branches/zip: Minor cleanup after r690. One test case still fails.

page_zip_compress_write_log(): Do not invoke page_zip_validate(), since
this is a static function and the callers already invoke page_zip_validate().

page_zip_decompress_low(): Clear the page #ifdef UNIV_ZIP_DEBUG.
Optimizations: Remove local variable "last".  Do not clear the BLOB
pointer until the modification log has been applied.  (Since r690,
it will be cleared after applying the modification log.)
Avoid calling rec_get_offsets() a second time if there are no
uncompressed columns to be restored.

page/page0zip.c

@@ -195,10 +195,6 @@ page_zip_compress_write_log(
 	byte*	log_ptr;
 	ulint	trailer_size;
 
-#ifdef UNIV_ZIP_DEBUG
-	ut_a(page_zip_validate(page_zip, page));
-#endif /* UNIV_ZIP_DEBUG */
-
 	log_ptr = mlog_open(mtr, 11 + 2 + 2);
 
 	if (!log_ptr) {
@@ -1550,6 +1546,10 @@ page_zip_decompress_low(
 	heap = mem_heap_create(n_dense * (3 * sizeof *recs));
 	recs = mem_heap_alloc(heap, n_dense * (2 * sizeof *recs));
 
+#ifdef UNIV_ZIP_DEBUG
+	/* Clear the page. */
+	memset(page, 0x55, UNIV_PAGE_SIZE);
+#endif /* UNIV_ZIP_DEBUG */
 	/* Copy the page header. */
 	memcpy(page, page_zip->data, PAGE_DATA);
 
@@ -1653,20 +1653,17 @@ page_zip_decompress_low(
 
 	/* Decompress the records in heap_no order. */
 	for (slot = 0; slot < n_dense; slot++) {
-		byte* const	last	= d_stream.next_out;
 		rec_t*		rec	= recs[slot];
 
-		d_stream.avail_out = rec - REC_N_NEW_EXTRA_BYTES - last;
+		d_stream.avail_out = rec - REC_N_NEW_EXTRA_BYTES
+				- d_stream.next_out;
 
 		ut_ad(d_stream.avail_out < UNIV_PAGE_SIZE
 			      - PAGE_ZIP_START - PAGE_DIR);
 		switch (inflate(&d_stream, Z_SYNC_FLUSH)) {
 		case Z_STREAM_END:
 			/* Apparently, n_dense has grown
-			since the time the page was last compressed.
-			(d_stream.next_out == last) will not hold,
-			in case the last record was allocated from
-			an originally longer space on the free list. */
+			since the time the page was last compressed. */
 			goto zlib_done;
 		case Z_OK:
 		case Z_BUF_ERROR:
@@ -1765,13 +1762,12 @@ page_zip_decompress_low(
 						goto zlib_error;
 					}
 
-					/* Clear the BLOB pointer in case
+					/* Skip the BLOB pointer in case
 					the record was deleted.  The BLOB
-					pointers of existing records will
-					be copied later from "externs" in
-					this function. */
-					memset(d_stream.next_out, 0,
-						BTR_EXTERN_FIELD_REF_SIZE);
+					pointers will be initialized
+					(copied from "externs" or cleared)
+					only after the page modification log
+					has been applied. */
 					d_stream.next_out
 						+= BTR_EXTERN_FIELD_REF_SIZE;
 				}
@@ -1909,10 +1905,10 @@ page_zip_decompress_low(
 			ibool	exists	= !page_zip_dir_find_free(
 						page_zip, ut_align_offset(
 						rec, UNIV_PAGE_SIZE));
-			offsets = rec_get_offsets(rec, index, offsets,
-					ULINT_UNDEFINED, &heap);
-
 			if (UNIV_UNLIKELY(trx_id_col != ULINT_UNDEFINED)) {
+				offsets = rec_get_offsets(rec, index, offsets,
+						ULINT_UNDEFINED, &heap);
+
 				dst = rec_get_nth_field(rec, offsets,
 						trx_id_col, &len);
 				ut_ad(len >= DATA_TRX_ID_LEN
@@ -1920,6 +1916,15 @@ page_zip_decompress_low(
 				storage -= DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
 				memcpy(dst, storage,
 					DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN);
+
+				if (UNIV_UNLIKELY(!exists)) {
+					continue;
+				}
+			} else if (UNIV_LIKELY(exists)) {
+				offsets = rec_get_offsets(rec, index, offsets,
+						ULINT_UNDEFINED, &heap);
+			} else {
+				continue;
 			}
 
 			/* Check if there are any externally stored