Apache OFBiz 委托人 API 是否支持按限制或偏移量从数据库中获取记录列表 [英] Does Apache OFBiz delegator API support fetching list of records from database by limit or offset

问题描述

假设我们只需要从表中获取 5 条记录，但我的 where 子句匹配数据库中的 25k 条记录.那么在 ofbiz 框架中有没有办法只选择 5 条记录，而不是从数据库中获取一个列表，然后从列表中只取 5 个?

Let's say we have to fetch only 5 records from a table but my where clause is matching 25k records in the database. So is there a way in ofbiz framework to just select 5 records rather than getting a list from the database and then taking just 5 from the list?

如果限制是不可能的(因为 ofbiz API 与数据库无关)我还有哪些其他选择?

If the limit is not possible (since ofbiz API is database agnostic) what are my other alternatives?

推荐答案

我建议你看看这个 实体引擎手册

基本上是为了从数据库中获取有限的行集，你会这样做:

Essentially for getting limited set of rows from database you would do:

// first get a list iterator
productsELI = delegator.findListIteratorByCondition("Product", 
  new EntityExpr("productId", EntityOperator.NOT_EQUAL, null), 
                  UtilMisc.toList("productId"), null);

// then get a partial list by count TO RETURN first 5 records
productsELI.getPartialList(0, 5);

// and finally just close the iterator
productsELI.close();

此外，如果您希望将直接 SQL 发送到您的数据库，那么就这样做:

Also if you prefer to send direct SQL to your database then just do like this:

// gets the helper (localmysql, localpostgres, etc.) for your entity group org.ofbiz
String helperName = delegator.getGroupHelperName("org.ofbiz");
SQLProcessor sqlproc = new SQLProcessor(helperName);
sqlproc.prepareStatement("SELECT * FROM PARTY LMIT 0, 5");
ResultSet rs1 = sqlproc.executeQuery();

// and then get your data from ResultSet like regular JDBC

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