Update of /cvsroot/monetdb/MonetDB5/src/optimizer
In directory sc8-pr-cvs16.sourceforge.net:/tmp/cvs-serv22937
Modified Files:
opt_joinpath.mx
Log Message:
Revert Martin code because it does not work. The code will remain, but commented
for future improvements as Martin suggested...
Index: opt_joinpath.mx
===================================================================
RCS file: /cvsroot/monetdb/MonetDB5/src/optimizer/opt_joinpath.mx,v
retrieving revision 1.21
retrieving revision 1.22
diff -u -d -r1.21 -r1.22
--- opt_joinpath.mx 7 Feb 2008 16:57:18 -0000 1.21
+++ opt_joinpath.mx 7 Feb 2008 17:44:59 -0000 1.22
@@ -231,22 +231,30 @@
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.SAMPLE_THRESHOLD_lOG
+results.
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.
+The model is derived from the select statement. However, we did not succeed.
+The code is now commented for future improvement.
+Final conclusion from this exercise is:
+The difference between the join input size and the join output size is not
+the correct (or unique) metric which should be used to decide which order
+should be used in the joinPath.
+
@c
-#define SAMPLE_THRESHOLD_lOG 17
+/*#define SAMPLE_THRESHOLD_lOG 17*/
size_t
ALGjoinCost(BAT *l, BAT *r)
{
- size_t lc, rc, lsize,rsize;
- BAT *lsample, *rsample, *j;
+ size_t lc, rc;
+/* size_t lsize,rsize;
+ BAT *lsample, *rsample, *j; */
lc = BATcount(l);
rc = BATcount(r);
- if( lc > 100000 || rc > 100000){
+/* if( lc > 100000 || rc > 100000){
lsize= MIN(lc/100, (1<<SAMPLE_THRESHOLD_lOG)/3);
lsample= BATsample(l,lsize);
BBPreclaim(lsample);
@@ -257,7 +265,7 @@
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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