batch.po

hibernate-distribution-3.3.1.GA-dist.zip源码

msgid ""
msgstr ""
"Project-Id-Version: PACKAGE VERSION\n"
"Report-Msgid-Bugs-To: http://bugs.kde.org\n"
"POT-Creation-Date: 2008-08-14 15:28+0000\n"
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
"Language-Team: LANGUAGE <[e-mail]>\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"

#. Tag: title
#: batch.xml:29
#, no-c-format
msgid "Batch processing"
msgstr "批量处理（Batch processing）"

#. Tag: para
#: batch.xml:31
#, no-c-format
msgid ""
"A naive approach to inserting 100 000 rows in the database using Hibernate "
"might look like this:"
msgstr ""
"使用Hibernate将 100 000 条记录插入到数据库的一个很自然的做法可能是这样的"

#. Tag: programlisting
#: batch.xml:36
#, no-c-format
msgid ""
"<![CDATA[Session session = sessionFactory.openSession();\n"
"Transaction tx = session.beginTransaction();\n"
"for ( int i=0; i<100000; i++ ) {\n"
"    Customer customer = new Customer(.....);\n"
"    session.save(customer);\n"
"}\n"
"tx.commit();\n"
"session.close();]]>"
msgstr ""

#. Tag: para
#: batch.xml:38
#, no-c-format
msgid ""
"This would fall over with an <literal>OutOfMemoryException</literal> "
"somewhere around the 50 000th row. That's because Hibernate caches all the "
"newly inserted <literal>Customer</literal> instances in the session-level "
"cache."
msgstr ""
"这段程序大概运行到 50 000 条记录左右会失败并抛出 <literal>内存溢出异常"
"（OutOfMemoryException）</literal> 。 这是因为 Hibernate 把所有新插入的 "
"<literal>客户（Customer）</literal>实例在 session级别的缓存区进行了缓存的缘"
"故。"

#. Tag: para
#: batch.xml:44
#, no-c-format
msgid ""
"In this chapter we'll show you how to avoid this problem. First, however, if "
"you are doing batch processing, it is absolutely critical that you enable "
"the use of JDBC batching, if you intend to achieve reasonable performance. "
"Set the JDBC batch size to a reasonable number (say, 10-50):"
msgstr ""
"我们会在本章告诉你如何避免此类问题。首先，如果你要执行批量处理并且想要达到一"
"个理想的性能， 那么使用JDBC的批量（batching）功能是至关重要。将JDBC的批量抓取"
"数量（batch size）参数设置到一个合适值 （比如，10-50之间）："

#. Tag: programlisting
#: batch.xml:51
#, no-c-format
msgid "<![CDATA[hibernate.jdbc.batch_size 20]]>"
msgstr ""

#. Tag: para
#: batch.xml:53
#, no-c-format
msgid ""
"Note that Hibernate disables insert batching at the JDBC level transparently "
"if you use an <literal>identiy</literal> identifier generator."
msgstr ""
"注意,假若你使用了<literal>identiy</literal>标识符生成器,Hibernate在JDBC级别透"
"明的关闭插入语句的批量执行。"

#. Tag: para
#: batch.xml:58
#, no-c-format
msgid ""
"You also might like to do this kind of work in a process where interaction "
"with the second-level cache is completely disabled:"
msgstr "你也可能想在执行批量处理时关闭二级缓存："

#. Tag: programlisting
#: batch.xml:63
#, no-c-format
msgid "<![CDATA[hibernate.cache.use_second_level_cache false]]>"
msgstr ""

#. Tag: para
#: batch.xml:65
#, no-c-format
msgid ""
"However, this is not absolutely necessary, since we can explicitly set the "
"<literal>CacheMode</literal> to disable interaction with the second-level "
"cache."
msgstr ""
"但是，这不是绝对必须的，因为我们可以显式设置<literal>CacheMode</literal>来关"
"闭与二级缓存的交互。"

#. Tag: title
#: batch.xml:71
#, no-c-format
msgid "Batch inserts"
msgstr "批量插入（Batch inserts）"

#. Tag: para
#: batch.xml:73
#, no-c-format
msgid ""
"When making new objects persistent, you must <literal>flush()</literal> and "
"then <literal>clear()</literal> the session regularly, to control the size "
"of the first-level cache."
msgstr ""
"如果要将很多对象持久化，你必须通过经常的调用 <literal>flush()</literal> 以及"
"稍后调用 <literal>clear()</literal> 来控制第一级缓存的大小。"

#. Tag: programlisting
#: batch.xml:79
#, no-c-format
msgid ""
"<![CDATA[Session session = sessionFactory.openSession();\n"
"Transaction tx = session.beginTransaction();\n"
"   \n"
"for ( int i=0; i<100000; i++ ) {\n"
"    Customer customer = new Customer(.....);\n"
"    session.save(customer);\n"
"    if ( i % 20 == 0 ) { //20, same as the JDBC batch size\n"
"        //flush a batch of inserts and release memory:\n"
"        session.flush();\n"
"        session.clear();\n"
"    }\n"
"}\n"
"   \n"
"tx.commit();\n"
"session.close();]]>"
msgstr ""

#. Tag: title
#: batch.xml:84
#, no-c-format
msgid "Batch updates"
msgstr "批量更新（Batch updates）"

#. Tag: para
#: batch.xml:86
#, no-c-format
msgid ""
"For retrieving and updating data the same ideas apply. In addition, you need "
"to use <literal>scroll()</literal> to take advantage of server-side cursors "
"for queries that return many rows of data."
msgstr ""
"此方法同样适用于检索和更新数据。此外，在进行会返回很多行数据的查询时， 你需要"
"使用 <literal>scroll()</literal> 方法以便充分利用服务器端游标所带来的好处。"

#. Tag: programlisting
#: batch.xml:92
#, no-c-format
msgid ""
"<![CDATA[Session session = sessionFactory.openSession();\n"
"Transaction tx = session.beginTransaction();\n"
"   \n"
"ScrollableResults customers = session.getNamedQuery(\"GetCustomers\")\n"
"    .setCacheMode(CacheMode.IGNORE)\n"
"    .scroll(ScrollMode.FORWARD_ONLY);\n"
"int count=0;\n"
"while ( customers.next() ) {\n"
"    Customer customer = (Customer) customers.get(0);\n"
"    customer.updateStuff(...);\n"
"    if ( ++count % 20 == 0 ) {\n"
"        //flush a batch of updates and release memory:\n"
"        session.flush();\n"
"        session.clear();\n"
"    }\n"
"}\n"
"   \n"
"tx.commit();\n"
"session.close();]]>"
msgstr ""

#. Tag: title
#: batch.xml:97
#, no-c-format
msgid "The StatelessSession interface"
msgstr "StatelessSession (无状态session)接口"

#. Tag: para
#: batch.xml:98
#, no-c-format
msgid ""
"Alternatively, Hibernate provides a command-oriented API that may be used "
"for streaming data to and from the database in the form of detached objects. "
"A <literal>StatelessSession</literal> has no persistence context associated "
"with it and does not provide many of the higher-level life cycle semantics. "
"In particular, a stateless session does not implement a first-level cache "
"nor interact with any second-level or query cache. It does not implement "
"transactional write-behind or automatic dirty checking. Operations performed "
"using a stateless session do not ever cascade to associated instances. "
"Collections are ignored by a stateless session. Operations performed via a "
"stateless session bypass Hibernate's event model and interceptors. Stateless "
"sessions are vulnerable to data aliasing effects, due to the lack of a first-"
"level cache. A stateless session is a lower-level abstraction, much closer "
"to the underlying JDBC."
msgstr ""
"作为选择，Hibernate提供了基于命令的API，可以用detached object的形式把数据以流"
"的方法加入到数据库，或从数据库输出。<literal>StatelessSession</literal>没有持"
"久化上下文，也不提供多少高层的生命周期语义。特别是，无状态session不实现第一级"
"cache,也不和第二级缓存，或者查询缓存交互。它不实现事务化写，也不实现脏数据检"
"查。用stateless session进行的操作甚至不级联到关联实例。stateless session忽略"
"集合类(Collections)。通过stateless session进行的操作不触发Hibernate的事件模型"
"和拦截器。无状态session对数据的混淆现象免疫，因为它没有第一级缓存。无状态"
"session是低层的抽象，和低层JDBC相当接近。"

#. Tag: programlisting
#: batch.xml:113
#, no-c-format
msgid ""
"<![CDATA[StatelessSession session = sessionFactory.openStatelessSession();\n"
"Transaction tx = session.beginTransaction();\n"
"   \n"
"ScrollableResults customers = session.getNamedQuery(\"GetCustomers\")\n"
"    .scroll(ScrollMode.FORWARD_ONLY);\n"
"while ( customers.next() ) {\n"
"    Customer customer = (Customer) customers.get(0);\n"
"    customer.updateStuff(...);\n"
"    session.update(customer);\n"
"}\n"
"   \n"
"tx.commit();\n"
"session.close();]]>"
msgstr ""

#. Tag: para
#: batch.xml:115
#, no-c-format
msgid ""
"Note that in this code example, the <literal>Customer</literal> instances "
"returned by the query are immediately detached. They are never associated "
"with any persistence context."
msgstr ""
"注意在上面的例子中，查询返回的<literal>Customer</literal>实例立即被脱管"
"(detach)。它们与任何持久化上下文都没有关系。"

#. Tag: para
#: batch.xml:121
#, no-c-format
msgid ""
"The <literal>insert(), update()</literal> and <literal>delete()</literal> "
"operations defined by the <literal>StatelessSession</literal> interface are "
"considered to be direct database row-level operations, which result in "
"immediate execution of a SQL <literal>INSERT, UPDATE</literal> or "
"<literal>DELETE</literal> respectively. Thus, they have very different "
"semantics to the <literal>save(), saveOrUpdate()</literal> and "
"<literal>delete()</literal> operations defined by the <literal>Session</"
"literal> interface."
msgstr ""
"<literal>StatelessSession</literal> 接口定义的<literal>insert(), update()</"
"literal> 和 <literal>delete()</literal>操作是直接的数据库行级别操作，其结果是"
"立刻执行一条<literal>INSERT, UPDATE</literal> 或 <literal>DELETE</literal> 语"
"句。因此，它们的语义和<literal>Session</literal> 接口定义的<literal>save(), "
"saveOrUpdate()</literal> 和<literal>delete()</literal> 操作有很大的不同。"

#. Tag: title
#: batch.xml:134
#, no-c-format
msgid "DML-style operations"
msgstr "DML(数据操作语言)风格的操作(DML-style operations)"

#. Tag: para
#: batch.xml:136
#, fuzzy, no-c-format
msgid ""
"As already discussed, automatic and transparent object/relational mapping is "
"concerned with the management of object state. This implies that the object "
"state is available in memory, hence manipulating (using the SQL "
"<literal>Data Manipulation Language</literal> (DML) statements: "
"<literal>INSERT</literal>, <literal>UPDATE</literal>, <literal>DELETE</"
"literal>) data directly in the database will not affect in-memory state. "
"However, Hibernate provides methods for bulk SQL-style DML statement "
"execution which are performed through the Hibernate Query Language (<link "
"linkend=\"queryhql\">HQL</link>)."
msgstr ""
"hence manipulating (using the SQL <literal>Data Manipulation Language</"
"literal> (DML) statements: <literal>INSERT</literal>, <literal>UPDATE</"
"literal>, <literal>DELETE</literal>) data directly in the database will not "
"affect in-memory state. However, Hibernate provides methods for bulk SQL-"
"style DML statement execution which are performed through the Hibernate "
"Query Language (<xref linkend=\"queryhql\">HQL</xref>). 就像已经讨论的那样，"
"自动和透明的 对象/关系 映射（object/relational mapping）关注于管理对象的状"
"态。 这就意味着对象的状态存在于内存，因此直接操作 (使用 SQL <literal>Data "
"Manipulation Language</literal>(DML,数据操作语言）语句 ：<literal>INSERT</"
"literal> ,<literal>UPDATE</literal> 和 <literal>DELETE</literal>) 数据库中的"
"数据将不会影响内存中的对象状态和对象数据。 不过，Hibernate提供通过Hibernate查"
"询语言（<xref linkend=\"queryhql\">HQL</xref>）来执行大批 量SQL风格的DML语句"
"的方法。"