系统函数解决问题：ORA-01795maximum number of expression in a list is 1000

1 概述

需求：
基于ORACLE 数据库建立查询的时候，会碰到这样的问题：
ORA-01795maximum number of expression in a list is 1000
导致这个问题的原因是因为SQL语句中用到了IN字句，结果IN中的元素个数超过了1000导致了这个错误。
实现方案
开发一个系统函数Process1000LimitOfIn("字段", 树或下拉参数)，让其输出
(字段 in (list1) or 字段 in (list2))
函数有两个参数：
第一个参数：字段名，如果是可视化，直接拖字段，如果是原生sql最好用英文双引号括起来，如"table1.A"
第二个参数：smartbi的多选树或下拉框参数，直接拖参数即可

2 自定义函数

自定义函数的设置方法见wiki示例：
（系统函数——自定义函数）
https://history.wiki.smartbi.com.cn/pages/viewpage.action?pageId=21954994

2.1 编写自定义系统函数类Process1000LimitOfIn

package smartbi.freequery.expression.function;
import smartbi.freequery.metadata.SQLPart;
import smartbi.freequery.util.SQLPartType;
import smartbi.util.StringUtil;
public class Process1000LimitOfIn extends Function {
@Override
public boolean checkParams() {
if (params.length==2)
return true;
else
return false;
}
@Override
public void execute() {
String fieldName = params[0].getSqlStr().trim();
fieldName = trim(fieldName,"\"");
fieldName = trim(fieldName,"'");
String fieldValue = params[1].getSqlStr().trim();
String sep = ",";
String[] fieldValueArray = fieldValue.split(sep);
int size = 1000;
long count = Math.round(Math.ceil(((double)fieldValueArray.length)/size));
if(count ==1){
result.add(new SQLPart(SQLPartType.SQLSTR, fieldName + " in (" + fieldValue +")"));
return;
}
//TODO
StringBuilder sqlSb = new StringBuilder();
sqlSb.append("(");
for(int i =0; i<count; i++){
int jLen = (i+1)*size ;
jLen = (jLen>fieldValueArray.length)?fieldValueArray.length:jLen;
StringBuilder sb = new StringBuilder();
for(int j = i*size; j<jLen; j++){
sb.append(fieldValueArray[j]).append(sep);
}
String sbStr = sb.toString();
if(i>0){
sqlSb.append(" or ");
}
sqlSb.append(fieldName + " in (" + sbStr.substring(0, sbStr.length()-sep.length())+")");
}
sqlSb.append(" ) ");
result.add(new SQLPart(SQLPartType.SQLSTR, sqlSb.toString()));
}
private String trim(String srcStr, String toTrimStr){
if(StringUtil.isNullOrEmpty(srcStr)){
return srcStr;
}
srcStr = srcStr.trim();
while(srcStr.startsWith(toTrimStr)){
srcStr = srcStr.substring(toTrimStr.length());
srcStr = srcStr.trim();
}
while(srcStr.endsWith(toTrimStr)){
srcStr = srcStr.substring(0, srcStr.length()-toTrimStr.length());
srcStr = srcStr.trim();
}
return srcStr;
}
@Override
public String getMDXValue() {
return "";
}
}

2.2 编写升级类

该升级类的操作是向知识库t_restree（资源树）表中插入一条数据，父节点为catalog_string（字符串），资源类型为FUNCTION（函数）
该操作用于后面在资源树中新建同名的自定义函数
package smartbi.ext.function.upgrade;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Timestamp;
import org.apache.log4j.Logger;
import smartbi.repository.UpgradeTask;
import smartbi.util.DBType;
/**

• */
  public class UpgradeTask_New extends UpgradeTask {
  /** */
  private static final Logger LOG = Logger.getLogger(UpgradeTask_New.class);
  @Override
  public boolean doUpgrade(Connection conn, DBType type) {
  PreparedStatement prep = null;
  try {
  Statement sta = conn.createStatement();
  ResultSet rs = sta.executeQuery("select c_resid from t_restree where c_resid = 'func_Process1000LimitOfIn'");
  if(!rs.next()){
  prep = conn.prepareStatement("insert into t_restree(c_resid, c_resname, c_resalias, c_pid, c_restype, c_order, c_perm, c_resdesc, c_created, c_lastmodified) values(?, ?, ?, ?, ?, ?, ?, ?, ?, ?)");
  prep.setString(1, "func_Process1000LimitOfIn");
  prep.setString(2, "Process1000LimitOfIn");
  prep.setString(3, "Process1000LimitOfIn");
  prep.setString(4, "catalog_string");
  prep.setString(5, "FUNCTION");
  prep.setInt(6, 9000);
  prep.setString(7, "<Permissions inherited=\"YES\" role=\"ADMINS\"><Permission perm=\"READ\" descend=\"FOLDER_FILE\"/></Permissions>");
  prep.setString(8, "处理多选树参数或下拉框参数超过1000时报错问题，如Process1000LimitOfIn(\"A\",下拉参数)。<br/> 参数1：要过滤的字段名（如 table1.A），如果是可视化查询直接拖字段，如果是原生sql，字段最好加英文双引号,如\"table1.A\"；参数2：树参数或下拉框参数 <br/>返回值：每超过1000个值生成一个or(如(A in (a,b,c。。。) or A in (d,e,f。。。)) )");
  prep.setTimestamp(9, new Timestamp(new java.util.Date().getTime()));
  prep.setTimestamp(10, new Timestamp(new java.util.Date().getTime()));
  prep.executeUpdate();
  prep.close();
  }
  rs.close();
  sta.close();
  return true;
  } catch (SQLException e) {
  LOG.error("Upgrade UpgradeTask_New '" + this.getClass().getPackage().getName() + "' to " + getNewVersion() + " fail.", e);
  return false;
  }
  }
  @Override
  public String getNewVersion() {
  return "0.0.1";
  }
  }