Update of /cvsroot/monetdb/MonetDB5/src/optimizer
In directory sc8-pr-cvs16.sourceforge.net:/tmp/cvs-serv18894
Modified Files:
opt_joinpath.mx
Log Message:
Experimental sample based join path optimization.
Index: opt_joinpath.mx
===================================================================
RCS file: /cvsroot/monetdb/MonetDB5/src/optimizer/opt_joinpath.mx,v
retrieving revision 1.20
retrieving revision 1.21
diff -u -d -r1.20 -r1.21
--- opt_joinpath.mx 28 Jan 2008 06:14:30 -0000 1.20
+++ opt_joinpath.mx 7 Feb 2008 16:57:18 -0000 1.21
@@ -231,17 +231,33 @@
The join path optimizer takes a join sequence and
attempts to minimize the intermediate result.
The choice depends on a good estimate of intermediate
-results.
+results.SAMPLE_THRESHOLD_lOG
For the time being, we use a simplistic model, based
on the assumption that most joins are foreign key joins anyway.
+We use a sample based approach for sizeable tables.
+The model is derived from the select statement.
@c
+#define SAMPLE_THRESHOLD_lOG 17
size_t
ALGjoinCost(BAT *l, BAT *r)
{
- size_t lc, rc;
+ size_t lc, rc, lsize,rsize;
+ BAT *lsample, *rsample, *j;
lc = BATcount(l);
rc = BATcount(r);
+ if( lc > 100000 || rc > 100000){
+ lsize= MIN(lc/100, (1<<SAMPLE_THRESHOLD_lOG)/3);
+ lsample= BATsample(l,lsize);
+ BBPreclaim(lsample);
+ rsize= MIN(rc/100, (1<<SAMPLE_THRESHOLD_lOG)/3);
+ rsample= BATsample(r,rsize);
+ BBPreclaim(rsample);
+ j= BATjoin(l,r, MAX(lsize,rsize));
+ lsize= BATcount(j);
+ BBPreclaim(j);
+ return lsize;
+ }
if( l->ttype== TYPE_oid || r->htype== TYPE_oid )
return MIN(lc,rc);
return lc * rc;
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