branches/zip: Assert that only leaf pages of clustered indexes may contain

externally stored columns.  Make some use of the fact in compression and
decompression.

rec_init_offsets(): Add ut_ad(dict_index_is_clust(index)) before flagging
external columns.

page_zip_get_trailer_len(): Assert ut_ad(!page_zip->n_blobs) unless
dict_index_is_clust(index).

page_zip_get_n_prev_extern(): Add ut_ad(dict_index_is_clust(index)).

page_zip_compress(), page_zip_decompress_low(): Add dict_index_is_clust()
assertions.  Allow completely external storage of columns.  Simplify
the computation of "externs".

page_zip_write_rec(): Store leaf node records of non-clustered indexes
with one memcpy(), avoiding rec_offs_n_extern() and the for loop.

page_zip_write_blob_ptr(): Add ut_ad(dict_index_is_clust(index)).
Simplify the computation of "externs".

page_zip_clear_rec(): Only attempt to zero out BLOB pointers when
the record belongs to a leaf page of a clustered index.

page_zip_dir_delete(): Take a fast path when the record is
not on a leaf page of a clustered index.
Simplify the computation of "externs".

page_zip_copy(): Assert that n_blobs is zero on anything else than
leaf pages of clustered indexes.

include/page0zip.ic

@@ -173,11 +173,13 @@ page_zip_get_trailer_len(
 	if (UNIV_UNLIKELY(!page_is_leaf((page_t*) page_zip->data))) {
 		uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE
 				+ REC_NODE_PTR_SIZE;
+		ut_ad(!page_zip->n_blobs);
 	} else if (dict_index_is_clust(index)) {
 		uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE
 				+ DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
 	} else {
 		uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE;
+		ut_ad(!page_zip->n_blobs);
 	}
 
 	if (entry_size) {

rem/rem0rec.c

@@ -318,6 +318,9 @@ rec_init_offsets(
 						offs += len & 0x3fff;
 						if (UNIV_UNLIKELY(len
 								& 0x4000)) {
+							ut_ad(
+							dict_index_is_clust(
+								index));
 							len = offs
 							| REC_OFFS_EXTERNAL;
 						} else {