Query Planner (con’t)

Ruiwen Chenhttp://www.site.uottawa.ca/~rchen052/csi3130/

CSI 3130 – 2009 – Lab 7

Installation and InitializationCompile:

cd postgresql-8.4.1./configure --enable-debug --enable-cassert --enable-depend --prefix=/home/rwchen/pginstallmake install

Initialization:cd ../pginstall/bin./initdb –D../data

Start the server:./postgres –D../data –p 5678

Start a client:./psql postgres –p 5678

Start the server with single backend:./postgres --single –D../data postgres(use Ctrl+D to exit)

Change to your own directory (use pwd to get current path)

Change to a random port number to avoid conflicts

Querying Single Relation• Initialize a table

– drop table cust; drop sequence seq_cust;

– create table cust(cid int primary key, name char(40), bno int); – create sequence seq_cust; create index cust_bno on cust(bno);

– insert into cust values(nextval('seq_cust'), 'aaaaaaaaaaaaaaaaaaaaaaa', (random()*50)::int);

– insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; – insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust;

Check stat info• \d cust• select * from pg_stat_user_tables;• analyse verbose cust;• select * from pg_stat_user_tables;• select * from pg_stat_user_indexes;

• insert into cust select nextval('seq_cust'), name, (random()*50)::int from cust; • select * from pg_stat_user_tables;

• update cust set bno = bno+5 where bno>20;• vacuum full analyse cust;• select * from pg_stat_user_tables;

• select * from pg_class where relname='cust';• select relname, relpages, reltuples from pg_class where relname='cust';

Explain Queries• explain select * from cust where cid = 102; • explain select * from cust where cid < 102; • explain select * from cust where cid > 102;

• explain analyse select * from cust where cid = 102; • explain analyse select * from cust where cid < 102; • explain analyse select * from cust where cid > 102;

• \timing • select * from cust where cid = 102; • select * from pg_stat_user_indexes;• select * from cust where cid = 102; • select * from pg_stat_user_indexes;

• explain analyse select * from cust where cid < 102; • select * from pg_stat_user_indexes;

Change planner options• set enable_indexscan=off;• explain analyse select * from cust where cid = 102; • explain analyse select * from cust where cid < 102; • explain analyse select * from cust where cid > 102;

• set enable_bitmapscan=off;• explain analyse select * from cust where cid = 102;

• set enable_indexscan=on;• set enable_seqscan=off;• explain analyse select * from cust where cid = 102; • explain analyse select * from cust where cid < 102; • explain analyse select * from cust where cid > 102;

Enable the Debug Option in Planner

• Shutdown the server• Edit– src/backend/optimizer/plan/planner.c– src/backend/optimizer/path/allpaths.c– Add “#define OPTIMIZER_DEBUG”

• Make install• Restart the server, and try– explain analyse select * from cust where cid = 102;

Join Queries• Add another table

– drop table branch; drop sequence seq_br; – create table branch(bno int primary key, name char(40), region int); – create sequence seq_br; – insert into branch values(nextval('seq_br'),

'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb', (random()*10)::int); – insert into branch select nextval('seq_br'), name, (random()*10)::int from

branch; – insert into branch select nextval('seq_br'), name, (random()*10)::int from

branch; – insert into branch select nextval('seq_br'), name, (random()*10)::int from

branch; – insert into branch select nextval('seq_br'), name, (random()*10)::int from

branch; – insert into branch select nextval('seq_br'), name, (random()*10)::int from

branch;

Join• explain analyse select * from cust, branch where

cust.bno = branch.bno order by branch.region;

• set enable_hashjoin = off; • explain analyse select * from cust, branch where

cust.bno = branch.bno order by branch.region;

• set enable_mergejoin = off; • explain analyse select * from cust, branch where

cust.bno = branch.bno order by branch.region;

Join

• set enable_indexscan = off; • explain analyse select * from cust, branch where

cust.bno = branch.bno order by branch.region;

• set enable_bitmapscan = off; • set enable_mergejoin = on; • explain analyse select * from cust, branch where

cust.bno = branch.bno order by branch.region;

Modify Source Codes

• src/backend/optimizer/plan/planmain.c– Line 85: query_planner()

• Generate a plan

• src/backend/optimizer/plan/allpaths.c– Line 86: make_one_relation()

• Find all paths to generate a result relation– Line 166: set_rel_pathlist()– Line 214: set_plain_rel_pathlist()

• Build paths for a base relation

• /src/backend/optimizer/util/pathnode.c– Line 397: create_seqscan_path()