branches/zip: page_cur_insert_rec_zip(): When allocating insert_buf

from the free list, zero out the DB_TRX_ID and DB_ROLL_PTR of the
deleted record if the new record would not overwrite these
fields. This fixes a harmless content mismatch reported by
page_zip_validate() that was reported as Issue #111.
rb://55 approved by Sunny Bains.

page/page0cur.c

@@ -907,7 +907,7 @@ page_cur_insert_rec_low(
 	ulint*		offsets,/* in/out: rec_get_offsets(rec, index) */
 	mtr_t*		mtr)	/* in: mini-transaction handle, or NULL */
 {
-	byte*		insert_buf	= NULL;
+	byte*		insert_buf;
 	ulint		rec_size;
 	page_t*		page;		/* the relevant page */
 	rec_t*		last_insert;	/* cursor position at previous
@@ -1172,7 +1172,7 @@ page_cur_insert_rec_zip(
 	ulint*		offsets,/* in/out: rec_get_offsets(rec, index) */
 	mtr_t*		mtr)	/* in: mini-transaction handle, or NULL */
 {
-	byte*		insert_buf	= NULL;
+	byte*		insert_buf;
 	ulint		rec_size;
 	page_t*		page;		/* the relevant page */
 	rec_t*		last_insert;	/* cursor position at previous
@@ -1285,6 +1285,41 @@ page_cur_insert_rec_zip(
 				    rec_get_next_ptr(free_rec, TRUE),
 				    rec_size);
 
+		if (page_is_leaf(page) && dict_index_is_clust(index)) {
+			/* Zero out the DB_TRX_ID and DB_ROLL_PTR
+			columns of free_rec, in case it will not be
+			overwritten by insert_rec. */
+
+			ulint	trx_id_col;
+			ulint	trx_id_offs;
+			ulint	len;
+
+			trx_id_col = dict_index_get_sys_col_pos(index,
+								DATA_TRX_ID);
+			ut_ad(trx_id_col > 0);
+			ut_ad(trx_id_col != ULINT_UNDEFINED);
+
+			trx_id_offs = rec_get_nth_field_offs(foffsets,
+							     trx_id_col, &len);
+			ut_ad(len == DATA_TRX_ID_LEN);
+
+			if (DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN + trx_id_offs
+			    + rec_offs_extra_size(foffsets) > rec_size) {
+				/* We will have to zero out the
+				DB_TRX_ID and DB_ROLL_PTR, because
+				they will not be fully overwritten by
+				insert_rec. */
+
+				memset(free_rec + trx_id_offs, 0,
+				       DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+			}
+
+			ut_ad(free_rec + trx_id_offs + DATA_TRX_ID_LEN
+			      == rec_get_nth_field(free_rec, foffsets,
+						   trx_id_col + 1, &len));
+			ut_ad(len == DATA_ROLL_PTR_LEN);
+		}
+
 		if (UNIV_LIKELY_NULL(heap)) {
 			mem_heap_free(heap);
 		}