btr0btr.c:

  Improve space utilization if we have 3 kB - 8 kB rows to insert in the order of the primary key
btr0cur.c:
  Fix bug: The row count and key cardinality estimate was grossly too small if each clustered index page only contained one record


innobase/btr/btr0cur.c:
  Fix bug: The row count and key cardinality estimate was grossly too small if each clustered index page only contained one record
innobase/btr/btr0btr.c:
  Improve space utilization if we have 3 kB - 8 kB rows to insert in the order of the primary key

innobase/btr/btr0btr.c

@@ -76,9 +76,6 @@ make them consecutive on disk if possible. From the other file segment
 we allocate pages for the non-leaf levels of the tree.
 */
 
-/* If this many inserts occur sequentially, it affects page split */
-#define BTR_PAGE_SEQ_INSERT_LIMIT	5
-
 /******************************************************************
 Creates a new index page to the tree (not the root, and also not
 used in page reorganization). */
@@ -1086,18 +1083,18 @@ btr_page_get_split_rec_to_left(
 	page = btr_cur_get_page(cursor);
 	insert_point = btr_cur_get_rec(cursor);
 
-	if ((page_header_get_ptr(page, PAGE_LAST_INSERT)
-	    == page_rec_get_next(insert_point))
-	    && (page_header_get_field(page, PAGE_DIRECTION) == PAGE_LEFT)
-	    && ((page_header_get_field(page, PAGE_N_DIRECTION)
-	     	 			>= BTR_PAGE_SEQ_INSERT_LIMIT)
-	     	|| (page_header_get_field(page, PAGE_N_DIRECTION) + 1
-	     	 			>= page_get_n_recs(page)))) {
+	if (page_header_get_ptr(page, PAGE_LAST_INSERT)
+	    == page_rec_get_next(insert_point)) {
 
 	     	infimum = page_get_infimum_rec(page);
 		
-		if ((infimum != insert_point)
-		    && (page_rec_get_next(infimum) != insert_point)) {
+		/* If the convergence is in the middle of a page, include also
+		the record immediately before the new insert to the upper
+		page. Otherwise, we could repeatedly move from page to page
+		lots of records smaller than the convergence point. */
+
+		if (infimum != insert_point
+		    && page_rec_get_next(infimum) != insert_point) {
 
 			*split_rec = insert_point;
 		} else {
@@ -1131,29 +1128,29 @@ btr_page_get_split_rec_to_right(
 	page = btr_cur_get_page(cursor);
 	insert_point = btr_cur_get_rec(cursor);
 
-	if ((page_header_get_ptr(page, PAGE_LAST_INSERT) == insert_point)
-	    && (page_header_get_field(page, PAGE_DIRECTION) == PAGE_RIGHT)
-	    && ((page_header_get_field(page, PAGE_N_DIRECTION)
-	     	 			>= BTR_PAGE_SEQ_INSERT_LIMIT)
-	     	|| (page_header_get_field(page, PAGE_N_DIRECTION) + 1
-	     	 			>= page_get_n_recs(page)))) {
+	/* We use eager heuristics: if the new insert would be right after
+	the previous insert on the same page, we assume that there is a
+	pattern of sequential inserts here. */
+
+	if (page_header_get_ptr(page, PAGE_LAST_INSERT) == insert_point) {
 
 	     	supremum = page_get_supremum_rec(page);
 	     	 			
-		if ((page_rec_get_next(insert_point) != supremum)
-		    && (page_rec_get_next(page_rec_get_next(insert_point))
-			!= supremum)
-		    && (page_rec_get_next(page_rec_get_next(
-					page_rec_get_next(insert_point)))
-			!= supremum)) {
+		if (page_rec_get_next(insert_point) != supremum
+		    && page_rec_get_next(page_rec_get_next(insert_point))
+			!= supremum) {
 
-			/* If there are >= 3 user records up from the insert
-			point, split all but 2 off */
+			/* If there are >= 2 user records up from the insert
+			point, split all but 1 off. We want to keep one because
+			then sequential inserts can use the adaptive hash
+			index, as they can do the necessary checks of the right
+			search position just by looking at the records on this
+			page. */
 		
-			*split_rec = page_rec_get_next(page_rec_get_next(
-					page_rec_get_next(insert_point)));
+			*split_rec = page_rec_get_next(
+					page_rec_get_next(insert_point));
 		} else {
-			/* Else split at inserted record */
+			/* Else split at the new record to insert */
 	     		*split_rec = NULL;
 	     	}
 

innobase/btr/btr0cur.c

@@ -2671,10 +2671,11 @@ btr_estimate_number_of_different_key_vals(
 
 		btr_cur_open_at_rnd_pos(index, BTR_SEARCH_LEAF, &cursor, &mtr);
 		
-		/* Count the number of different key values minus one
-		for each prefix of the key on this index page: we subtract
-		one because otherwise our algorithm would give a wrong
-		estimate for an index where there is just one key value */
+		/* Count the number of different key values for each prefix of
+		the key on this index page. If the prefix does not determine
+		the index record uniquely in te B-tree, then we subtract one
+		because otherwise our algorithm would give a wrong estimate
+		for an index where there is just one key value. */
 
 		page = btr_cur_get_page(&cursor);
 
@@ -2696,6 +2697,9 @@ btr_estimate_number_of_different_key_vals(
 						&matched_bytes);
 
 			for (j = matched_fields + 1; j <= n_cols; j++) {
+				/* We add one if this index record has
+				a different prefix from the previous */
+
 				n_diff[j]++;
 			}
 
@@ -2705,6 +2709,18 @@ btr_estimate_number_of_different_key_vals(
 			rec = page_rec_get_next(rec);
 		}
 		
+		if (n_cols == dict_index_get_n_unique_in_tree(index)) {
+			/* We add one because we know that the first record
+			on the page certainly had a different prefix than the
+			last record on the previous index page in the
+			alphabetical order. Before this fix, if there was
+			just one big record on each clustered index page, the
+			algorithm grossly underestimated the number of rows
+			in the table. */
+
+			n_diff[n_cols]++;
+		}
+
 		total_external_size +=
 				btr_rec_get_externally_stored_len(rec);
 		mtr_commit(&mtr);