btr0sea.h, btr0sea.c:

Fix a crash in page_dir_find_owner_slot if an adaptive hash index search coincides with purge or an insert


innobase/btr/btr0sea.c:
  Fix a crash in page_dir_find_owner_slot if an adaptive hash index search coincides with purge or an insert
innobase/include/btr0sea.h:
  Fix a crash in page_dir_find_owner_slot if an adaptive hash index search coincides with purge or an insert

innobase/btr/btr0sea.c

@@ -508,6 +508,14 @@ btr_search_check_guess(
 /*===================*/
 				/* out: TRUE if success */
 	btr_cur_t*	cursor,	/* in: guessed cursor position */
+	ibool           can_only_compare_to_cursor_rec,
+	                        /* in: if we do not have a latch on the page
+				of cursor, but only a latch on
+			        btr_search_latch, then ONLY the columns
+				of the record UNDER the cursor are
+				protected, not the next or previous record
+				in the chain: we cannot look at the next or
+				previous record to check our guess! */
 	dtuple_t* 	tuple,	/* in: data tuple */
 	ulint		mode,	/* in: PAGE_CUR_L, PAGE_CUR_LE, PAGE_CUR_G,
 				or PAGE_CUR_GE */
@@ -566,6 +574,13 @@ btr_search_check_guess(
 		}
 	}
 
+	if (can_only_compare_to_cursor_rec) {
+	        /* Since we could not determine if our guess is right just by
+	        looking at the record under the cursor, return FALSE */
+
+	        return(FALSE);
+	}
+
 	match = 0;
 	bytes = 0;
 
@@ -670,6 +685,7 @@ btr_search_guess_on_hash(
 	ulint		fold;
 	ulint		tuple_n_fields;
 	dulint		tree_id;
+	ibool           can_only_compare_to_cursor_rec = TRUE;
 #ifdef notdefined
 	btr_cur_t	cursor2;
 	btr_pcur_t	pcur;
@@ -744,6 +760,8 @@ btr_search_guess_on_hash(
 			goto failure;
 		}
 
+		can_only_compare_to_cursor_rec = FALSE;
+
 		buf_page_dbg_add_level(page, SYNC_TREE_NODE_FROM_HASH);
 	}
 
@@ -775,7 +793,15 @@ btr_search_guess_on_hash(
 				fold);
 */				
 	} else {
-		success = btr_search_check_guess(cursor, tuple, mode, mtr);
+	        /* If we only have the latch on btr_search_latch, not on the
+		page, it only protects the columns of the record the cursor
+		is positioned on. We cannot look at the next of the previous
+		record to determine if our guess for the cursor position is
+		right. */
+
+		success = btr_search_check_guess(cursor,
+				               can_only_compare_to_cursor_rec,
+					       tuple, mode, mtr);
 	}
 	
 	if (!success) {

innobase/include/btr0sea.h

@@ -234,10 +234,16 @@ struct btr_search_sys_struct{
 extern btr_search_sys_t*	btr_search_sys;
 
 /* The latch protecting the adaptive search system: this latch protects the
-(1) positions of records on those pages where a hash index has been built.
-NOTE: It does not protect values of non-ordering fields within a record from
-being updated in-place! We can use fact (1) to perform unique searches to
-indexes. */
+(1) hash index;
+(2) columns of a record to which we have a pointer in the hash index;
+
+but does NOT protect:
+
+(3) next record offset field in a record;
+(4) next or previous records on the same page.
+
+Bear in mind (3) and (4) when using the hash index.
+*/
 
 extern rw_lock_t*	btr_search_latch_temp;