On Wed, Feb 25, 2009 at 4:10 PM, Kevin Grittner <kevin.gritt...@wicourts.gov > wrote:
> >>> Farhan Husain <russ...@gmail.com> wrote: > > The machine postgres is running on has 4 GB of RAM. > > In addition to the other suggestions, you should be sure that > effective_cache_size is set to a reasonable value, which would > probably be somewhere in the neighborhood of '3GB'. This doesn't > affect actual RAM allocation, but gives the optimizer a rough idea how > much data is going to be kept in cache, between both the PostgreSQL > shared_memory setting and the OS cache. It can make better choices > with more accurate information. > > -Kevin > I reran the query with new values of work_mem, effective_cache_size and shared_buffers. There is no change in runtime. Here is the output: ingentadb=# show work_mem; work_mem ---------- 16MB (1 row) ingentadb=# show shared_buffers; shared_buffers ---------------- 64MB (1 row) ingentadb=# show effective_cache_size; effective_cache_size ---------------------- 2GB (1 row) ingentadb=# EXPLAIN ANALYZE 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; QUERY PLAN ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Merge Join (cost=698313.99..711229.09 rows=733195 width=134) (actual time=7659407.195..7659418.630 rows=30 loops=1) Merge Cond: ((a0.subj)::text = (a1.subj)::text) -> Sort (cost=84743.03..84822.90 rows=31949 width=208) (actual time=77.269..77.300 rows=30 loops=1) Sort Key: a0.subj Sort Method: quicksort Memory: 24kB -> Nested Loop (cost=0.00..82352.69 rows=31949 width=208) (actual time=4.821..66.390 rows=30 loops=1) -> Index Scan using jena_g1t1_stmt_ixo on jena_g1t1_stmt a0 (cost=0.00..5428.34 rows=487 width=74) (actual time=2.334..2.675 rows=30 loops=1) Index Cond: ((obj)::text = 'Uv:: http://www.utdallas.edu/~farhan.husain/IngentaConnect/issue1_1'::text) Filter: (((prop)::text = 'Uv:: http://prismstandard.org/namespaces/1.2/basic/isPartOf'::text) AND (graphid = 1)) -> Index Scan using jena_g1t1_stmt_ixsp on jena_g1t1_stmt a2 (cost=0.00..157.32 rows=51 width=134) (actual time=2.114..2.119 rows=1 loops=30) Index Cond: (((a2.subj)::text = (a0.subj)::text) AND ((a2.prop)::text = 'Uv:: http://prismstandard.org/namespaces/1.2/basic/startingPage'::text)) Filter: (a2.graphid = 1) -> Materialize (cost=613570.96..627129.46 rows=1084680 width=74) (actual time=7659329.799..7659334.251 rows=31 loops=1) -> Sort (cost=613570.96..616282.66 rows=1084680 width=74) (actual time=7659329.781..7659334.185 rows=31 loops=1) Sort Key: a1.subj Sort Method: external merge Disk: 282480kB -> Seq Scan on jena_g1t1_stmt a1 (cost=0.00..456639.59 rows=1084680 width=74) (actual time=0.042..46465.020 rows=3192000 loops=1) Filter: ((graphid = 1) AND ((prop)::text = 'Uv:: http://www.w3.org/1999/02/22-rdf-syntax-ns#type'::text) AND ((obj)::text = 'Uv::http://metastore.ingenta.com/ns/structure/Article'::text)) Total runtime: 7659420.128 ms (19 rows) I will try out other suggestions posted yesterday now. Thanks, -- Mohammad Farhan Husain Research Assistant Department of Computer Science Erik Jonsson School of Engineering and Computer Science University of Texas at Dallas
