Changeset: 93e4d15fe948 for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=93e4d15fe948
Modified Files:
Branch: default
Log Message:
propagated new comments from Jun2010 branch:
added comments that briefly explain the intentions of
why and how to resort to sort-merge join for large
out of memory joins
diffs (108 lines):
diff -r cfbfaf940bb2 -r 93e4d15fe948 MonetDB/src/gdk/gdk_relop.mx
--- a/MonetDB/src/gdk/gdk_relop.mx Sun May 09 10:48:35 2010 +0200
+++ b/MonetDB/src/gdk/gdk_relop.mx Sun May 09 13:58:39 2010 +0200
@@ -1293,23 +1293,30 @@
required (i.e., re-order allowed) */
BAT *ls, *rs, *j;
+ /* if not yet sorted on tail, sort left input on tail */
ls = BATtordered(l) & 1 ? l :
BATmirror(BATsort(BATmirror(l)));
ERRORcheck(ls == NULL, "BATjoin:
BATmirror(BATsort(BATmirror(l))) failed");
+ /* if not yet sorted on head, sort right input on head
*/
rs = BAThordered(r) & 1 ? r : BATsort(r);
ERRORcheck(rs == NULL, "BATjoin: BATsort(r) failed");
if (swap && rsize > lsize) {
+ /* left-order-preserving not required: user
smaller input as inner (right) */
+ /* (not sure, though, whether this makes a
difference with merge-join ...) */
ALGODEBUG THRprintf(GDKout, "#BATjoin:
BATmirror(BATmergejoin(BATmirror(BATsort(r)), BATsort(BATmirror(l)), " BUNFMT
"));\n", estimate);
j = BATmirror(batmergejoin(BATmirror(rs),
BATmirror(ls), estimate, swap, NULL));
ERRORcheck(j == NULL, "BATjoin:
BATmirror(batmergejoin(BATmirror(rs), BATmirror(ls), estimate, swap, NULL))
failed");
} else {
+ /* left-order-preserving required, or inner
(right) input is smaller one */
ALGODEBUG THRprintf(GDKout, "#BATjoin:
BATmergejoin(BATmirror(BATsort(BATmirror(l))), BATsort(r), " BUNFMT "));\n",
estimate);
j = batmergejoin(ls, rs, estimate, swap, NULL);
ERRORcheck(j == NULL, "BATjoin:
batmergejoin(ls, rs, estimate, swap, NULL) failed");
}
if (ls != l) {
+ /* release temp. tail-ordered copy of left
input */
BBPunfix(ls->batCacheid);
}
if (rs != r) {
+ /* release temp. head-ordered copy of right
input */
BBPunfix(rs->batCacheid);
}
return j;
@@ -1324,20 +1331,28 @@
BAT *ls, *rs, *jj, *j;
ALGODEBUG THRprintf(GDKout, "#BATjoin:
BAT[s]sort(BATmergejoin(BATmirror(BAT[s]sort(BATmirror(l))), BATsort(r), "
BUNFMT "));\n", estimate);
+ /* sort left input on tail, use stable sort to maintain
original order of duplicate head values */
ls = BAThkey(l) ? BATmirror(BATsort(BATmirror(l))) :
BATmirror(BATssort(BATmirror(l)));
ERRORcheck(ls == NULL, "BATjoin:
BATmirror(BAT[s]sort(BATmirror(l))) failed");
+ /* if not yet sorted on head, sort right input on head
*/
rs = BAThordered(r) & 1 ? r : BATsort(r);
ERRORcheck(rs == NULL, "BATjoin: BATsort(r) failed");
+ /* perform merge join */
jj = batmergejoin(ls, rs, estimate, swap, NULL);
ERRORcheck(jj == NULL, "BATjoin: batmergejoin(ls, rs,
estimate, swap, NULL) failed");
+ /* release temp. tail-ordered copy of left input */
BBPunfix(ls->batCacheid);
ls = NULL;
if (rs != r) {
+ /* release temp. head-ordered copy of right
input */
BBPunfix(rs->batCacheid);
rs = NULL;
}
+ /* sort join result on head to restore physical
left-input-order;
+ * use stable sort to maintain original order of
duplicate head values */
j = BAThkey(l) ? BATsort(jj) : BATssort(jj);
ERRORcheck(j == NULL, "BATjoin: BAT[s]sort(jj) failed");
+ /* release temp. unordered join result */
BBPunfix(jj->batCacheid);
jj = NULL;
return j;
@@ -1352,32 +1367,44 @@
BAT *lh, *lt, *ls, *rs, *jj, *js, *j;
ALGODEBUG THRprintf(GDKout, "#BATjoin:
BATmirror(batfetchjoin(BATmirror(BATsort(BATmergejoin(BATmirror(BATsort(BATmark(BATmirror(l),0))),
BATsort(r), " BUNFMT "))), BATmirror(BATmark(l,0))));\n", estimate);
+ /* separate left head & tail using BATmark */
lh = BATmark(l, 0);
ERRORcheck(lh == NULL, "BATjoin: BATmark(l,0) failed");
lt = BATmirror(BATmark(BATmirror(l), 0));
ERRORcheck(lt == NULL, "BATjoin:
BATmirror(BATmark(BATmirror(l),0)) failed");
+ /* sort left tail */
ls = BATmirror(BATsort(BATmirror(lt)));
ERRORcheck(ls == NULL, "BATjoin:
BATmirror(BATsort(BATmirror(lt))) failed");
+ /* release temp. unsorted left tail */
BBPunfix(lt->batCacheid);
lt = NULL;
+ /* if not yet sorted on head, sort right input on head
*/
rs = BAThordered(r) & 1 ? r : BATsort(r);
ERRORcheck(rs == NULL, "BATjoin: BATsort(r) failed");
+ /* perform merge join */
jj = batmergejoin(ls, rs, estimate, swap, NULL);
ERRORcheck(jj == NULL, "BATjoin: batmergejoin(ls, rs,
estimate, swap, NULL) failed");
+ /* release temp. ordered copy of left tail */
BBPunfix(ls->batCacheid);
ls = NULL;
if (rs != r) {
+ /* release temp. head-ordered copy of right
input */
BBPunfix(rs->batCacheid);
rs = NULL;
}
+ /* sort join result on head to restore physical
left-input-order */
js = BATsort(jj);
ERRORcheck(js == NULL, "BATjoin: BATsort(jj) failed");
+ /* release temp. unordered join result */
BBPunfix(jj->batCacheid);
jj = NULL;
+ /* restore original left head values */
j = BATmirror(batfetchjoin(BATmirror(js),
BATmirror(lh), BATcount(js), swap, TRUE));
ERRORcheck(j == NULL, "BATjoin:
BATmirror(batfetchjoin(BATmirror(js), BATmirror(lh), BATcount(js), swap, TRUE))
failed");
+ /* release temp.sorted join result */
BBPunfix(js->batCacheid);
js = NULL;
+ /* release temp. copy of left head */
BBPunfix(lh->batCacheid);
lh = NULL;
return j;
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