一段存储过程，请大家帮忙优化解决方法

CREATE PROCEDURE "loan".getpayschedule(dat date)    returning varchar(255);        define returnstr varchar(20);    define v_duebillno varchar(20);--借据号    define v_maxcurrentno INTEGER;--最大期次    define v_duebno varchar(20);    define v_sq INTEGER;    define v_paydate varchar(20);    define v_maturedate varchar(10);    define count1 int;    define v_gitid int;--自动id    define v_currentnosc int;--提前还款上一次期次    define v_gitid1 int;    define sql_err,isam_err int;--异常处理    SET DEBUG FILE TO "gittestcom.txt";    let sql_err = 0;    TRACE ON;    begin        on exception set sql_err             delete from Acc_PayScheduleTmp;            delete from acc_payschedule;            trace "sql_err--->"||sql_err;            return "0";        end exception with resume ;        delete from Acc_PayScheduleTmp;        delete from acc_payschedule;        --从核心中间表导入所需数据岛临时表       -- insert into Acc_PayScheduleTmp select  ap.*,TO_CHAR(today,'%Y%m%d')||seqhkjh.NEXTVAL from Acc_PaySchedule1 ap,loanduebill ld where ap.duebillno=ld.duebillno;        insert into Acc_PayScheduleTmp  select contractno,duebillno,currentno,maturedate,currentsum,currentinterest,currentnormalinterest,currentoverdueinterest,currentoffsheetinterest,payoption,paydate,paysum,payinterest,currency,hexinappid,TO_CHAR(today,'%m%d')||seqhkjh.NEXTVAL from Acc_PaySchedule1 where duebillno in('000001000096011001','000001000167011001');        foreach select duebillno into v_duebillno from Acc_PayScheduleTmp            --开始轮循单条借据           let count1=0;           foreach select duebillno,currentno,paydate,maturedate,gitid into v_duebno,v_sq,v_paydate,v_maturedate,v_gitid from Acc_PayScheduleTmp where duebillno=v_duebillno            if(v_sq==2) then--提前还款从2开始                   let count1=count1+1;                   if(count1==2) then --如果第二次提前还款跟新状态                        select max(currentno) into v_maxcurrentno from Acc_PayScheduleTmp where duebillno=v_duebno and currentno>=2 and gitid<v_gitid;                                                foreach select currentno,gitid into v_currentnosc,v_gitid1 from Acc_PayScheduletmp where duebillno=v_duebno and gitid >v_gitid-1                            update Acc_PayScheduleTmp set currentno=v_maxcurrentno+v_currentnosc-1 where duebillno=v_duebillno and gitid=v_gitid1;                        end foreach                end if            end if            end foreach      end foreach      insert into acc_payschedule select contractno,duebillno,currentno,maturedate,currentsum,currentinterest,currentnormalinterest,currentoverdueinterest,currentoffsheetinterest,payoption,paydate,paysum,payinterest,currency,hexinappid from acc_payscheduleTmp;      let returnstr="1";    end    TRACE OFF;    return returnstr;end procedure;