Hello,
I am doing a performance comparison between running
Jena with MySQL and Postgres. I used the 8.3-community version of Postgres and MySQL 5.0.67. I have run several queries to both MySQL and Postgres and all of them took similar amount of time to execute except one. For the following query to a table having 10,003,728 rows, MySQL takes 0.11 seconds to return results whereas Postgres takes like 1 hour and 20 minutes!
Query:
select A0.Subj, A2.Obj From jena_g1t1_stmt A0, jena_g1t1_stmt A1, jena_g1t1_stmt A2 Where A0.Prop='Uv::
http://prismstandard.org/namespaces/1.2/basic/isPartOf' AND A0.Obj='Uv::
http://www.utdallas.edu/~farhan.husain/IngentaConnect/issue1_1' AND A0.GraphID=1 AND A0.Subj=A1.Subj AND A1.Prop='Uv::
http://www.w3.org/1999/02/22-rdf-syntax-ns#type' AND A1.Obj='Uv::
http://metastore.ingenta.com/ns/structure/Article' AND A1.GraphID=1 AND A0.Subj=A2.Subj AND A2.Prop='Uv::
http://prismstandard.org/namespaces/1.2/basic/startingPage' AND A2.GraphID=1;
Table:
Table "public.jena_g1t1_stmt"
Column | Type | Modifiers
---------+--------------------
----+-----------
subj | character varying(250) | not null
prop | character varying(250) | not null
obj | character varying(250) | not null
graphid | integer |
Indexes:
"jena_g1t1_stmt_ixo" btree (obj)
"jena_g1t1_stmt_ixsp" btree (subj, prop)
Machine: SunOS 5.10 Generic_127111-11 sun4u sparc SUNW, Sun-Fire-880
Memory: 4 GB
Number of physical processors: 2
I tried to re-arrage the query but each time the amount of time needed is the same. Can anyone help me find the answer to why Postgres is taking so much time?
I can provide any other information needed and also the data if anyone wants.
Thanks and regards,
--
Mohammad Farhan Husain
Research Assistant
Department of Computer Science
Erik Jonsson School of Engineering and Computer Science
University of Texas at Dallas
