jdbcItemReader 支持分區嗎？

Question

使用 https ://github.com/jberet/jberet-support中的 jdbcItemReader 並希望使用分區來加快處理速度。

分區數（此處為 16）對重復寫入的數據有副作用。 每個分區對相同的數據執行相同的工作，而不是將輸入數據集拆分為 n 個不同的分區。

已編輯：下面的代碼顯示了實現它的正確方法。 注意：您的 SQL 查詢需要返回有序數據：N 個分區，這里是 16，表示 16 個讀卡器將運行查詢！

 <reader ref="jdbcItemReader">
                <properties>
                    <property name="beanType" value="java.util.Map"/>
                    <property name="sql" value="select ......"/>
                    <property name="url"
                              value="jdbc:oracle:thin:......"/>
                    <property name="user" value="......."/>
                    <property name="password" value="....."/>
                    <property name="columnMapping" value="xxxx, xxxx"/>
                    <property name="columnTypes" value="String,String"/>
                    <property name="start" value="#{partitionPlan['partition.start']}"/>
                    <property name="end" value="#{partitionPlan['partition.end']}"/>
                    <!--CONCUR_READ_ONLY: If you set this as a value of the concurrency while creating the ResultSet object you cannot update the contents of the ResultSet you can only read/retrieve them.-->
                    <!--CONCUR_UPDATABLE: If you set this as a value of the concurrency while creating the ResultSet object you can update the contents of the ResultSet.-->
                    <!--TYPE_SCROLL_SENSITIVE: ResultSet is sensitive to the changes that are made in the database i.e. the modifications done in the database are reflected in the ResultSet.-->
                    <property name="resultSetProperties"
                              value="fetchSize=5500, resultSetConcurrency=CONCUR_READ_ONLY,
                              fetchDirection=FETCH_REVERSE,
                              resultSetType=TYPE_SCROLL_SENSITIVE,
                              resultSetHoldability=HOLD_CURSORS_OVER_COMMIT"/>
                </properties>
            </reader>
            <processor ref="myProcessort"/>
            <writer ref="myWriter"/>
        </chunk>

<!-- run your sql with a count to define partitions evenly -->
        <partition>
            <plan partitions="16" threads="16">
                <properties partition="0">
                    <property name="partition.start" value="0"/>
                    <property name="partition.end" value="500"/>
                </properties>
                <properties partition="1">
                    <property name="partition.start" value="500"/>
                    <property name="partition.end" value="1000"/>
                </properties>
       <!-- ... -->
                <properties partition="15">
                    <property name="partition.start" value="5000"/>
                    <property name="partition.end" value="5500"/>
                </properties>

Answer 1

您需要像在第二個 XML 代碼段中那樣定義步驟分區。 然后在jdbcItemReader中定義start和end屬性，這兩個屬性分別引用分區屬性partition.start和partition.end 。

這 2 個分區屬性可以命名不同，只要它們在partition和item-reader元素中是一致的。

例如，

<reader ref="jdbcItemReader">
  <properties>
    <property name="start" value="#{partitionPlan['partition.start']}"/>
    <property name="end" value="#{partitionPlan['partition.end']}"/>
</properties>
</reader>