oracle里大数据保存至CLOB解决方法

如果数据太大，我们无法对clob变量直接赋值，这时我们可以通过dbms_lob.read、dbms_lob.write方法分阶段的读取和写入clob变量内。但这时我们应该对clob变量建立缓存，如下的第一句。这里给出一个示例程序，可以通过变换dbms_lob.read和dbms_lob.write顺序使程序不仅能写入大数据还能读取大数据。



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dbms_lob.createtemporary(lob_loc => x_clob,
                             cache   => TRUE);
PROCEDURE load_clob(p_clob_in IN CLOB,
                      x_clob    IN OUT NOCOPY CLOB) IS
     
    l_clob_len NUMBER := dbms_lob.getlength(p_clob_in);
    l_data VARCHAR2(32756);
    l_buf_len_std NUMBER := 4000;
    l_buf_len_cur NUMBER;
    l_seg_count   NUMBER;
    l_write_offset NUMBER;
  BEGIN
    IF p_clob_in IS NOT NULL THEN
      l_seg_count := floor(l_clob_len / l_buf_len_std);
      FOR i IN 0 .. l_seg_count
      LOOP
         
        IF i = l_seg_count THEN
          l_buf_len_cur := l_clob_len - i * l_buf_len_std;
        ELSE
          l_buf_len_cur := l_buf_len_std;
        END IF;
         
        IF l_buf_len_cur > 0 THEN
          dbms_lob.read(lob_loc => p_clob_in,
                        amount  => l_buf_len_cur,
                        offset  => i * l_buf_len_std + 1,
                        buffer  => l_data);
          l_write_offset := nvl(dbms_lob.getlength(lob_loc => x_clob),
                                0) + 1;
          dbms_lob.write(lob_loc => x_clob,
                         amount  => l_buf_len_cur,
                         offset  => l_write_offset,
                         buffer  => l_data);
        END IF;
      END LOOP;
    END IF;
  END load_clob;