Re: slow DSS large dataset query, help

This might seem like a rather bizarre idea, but try dropping the indexes so you get a hash join, rather than a nested loop join. You could also probably get a bit of a lift by splitting out the month and year so you don't have to do any computation when reading the table. Have you run UPDATE STATISTICS recently? (Probably best to do this first if you haven't! :-) What are the data types of the joining columns? From: sjsyau@my-deja.com > >Informix 7.3 UC3 on SUN. > >This is a DSS system, mostly for query. > >We have this query runs for 4 hours, looking for >methods to improve performance. > >Please help. > >number 0f rows: >Table_A : 30000000 >Table_B : 2400000 >Table_C : 5000 > >INDEX: >Table_A.c1 >Table_B.c1 >TAble_B.(c2,c3) >Table_C.(c2,c3) > >There is no index on Table_A.create_timestamp >because there are only 6 different values. > > >select A.c1, A.c2, A.c3, C.c1 >from Table_A A, Table_B B, Table_C C >where month(A.create_timestamp) = 11 >and year(A.create_timestamp) = 1995 >and A.c1 = B.c1 >and B.c2 = C.c2 >and B.c3 = C.c3> >The Explain OUT: > > >Estimated Cost: 170427 >Estimated # of Rows Returned: 1457 > >1) c: SEQUENTIAL SCAN > >2) b: INDEX PATH > > (1) Index Keys: c2 c3 > Lower Index Filter: (b.c3 = c.c3 AND > b.c2 = c.c2 ) >NESTED LOOP JOIN > > >3) a: INDEX PATH > > Filters: (MONTH (a.create_timestamp ) = 11 AND >YEAR (a.create_timestamp ) =1995 ) > > (1) Index Keys: c1 > Lower Index Filter: a.c1 = b.c1 >NESTED LOOP JOIN > >Onconfig file: > ># Physical Log Configuration > >PHYSDBS dbs_plog # Location >(dbspace) of physical log >PHYSFILE 100000 # Physical log >file size (Kbytes)> ># Logical Log Configuration > >LOGFILES 20 # Number of>logical log files >LOGSIZE 40000 # Logical log size >(Kbytes) > >TBLSPACE_STATS 1> ># System Configuration > >SERVERNUM 2 # Unique id>corresponding to a Dynamic Server in >stance >DBSERVERNAME prod2 # Name of default>database server >DBSERVERALIASES prodshm # List of>alternate dbservernames >NETTYPE ipcshm,1,20,NET # Configure poll>thread(s) for nettype >NETTYPE tlitcp,1,20,CPU # Configure poll>thread(s) for nettype >DEADLOCK_TIMEOUT 60 # Max time to>wait of lock in distributed env. >RESIDENT 1 # Forced residency >flag (Yes = 1, No = 0) >MULTIPROCESSOR 1 # 0 for>single-processor, 1 for multi-processor >NUMCPUVPS 6 # Number of user >(cpu) vps >SINGLE_CPU_VP 0 # If non-zero,>limit number of cpu vps to one >NOAGE 0 # Process aging >AFF_SPROC 0 # Affinity start>processor >AFF_NPROCS 0 # Affinity number>of processors > ># Shared Memory Parameters > >LOCKS 300000 # Maximum number>of locks >BUFFERS 300000 # Maximum number>of shared buffers >NUMAIOVPS 6 # Number of IO vps >PHYSBUFF 32 # Physical log >buffer size (Kbytes) >LOGBUFF 32 # Logical log >buffer size (Kbytes) >LOGSMAX 30 # Maximum number>of logical log files >CLEANERS 50 # Number of buffer >cleaner processes(ST 9/5/99) >#CLEANERS 10 # Number of>buffer cleaner processes >SHMBASE 0xa000000 # Shared memory>base address > # (Release Notes >recommend "0x0A000000L") >SHMVIRTSIZE 2000000 # initial virtual>shared memory segment size >SHMADD 8192 # Size of new>shared memory segments (Kbytes) >SHMTOTAL 0 # Total shared >memory (Kbytes). 0=>unlimited >CKPTINTVL 300 # Check point >interval (in sec) >LRUS 50 # Number of LRU >queues(ST 9/5/99)>#LRUS 8 # Number of LRU >queues >LRU_MAX_DIRTY 30 # LRU percent>dirty begin cleaning limit >LRU_MIN_DIRTY 20 # LRU percent>dirty end cleaning limit >LTXHWM 40 # Long transaction>high water mark percentage >LTXEHWM 50 # Long transaction>high water mark (exclusive) >TXTIMEOUT 0x12c # Transaction >timeout (in sec) >STACKSIZE 32 # Stack size >(Kbytes)> ># System Page Size ># BUFFSIZE - Dynamic Server no longer supports >this configuration parameter. ># To determine the page size used by >Dynamic Server on your platform ># see the last line of output from the >command, 'onstat -b'. > > > > >OFF_RECVRY_THREADS 10 # Default>number of offline worker threads >ON_RECVRY_THREADS 1 # Default number>of online worker threads ># Data Replication Variables ># DRAUTO: 0 manual, 1 retain type, 2 reverse type >DRAUTO 0 # DR automatic>switchover >DRINTERVAL 30 # DR max time>between DR buffer flushes (in sec) >DRTIMEOUT 30 # DR network >timeout (in sec) >DRLOSTFOUND >/usr/informix/7.30.UC3/etc/dr.lostfound > # DR lost+found>file path > ># CDR Variables >CDR_LOGBUFFERS 2048 # size of log >reading buffer pool (Kbytes) >CDR_EVALTHREADS 1,2 # evaluator >threads (per-cpu-vp,additional) >CDR_DSLOCKWAIT 5 # DS lockwait >timeout (seconds) >CDR_QUEUEMEM 4096 # Maximum amount>of memory for any CDR queue (Kb >ytes) > > ># Read Ahead Variables >RA_PAGES 64 # Number of pages>to attempt to read ahead >RA_THRESHOLD 50 # Number of pages>left before next group > > > >DBSPACETEMP >temp01,temp02,temp03,temp04,temp05,temp06,temp07,t >emp08,temp09,t >emp10,temp11,temp12> > >FILLFACTOR 90 # Fill factor for>building indexes > ># method for Dynamic Server to use when >determining current time >USEOSTIME 0 # 0: use internal >time(fast), 1: get time from O >S(slow)> ># Parallel Database Queries (pdq) >MAX_PDQPRIORITY 85 # Maximum allowed>pdqpriority >DS_MAX_QUERIES 10 # Maximum number>of decision support queries >DS_TOTAL_MEMORY 2000000 # Decision support >memory (Kbytes) >DS_MAX_SCANS 100 # Maximum number>of decision support scans >DATASKIP off # List of dbspaces>to skip > > >OPTCOMPIND 2 # To hint the>optimizer > >ONDBSPACEDOWN 2 # Dbspace down >option: 0 = CONTINUE, 1 = ABORT, >2 = WAIT>LBU_PRESERVE 0 # Preserv