Changeset: 194837e195b5 for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=194837e195b5
Modified Files:
MonetDB5/src/optimizer/opt_mergetable.mx
Branch: default
Log Message:
added comment
diffs (23 lines):
diff -r fb0afe4d4423 -r 194837e195b5 MonetDB5/src/optimizer/opt_mergetable.mx
--- a/MonetDB5/src/optimizer/opt_mergetable.mx Mon Aug 30 16:46:25 2010 +0200
+++ b/MonetDB5/src/optimizer/opt_mergetable.mx Wed Sep 01 09:19:49 2010 +0200
@@ -1741,6 +1741,19 @@
actions++;
continue;
}
+ /*
+ topn( project (a,b,c) [ x,y,z ])
+ # phase 1 per part
+ a1 = topn_x(a);
+ b1 = topn_x(b1.semijoin(a1));
+ c1 = topn_x(c1.semijoin(b1));
+ x1 = semijoin(x1,c1);
+ y1 = semijoin(y1,c1);
+ z1 = semijoin(z1,c1);
+ # phase 2 (first pack then execute)
+ a = topn_x(pack (a1,a2,a3,an))
+ # incase of sort we need an merge sort operator
+ */
if (match > 0 && (
getModuleId(p) == groupRef ||
getModuleId(p) == aggrRef ||
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