On Tue, Jul 23, 2013 at 12:40 PM, tubadzin <tubad...@o2.pl> wrote: > Hi. > I want add Zigzag Merge join to Index Nested Loops Join alghoritm. > http://www.cs.berkeley.edu/~fox/summaries/database/query_eval_5-8.html > Which files are responsible for Index nested loops join ? (not simple nested > loops join which has double foreach in nodeNestloop.c) nodeIndexscan.c? > nodeIndexonlyscan.c? > Best Regards > Tom
As far as I can tell, a "zigzag merge" is nothing more than a nested loop which uses an index scan on both the inner and outer. It seems a bit strange to me to draw a box around that particular combination and give it a specific name. If that is what it really is, then there is nothing to implement. PostgreSQL already does that when it thinks it is faster than the alternatives. pgbench -i -s10 set enable_seqscan TO off; set enable_mergejoin TO off; set enable_hashjoin TO off; explain select * from pgbench_accounts join pgbench_branches using (bid) where aid between 1 and 5; QUERY PLAN ------------------------------------------------------------------------------------------------------ Nested Loop (cost=0.58..25.21 rows=4 width=457) -> Index Scan using pgbench_accounts_pkey on pgbench_accounts (cost=0.43..8.51 rows=4 width=97) Index Cond: ((aid >= 1) AND (aid <= 5)) -> Index Scan using pgbench_branches_pkey on pgbench_branches (cost=0.14..4.16 rows=1 width=364) Index Cond: (bid = pgbench_accounts.bid) Cheers, Jeff -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers