relation ? numcallcartnewcart ? n'existe pas
错误：关系？numcallcartnewcart ? 不存在的过去
indicates that no sequence with the name numcallcartnewcartexists. You need to create the sequence first.
表示不numcallcartnewcart存在具有该名称的序列。您需要先创建序列。
