接前文
Session重叠问题学习(二),这是问题和需求的描述,执行时间90秒
http://blog.itpub.net/29254281/viewspace-2150229/
Session重叠问题学习(三)--优化,一次优化后,执行时间25秒
http://blog.itpub.net/29254281/viewspace-2150259/
Session重叠问题学习(四)--再优化,二次优化后,执行时间10秒
http://blog.itpub.net/29254281/viewspace-2150297/
Session重叠问题学习(五)--最优化,三次优化后,执行时间1.6秒
http://blog.itpub.net/29254281/viewspace-2150339/
周五晚上终于把这个算法初步实现了.
连续加班忙碌了一个星期,终于有点曙光了.
从这个问题的缘起,到目前应该已经优化了快100倍了
但是周末的时候,想想还是不对.
小花狸Session合并算法(对,以后这个算法就叫这个名称了)实现的合并速度应该是非常快的.代价仅仅是扫描一遍记录.
这1.6秒到底用在哪里了?
后来经过反复调试.发现还有两块可以优化改进的地方.
改进后的过程如下:
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drop procedure p;
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DELIMITER $$
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CREATE DEFINER=`root`@`localhost` PROCEDURE `p`()
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BEGIN
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declare done int default 0;
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declare v_roomid bigint;
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declare v_time timestamp(6);
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declare v_cur_type smallint;
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declare v_before_roomid bigint default -1;
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declare v_before_type smallint default -1;
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declare v_before_time timestamp(6) ;
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declare v_num bigint default 0;
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declare cur_test CURSOR for select roomid,type,timepoint from tmp_time_point order by roomid,timepoint,type ;
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DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
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drop table if exists t1;
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drop table if exists t2;
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drop table if exists tmp_time_point;
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drop table if exists tmp_result;
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drop table if exists tmp_min_range;
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drop table if exists tmp_s;
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CREATE temporary TABLE `t1` (
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`roomid` int(11) NOT NULL DEFAULT '0',
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`userid` bigint(20) NOT NULL DEFAULT '0',
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`s` timestamp(6),
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`e` timestamp(6),
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primary key(roomid,userid,s,e)
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) ENGINE=memory;
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CREATE temporary TABLE `t2` (
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`roomid` int(11) NOT NULL DEFAULT '0',
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`s` timestamp(6),
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`e` timestamp(6)
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) ENGINE=memory;
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CREATE temporary TABLE `tmp_min_range` (
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`roomid` int(11) NOT NULL DEFAULT '0',
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`s` timestamp(6),
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`e` timestamp(6),
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primary key(roomid,s,e),
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key(roomid,e)
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) ENGINE=memory;
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create temporary table tmp_time_point(
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roomid bigint,
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timepoint timestamp(6),
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type smallint,
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key(roomid,timepoint)
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) engine=memory;
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create temporary table tmp_result(
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roomid bigint,
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timepoint timestamp(6),
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c int
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) engine=memory;
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create temporary table tmp_s(
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roomid bigint,
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userid bigint,
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s timestamp,
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e timestamp,
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i int
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) engine=memory;
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SET @A=0;
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SET @B=0;
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insert into tmp_s
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SELECT x.roomid,x.userid,s,e,datediff(e,s)+1 i
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FROM
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(
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(
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SELECT @B:=@B+1 AS id,roomid,userid,s
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FROM (
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SELECT DISTINCT roomid, userid, roomstart AS s
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FROM u_room_log a
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WHERE NOT EXISTS (SELECT *
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FROM u_room_log b
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WHERE a.roomid = b.roomid
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AND a.userid = b.userid
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AND a.roomstart > b.roomstart
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AND a.roomstart <= b.roomend)
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) AS p
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) AS x,
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(
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SELECT @A:=@A+1 AS id,roomid,userid,e
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FROM
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(
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SELECT DISTINCT roomid, userid, roomend AS e
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FROM u_room_log a
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WHERE NOT EXISTS (SELECT *
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FROM u_room_log b
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WHERE a.roomid = b.roomid
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AND a.userid = b.userid
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AND a.roomend >= b.roomstart
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AND a.roomend < b.roomend)
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) AS o
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) AS y
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)
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WHERE x.id = y.id AND x.roomid = y.roomid AND x.userid = y.userid ;
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select max(i) into @c from tmp_s;
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insert ignore into t1(roomid,userid,s,e)
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select
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roomid, userid,
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if(date(s)!=date(e) and id>1,date(s+interval id-1 date(s+interval id-1 date(e) ,e,date_format(s+interval id-1 '%Y-%m-%d 23:59:59')) e
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from tmp_s t1 STRAIGHT_JOIN
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nums on(nums.id<=t1.i)
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where nums.id<=@c
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;
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insert into t2 (roomid,s,e)
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select roomid,
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s+interval startnum/1000000 second s,
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e-interval endnum/1000000 second e
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from (
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select
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roomid,
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s,e,
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startnum,
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when @eflag=eflag then @rn:=@rn+1 when @eflag:=eflag then @rn else @rn end endnum
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from (
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select * from (
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select when @sflag=sflag then @rn:=@rn+1 when @sflag:=sflag then @rn else @rn end startnum,roomid,s,e,sflag,eflag from
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(
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select * from
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(
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select t1.*,concat('[',roomid,'],',s) sflag,concat('[',roomid,'],',e) eflag from t1 order by roomid ,sflag
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)a,(select @sflag:='',@rn:=0,@eflag:='') vars
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) b
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) bb order by roomid,eflag
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) c
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) d ;
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insert into tmp_time_point(roomid,timepoint,type) select roomid,s,1 from t2;
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insert into tmp_time_point(roomid,timepoint,type) select roomid,e,0 from t2;
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insert ignore into tmp_min_range(roomid,s,e)
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select roomid,starttime starttime, endtime endtime from (
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select
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if(@roomid=roomid,@d,'') as starttime,@d:=str_to_date(timepoint,'%Y-%m-%d %H:%i:%s.%f'),@roomid:=roomid,p.roomid,str_to_date(timepoint,'%Y-%m-%d %H:%i:%s.%f') endtime
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from tmp_time_point p,(select @d:='',@roomid:=-1) vars
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order by roomid,timepoint
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) v4 where starttime!='' and date(starttime)=date(endtime);
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open cur_test;
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repeat
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fetch cur_test into v_roomid,v_cur_type,v_time;
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if done !=1 then
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-- 第一行或者每个房间的第一行
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if v_before_roomid=-1 or v_roomid!=v_before_roomid then
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set v_before_roomid:=v_roomid;
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set v_before_type:=1;
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set v_before_time:='0000-00-00 00:00:00';
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set v_num:=0;
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end if;
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if v_before_type=1 then
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set v_num:=v_num+1;
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insert into tmp_result(roomid,timepoint,c) values(v_roomid,v_time,v_num);
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end if;
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if v_before_type=0 then
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set v_num:=v_num-1;
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insert into tmp_result(roomid,timepoint,c) values(v_roomid,v_time,v_num);
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end if;
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set v_before_roomid:=v_roomid;
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set v_before_type:=v_cur_type;
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set v_before_time:=v_time;
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end if;
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until done end repeat;
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close cur_test;
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select roomid,date(s) dt,round(second,date_format(s,'%Y-%m-%d %H:%i:%s'),date_format(e,'%Y-%m-%d %H:%i:%s')))/60) ts,max(c)-1 c from (
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select a.roomid,a.s,a.e,r.c,r.timepoint from tmp_result r
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inner join
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tmp_min_range a on( r.timepoint=a.e and r.roomid=a.roomid)
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where c>2
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) a group by roomid,date(s);
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END
第一处改进
原来同一房间同一用户重叠时间合并,然后再拆分跨天数据,用的是一条SQL
现在改进如下
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create temporary table tmp_s(
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roomid bigint,
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userid bigint,
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s timestamp,
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e timestamp,
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i int
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) engine=memory;
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SET @A=0;
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SET @B=0;
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insert into tmp_s
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SELECT x.roomid,x.userid,s,e,datediff(e,s)+1 i
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FROM
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(
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(
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SELECT @B:=@B+1 AS id,roomid,userid,s
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FROM (
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SELECT DISTINCT roomid, userid, roomstart AS s
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FROM u_room_log a
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WHERE NOT EXISTS (SELECT *
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FROM u_room_log b
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WHERE a.roomid = b.roomid
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AND a.userid = b.userid
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AND a.roomstart > b.roomstart
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AND a.roomstart <= b.roomend)
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) AS p
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) AS x,
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(
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SELECT @A:=@A+1 AS id,roomid,userid,e
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FROM
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(
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SELECT DISTINCT roomid, userid, roomend AS e
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FROM u_room_log a
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WHERE NOT EXISTS (SELECT *
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FROM u_room_log b
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WHERE a.roomid = b.roomid
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AND a.userid = b.userid
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AND a.roomend >= b.roomstart
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AND a.roomend < b.roomend)
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) AS o
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) AS y
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)
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WHERE x.id = y.id AND x.roomid = y.roomid AND x.userid = y.userid ;
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select max(i) into @c from tmp_s;
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insert ignore into t1(roomid,userid,s,e)
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select
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roomid, userid,
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if(date(s)!=date(e) and id>1,date(s+interval id-1 date(s+interval id-1 date(e) ,e,date_format(s+interval id-1 '%Y-%m-%d 23:59:59')) e
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from tmp_s t1 STRAIGHT_JOIN
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nums on(nums.id<=t1.i)
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where nums.id<=@c
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;
先把同一房间同一用户的重叠部分合并,然后暂存临时表
记录最大的间隔时间,然后再拆分数据
拆分数据的时候 使用STRAIGHT_JOIN 强制连接顺序.
这样避免因为数字辅助表过大,而导致性能陡然变差.
第二处改进
原来使用distinct的查询, 都改为在临时表上增加主键.
然后使用insert ignore into 代替 insert into
这样大概优化了300毫秒
经过反复优化之后,执行时间大致稳定在1250毫秒 至 1300 毫秒
各个部分耗时分析如下
填充tmp_s,合并同一房间同一用户的重叠部分,耗时655毫秒
填充t1,拆分跨天的用户数据,耗时62毫秒
填充t2,用户时间段首尾相交或者首尾全部重合的数据拆分,耗时140毫秒
填充tmp_min_range,计算最小间隔范围,耗时156毫秒
小花狸Session合并算法,耗时219毫秒结果统计展示,耗时47毫秒
网站题目:Session重叠问题学习(六)--极致优化
转载源于:
http://cdkjz.cn/article/jcsggi.html