Help with concurrent insertions.

Hi all,

I am having problems with concurrent transactions. For my application I am running the following commands -
        SELECT pointid,pointtype,pointname,createtime FROM pointtable p ,ebihistory e WHERE p.pointid = e.pointnumber AND e.flag='0'   

        After executing this query, I do an update as follows -
        UPDATE ebihistory SET flag='1' 
But inbetween the SELECT and the UPDATE query, few more tuples are added into ebihistory table with flag='0'. So the UPDATE command updates the flag field of the newly inserted tuples also. As a result I am not able to track the newly inserted tuples.

As a work around I tried to use a function which locks the table to do the above operations, but it doesn't seem to work. There is something wrong with the function that I have written.

create type PointData as(PointId integer,PointType integer,CreateTime bigint);
create or replace function PP_PointBuildInfo() returns setof PointData as '
Declare
rec PointData;
begin
        LOCK TABLE EBIHistory SHARE UPDATE EXCLUSIVE MODE;
        for rec in SELECT pointid,pointtype,pointname,createtime
                FROM pointtable p ,ebihistory e WHERE p.pointid = e.pointnumber AND e.flag=''0'' loop
                return next rec;
        end loop;
        update ebihistory set flag=''1'';
        COMMIT;
end;
' language 'plpgsql';

Could anyone help me out with this.

Regards,
Pradeep