Changeset: f5629e7c3ee7 for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=f5629e7c3ee7
Modified Files:
gdk/gdk_group.c
Branch: Dec2016
Log Message:
By doing what we say, subgrouping can be a lot faster.
This should fix bug 6317.
diffs (42 lines):
diff --git a/gdk/gdk_group.c b/gdk/gdk_group.c
--- a/gdk/gdk_group.c
+++ b/gdk/gdk_group.c
@@ -838,17 +838,10 @@ BATgroup_internal(BAT **groups, BAT **ex
size_t nmelen;
Heap *hp = NULL;
BUN prb;
- BUN mask = HASHmask(b->batCount) >> 3;
- int bits = 3;
+ BUN mask;
+ int bits;
GDKclrerr(); /* not interested in BAThash errors */
- /* when combining value and group-id hashes,
- * we left-shift one of them by half the hash-mask width
- * to better spread bits and use the entire hash-mask,
- * and thus reduce collisions */
- while (mask >>= 1)
- bits++;
- bits /= 2;
/* not sorted, and no pre-existing hash table: we'll
* build an incomplete hash table on the fly--also see
@@ -873,8 +866,17 @@ BATgroup_internal(BAT **groups, BAT **ex
mask = 1 << 16;
bits = 8;
} else {
+ /* when combining value and group-id hashes,
+ * we left-shift one of them by half the
+ * hash-mask width to better spread bits and
+ * use the entire hash-mask, and thus reduce
+ * collisions */
+ mask = HASHmask(b->batCount) >> 3;
+ bits = 3;
+ while (mask >>= 1)
+ bits++;
+ bits /= 2;
mask = HASHmask(b->batCount);
- bits = 0;
}
if ((hp = GDKzalloc(sizeof(Heap))) == NULL ||
(hp->farmid = BBPselectfarm(TRANSIENT, b->ttype, hashheap))
< 0 ||
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