branches/zip: Add clarifying comments that the clustered index record must

be protected from being deleted while any externally stored columns are
being fetched.

row_ext_create(),
row_upd_index_replace_new_col_vals(),
row_upd_index_replace_new_col_vals_index_pos(),
row_sel_sec_rec_is_for_blob(),
row_sel_sec_rec_is_for_clust_rec(): Note that the clustered
index record must be covered by a lock or a page latch.

row_upd_sec_index_entry(), row_upd_clust_rec_by_insert(),
row_undo_mod_upd_exist_sec(): Note that these functions probably
do not obtain an appropriate lock on the clustered index record
before fetching any externally stored columns.

include/row0ext.h

@@ -27,8 +27,11 @@ row_ext_create(
 				dict_col_get_no(); NOT relative to the records
 				in the clustered index */
 	const dtuple_t*	tuple,	/* in: data tuple containing the field
-				references of the externally stored columns;
-				must be indexed by col_no */
+				references of the externally stored
+				columns; must be indexed by col_no;
+				the clustered index record must be
+				covered by a lock or a page latch
+				to prevent deletion (rollback or purge). */
 	ulint		zip_size,/* compressed page size in bytes, or 0 */
 	mem_heap_t*	heap);	/* in: heap where created */
 

include/row0upd.h

@@ -185,7 +185,10 @@ given. */
 void
 row_upd_index_replace_new_col_vals_index_pos(
 /*=========================================*/
-	dtuple_t*	entry,	/* in/out: index entry where replaced */
+	dtuple_t*	entry,	/* in/out: index entry where replaced;
+				the clustered index record must be
+				covered by a lock or a page latch to
+				prevent deletion (rollback or purge) */
 	dict_index_t*	index,	/* in: index; NOTE that this may also be a
 				non-clustered index */
 	const upd_t*	update,	/* in: an update vector built for the index so
@@ -210,7 +213,10 @@ given. */
 void
 row_upd_index_replace_new_col_vals(
 /*===============================*/
-	dtuple_t*	entry,	/* in/out: index entry where replaced */
+	dtuple_t*	entry,	/* in/out: index entry where replaced;
+				the clustered index record must be
+				covered by a lock or a page latch to
+				prevent deletion (rollback or purge) */
 	dict_index_t*	index,	/* in: index; NOTE that this may also be a
 				non-clustered index */
 	const upd_t*	update,	/* in: an update vector built for the

row/row0ext.c

@@ -60,8 +60,11 @@ row_ext_create(
 				dict_col_get_no(); NOT relative to the records
 				in the clustered index */
 	const dtuple_t*	tuple,	/* in: data tuple containing the field
-				references of the externally stored columns;
-				must be indexed by col_no */
+				references of the externally stored
+				columns; must be indexed by col_no;
+				the clustered index record must be
+				covered by a lock or a page latch
+				to prevent deletion (rollback or purge). */
 	ulint		zip_size,/* compressed page size in bytes, or 0 */
 	mem_heap_t*	heap)	/* in: heap where created */
 {

row/row0sel.c

@@ -67,10 +67,13 @@ row_sel_sec_rec_is_for_blob(
 	ulint		mbminlen,	/* in: minimum length of a
 					multi-byte character */
 	ulint		mbmaxlen,	/* in: maximum length of a
-				multi-byte character */
+					multi-byte character */
 	const byte*	clust_field,	/* in: the locally stored part of
-				the clustered index column, including
-				the BLOB pointer */
+					the clustered index column, including
+					the BLOB pointer; the clustered
+					index record must be covered by
+					a lock or a page latch to protect it
+					against deletion (rollback or purge) */
 	ulint		clust_len,	/* in: length of clust_field */
 	const byte*	sec_field,	/* in: column in secondary index */
 	ulint		sec_len,	/* in: length of sec_field */
@@ -104,7 +107,10 @@ row_sel_sec_rec_is_for_clust_rec(
 					when compared with collation */
 	const rec_t*	sec_rec,	/* in: secondary index record */
 	dict_index_t*	sec_index,	/* in: secondary index */
-	const rec_t*	clust_rec,	/* in: clustered index record */
+	const rec_t*	clust_rec,	/* in: clustered index record;
+					must be protected by a lock or
+					a page latch against deletion
+					in rollback or purge */
 	dict_index_t*	clust_index)	/* in: clustered index */
 {
 	const byte*	sec_field;
@@ -2990,8 +2996,8 @@ row_sel_get_clust_rec_for_mysql(
 		    && !row_sel_sec_rec_is_for_clust_rec(
 			    rec, sec_index, clust_rec, clust_index)) {
 			clust_rec = NULL;
-		} else {
 #ifdef UNIV_SEARCH_DEBUG
+		} else {
 			ut_a(clust_rec == NULL
 			     || row_sel_sec_rec_is_for_clust_rec(
 				     rec, sec_index, clust_rec, clust_index));

row/row0umod.c

@@ -637,6 +637,8 @@ row_undo_mod_upd_exist_sec(
 			but alphabetically they stayed the same, e.g.,
 			'abc' -> 'aBc'. */
 
+			/* TODO: lock the clustered index record
+			before fetching BLOBs */
 			row_upd_index_replace_new_col_vals(entry, index,
 							   node->update,
 							   NULL, heap);

row/row0upd.c

@@ -868,7 +868,10 @@ given. */
 void
 row_upd_index_replace_new_col_vals_index_pos(
 /*=========================================*/
-	dtuple_t*	entry,	/* in/out: index entry where replaced */
+	dtuple_t*	entry,	/* in/out: index entry where replaced;
+				the clustered index record must be
+				covered by a lock or a page latch to
+				prevent deletion (rollback or purge) */
 	dict_index_t*	index,	/* in: index; NOTE that this may also be a
 				non-clustered index */
 	const upd_t*	update,	/* in: an update vector built for the index so
@@ -986,7 +989,10 @@ given. */
 void
 row_upd_index_replace_new_col_vals(
 /*===============================*/
-	dtuple_t*	entry,	/* in/out: index entry where replaced */
+	dtuple_t*	entry,	/* in/out: index entry where replaced;
+				the clustered index record must be
+				covered by a lock or a page latch to
+				prevent deletion (rollback or purge) */
 	dict_index_t*	index,	/* in: index; NOTE that this may also be a
 				non-clustered index */
 	const upd_t*	update,	/* in: an update vector built for the
@@ -1440,6 +1446,7 @@ row_upd_sec_index_entry(
 	}
 
 	/* Build a new index entry */
+	/* TODO: lock the clustered index record before fetching BLOBs */
 	row_upd_index_replace_new_col_vals(entry, index, node->update,
 					   NULL, heap);
 
@@ -1562,6 +1569,7 @@ row_upd_clust_rec_by_insert(
 	entry = row_build_index_entry(node->row, node->ext, index, heap);
 	ut_a(entry);
 
+	/* TODO: lock the clustered index record before fetching BLOBs */
 	row_upd_index_replace_new_col_vals(entry, index, node->update,
 					   NULL, heap);