branches/innodb+: ibuf0ibuf.c: Revert the patches to Issue #82

(r2962, r2865, r2864) and do not refuse to buffer deletes.  The
problem with refusing to buffer deletes was that no deletes were
buffered.

Instead, when merging delete requests, disregard a delete request
if it would make the page empty.  InnoDB tolerates redundant secondary
index records, but not empty pages.

ibuf_delete(): When merging a delete request, print and ignore the record
if the page would become empty.

ibuf/ibuf0ibuf.c

@@ -2526,114 +2526,6 @@ ibuf_contract_after_insert(
 	}
 }
 
-/*************************************************************************
-Determine if an insert buffer record has been encountered already. */
-static
-ibool
-ibuf_get_volume_buffered_hash(
-/*==========================*/
-				/* out: TRUE if a new record,
-				FALSE if possible duplicate */
-	const rec_t*	rec,	/* in: ibuf record in post-4.1 format */
-	byte*		hash,	/* in/out: hash array */
-	ulint		size)	/* in: size of hash array, in bytes */
-{
-	ulint		len;
-	ulint		fold;
-	const byte*	types;
-	ulint		types_len;
-	ulint		bitmask;
-
-	types = rec_get_nth_field_old(rec, 3, &types_len);
-	len = ibuf_rec_get_size(rec, types, rec_get_n_fields_old(rec) - 4,
-				FALSE);
-	fold = ut_fold_binary(types + types_len, len);
-
-	hash += (fold / 8) % size;
-	bitmask = 1 << (fold % 8);
-
-	if (*hash & bitmask) {
-
-		return(FALSE);
-	}
-
-	/* We have not seen this record yet.  Insert it. */
-	*hash |= bitmask;
-
-	return(TRUE);
-}
-
-/*************************************************************************
-Update the estimate of the number of records on a page. */
-static
-void
-ibuf_get_volume_buffered_count(
-/*===========================*/
-	const rec_t*	rec,	/* in: insert buffer record */
-	byte*		hash,	/* in/out: hash array */
-	ulint		size,	/* in: size of hash array, in bytes */
-	ulint*		n_recs)	/* in/out: estimated number of records
-				on the page that rec points to */
-{
-	ulint		len;
-	const byte*	field;
-	ibuf_op_t	ibuf_op;
-
-	ut_ad(ibuf_inside());
-	ut_ad(rec_get_n_fields_old(rec) > 2);
-
-	field = rec_get_nth_field_old(rec, 1, &len);
-
-	if (UNIV_UNLIKELY(len > 1)) {
-		/* This is a < 4.1.x format record.  Ignore it in the
-		count, because deletes cannot be buffered if there are
-		old-style records for the page. */
-
-		return;
-	}
-
-	field = rec_get_nth_field_old(rec, 3, &len);
-
-	switch (UNIV_EXPECT(len % DATA_NEW_ORDER_NULL_TYPE_BUF_SIZE,
-			    IBUF_REC_INFO_SIZE)) {
-	default:
-		ut_error;
-	case 0:
-	case 1:
-		/* This record does not include an operation counter.
-		Ignore it in the count, because deletes cannot be
-		buffered if there are old-style records for the page. */
-		return;
-
-	case IBUF_REC_INFO_SIZE:
-		ibuf_op = (ibuf_op_t) field[IBUF_REC_OFFSET_TYPE];
-		break;
-	}
-
-	switch (ibuf_op) {
-	case IBUF_OP_INSERT:
-		/* Inserts can be done by
-		btr_cur_set_deleted_flag_for_ibuf().  Because
-		delete-mark and insert operations can be pointing to
-		the same records, we must not count duplicates. */
-	case IBUF_OP_DELETE_MARK:
-		/* There must be a record to delete-mark.
-		See if this record has been already buffered. */
-		if (ibuf_get_volume_buffered_hash(rec, hash, size)) {
-			(*n_recs)++;
-		}
-		break;
-	case IBUF_OP_DELETE:
-		/* A record will be removed from the page. */
-		if (*n_recs > 0) {
-			(*n_recs)--;
-		}
-		break;
-	default:
-		ut_error;
-	}
-}
-
 /*************************************************************************
 Gets an upper limit for the combined size of entries buffered in the insert
 buffer for a given page. */
@@ -2653,8 +2545,6 @@ ibuf_get_volume_buffered(
 				or BTR_MODIFY_TREE */
 	ulint		space,	/* in: space id */
 	ulint		page_no,/* in: page number of an index page */
-	ulint*		n_recs,	/* out: minimum number of records on the page
-				after the buffered changes have been applied */
 	mtr_t*		mtr)	/* in: mtr */
 {
 	ulint	volume;
@@ -2664,7 +2554,6 @@ ibuf_get_volume_buffered(
 	page_t*	prev_page;
 	ulint	next_page_no;
 	page_t*	next_page;
-	byte	hash_bitmap[128]; /* bitmap of buffered records */
 
 	ut_a(trx_sys_multiple_tablespace_format);
 
@@ -2675,7 +2564,6 @@ ibuf_get_volume_buffered(
 	pcur */
 
 	volume = 0;
-	*n_recs = 0;
 
 	rec = btr_pcur_get_rec(pcur);
 	page = page_align(rec);
@@ -2752,8 +2640,6 @@ ibuf_get_volume_buffered(
 	}
 
 count_later:
-	memset(hash_bitmap, 0, sizeof hash_bitmap);
-
 	rec = btr_pcur_get_rec(pcur);
 
 	if (!page_rec_is_supremum(rec)) {
@@ -2774,9 +2660,6 @@ ibuf_get_volume_buffered(
 
 		volume += ibuf_rec_get_volume(rec);
 
-		ibuf_get_volume_buffered_count(
-			rec, hash_bitmap, sizeof hash_bitmap, n_recs);
-
 		rec = page_rec_get_next(rec);
 	}
 
@@ -2824,9 +2707,6 @@ ibuf_get_volume_buffered(
 
 		volume += ibuf_rec_get_volume(rec);
 
-		ibuf_get_volume_buffered_count(
-			rec, hash_bitmap, sizeof hash_bitmap, n_recs);
-
 		rec = page_rec_get_next(rec);
 	}
 }
@@ -3109,7 +2989,6 @@ ibuf_insert_low(
 	dtuple_t*	ibuf_entry;
 	mem_heap_t*	heap;
 	ulint		buffered;
-	ulint		min_n_recs;
 	rec_t*		ins_rec;
 	ibool		old_bit_value;
 	page_t*		bitmap_page;
@@ -3215,16 +3094,7 @@ ibuf_insert_low(
 
 	/* Find out the volume of already buffered inserts for the same index
 	page */
-	buffered = ibuf_get_volume_buffered(&pcur, space, page_no,
-					    &min_n_recs, &mtr);
-
-	if (op == IBUF_OP_DELETE && min_n_recs == 0) {
-		/* The page could become empty after the record is
-		deleted.  Refuse to buffer the operation. */
-		err = DB_STRONG_FAIL;
-
-		goto function_exit;
-	}
+	buffered = ibuf_get_volume_buffered(&pcur, space, page_no, &mtr);
 
 #ifdef UNIV_IBUF_COUNT_DEBUG
 	ut_a((buffered == 0) || ibuf_count_get(space, page_no));
@@ -3642,6 +3512,15 @@ ibuf_delete(
 		offsets = rec_get_offsets(
 			rec, index, offsets, ULINT_UNDEFINED, &heap);
 
+		if (UNIV_UNLIKELY(page_get_n_recs(page) == 1)) {
+			/* Refuse to delete the last record. */
+			ut_print_timestamp(stderr);
+			fputs("  InnoDB: refusing to merge a buffered delete"
+			      " that would make a page empty\n", stderr);
+			rec_print_new(stderr, rec, offsets);
+			goto func_exit;
+		}
+
 		lock_update_delete(block, rec);
 
 		if (!page_zip) {
@@ -3663,6 +3542,7 @@ ibuf_delete(
 			ibuf_update_free_bits_low(block, max_ins_size, mtr);
 		}
 
+func_exit:
 		if (UNIV_LIKELY_NULL(heap)) {
 			mem_heap_free(heap);
 		}