Re: stracing a connection - Mailing list pgsql-admin

I have  ascheduled pgAgent job which runs monthly executing a stored
procedure which handles some partitoned tables.  Essentially, it
truncated the data in a given partitio and then it changes its rules so
it will be ready to accept the data for its respective next cycle.

The stored procedure follows:



CREATE OR REPLACE FUNCTION fn_cleardata()
  RETURNS void AS
$BODY$
declare
       year            integer;
       month           integer;
       endmonth        integer;
       endyear         integer;
       startoffset     integer;
       endoffset       integer;
       currentdate     date;
       i               integer;
       tablename       varchar;
       startday        integer;
       endday          integer;

begin
     currentdate := CURRENT_DATE;
     month := DATE_PART('month', currentdate)-2;
     year := DATE_PART('year', currentdate);

     if month <=0 then
        month := month+12;
     else
         year := year+1;
     end if;

     startoffset := ((month-1)*4)+1;
     endoffset := startoffset+3;
     startday := 1;
     endday := 9;
     endmonth = month;
     endyear = year;

     for i in startoffset..endoffset loop
         if i < 10 then
            tablename := 'tblksdata' || 0 || i;
         else
            tablename := 'tblksdata' || i;
         end if;
         EXECUTE 'TRUNCATE TABLE '||tablename;
         EXECUTE 'ALTER TABLE '||tablename||' DROP CONSTRAINT
'||tablename||'_datecheck';
         EXECUTE 'ALTER TABLE '||tablename||' ADD CONSTRAINT
'||tablename||'_datecheck
                           CHECK (testtime >=
'''||year||'-'||month||'-'||startday||' 00:00:00''::timestamp without
time zone
                           AND testtime <
'''||endyear||'-'||endmonth||'-'||endday||' 00:00:00''::timestamp
without time zone)';
         EXECUTE 'CREATE OR REPLACE RULE '||tablename||'_rl_insert AS
                           ON INSERT TO tblksdata
                           WHERE new.testtime >=
'''||year||'-'||month||'-'||startday||'''::timestamp without time zone
                           AND new.testtime <
'''||endyear||'-'||endmonth||'-'||endday||'''::timestamp without time
zone
                           DO INSTEAD  INSERT INTO '||tablename||'
(testtime, replyval, statusid, kstestssysid)
                           VALUES (new.testtime, new.replyval,
new.statusid, new.kstestssysid)';

         startday := startday + 8;
         endday := endday + 8;
         if startday = 25 then
            endday = 1;
            endmonth = endmonth + 1;
            if endmonth > 12 then
               endyear := endyear + 1;
               endmonth := endmonth - 12;
            end if;
         end if;
     end loop;
end
$BODY$
  LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION fn_cleardata() OWNER TO postgres;


If I run it manually from pgAdmin during the day it runs fine without
returning an error.  When it runs scheduled, it is returning an error.

At the same time, another function accessing the parent table may be
running, calculating statistical data for the tests.  The partition
which is truncated and whose constraints and rule is being rewritten has
data which is beyond the range of that in the statistical calculation
function, yet I am getting a deadlock.  The error in the pgAgent log
follows:


ERROR: deadlock detected

DETAIL: Process 47642 waits for AccessExclusiveLock on relation 317009
of database 316900; blocked by process 46648.

Process 46648 waits for RowExclusiveLock on relation 317071 of database
316900; blocked by process 47642.

CONTEXT: SQL statement "CREATE OR REPLACE RULE tblksdata21_rl_insert AS

ON INSERT TO tblksdata

WHERE new.testtime >= '2008-6-1'::timestamp without time zone

AND new.testtime < '2008-6-9'::timestamp without time zone

DO INSTEAD INSERT INTO tblksdata21 (testtime, replyval, statusid,
kstestssysid)

VALUES (new.testtime, new.replyval, new.statusid, new.kstestssysid)"

PL/pgSQL function "fn_cleardata" line 43 at execute statement

tblksdata  is the parent table.  The functio running against it is not
updateing any of the data - it is simply calculating aggregates for
specifc rows (max, min, stddev).

Any suggestions would be appreciated.
I am running PostgreSQL 8.1.4 on FreeBSD.