Port r152 from branches/5.0: Account for a race condition when dropping the

adaptive hash index for a B-tree page.  (Bug #16582)

btr_search_drop_page_hash_index(): Retry the operation if a hash index
with different parameters was built meanwhile.  Add diagnostics for the
case that hash node pointers to the page remain.  This fix is from Heikki.

btr_search_info_update_hash(), btr_search_info_update_slow():
Document the parameter "info" as in/out.

btr/btr0sea.c

@@ -191,7 +191,7 @@ static
 void
 btr_search_info_update_hash(
 /*========================*/
-	btr_search_t*	info,	/* in: search info */
+	btr_search_t*	info,	/* in/out: search info */
 	btr_cur_t*	cursor)	/* in: cursor which was just positioned */
 {
 	dict_index_t*	index;
@@ -452,7 +452,7 @@ Updates the search info. */
 void
 btr_search_info_update_slow(
 /*========================*/
-	btr_search_t*	info,	/* in: search info */
+	btr_search_t*	info,	/* in/out: search info */
 	btr_cur_t*	cursor)	/* in: cursor which was just positioned */
 {
 	buf_block_t*	block;
@@ -912,12 +912,12 @@ btr_search_drop_page_hash_index(
 	ut_ad(!rw_lock_own(&btr_search_latch, RW_LOCK_SHARED));
 	ut_ad(!rw_lock_own(&btr_search_latch, RW_LOCK_EX));
 #endif /* UNIV_SYNC_DEBUG */
-
+retry:
 	rw_lock_s_lock(&btr_search_latch);
 
 	block = buf_block_align(page);
 
-	if (!block->is_hashed) {
+	if (UNIV_LIKELY(!block->is_hashed)) {
 
 		rw_lock_s_unlock(&btr_search_latch);
 
@@ -958,6 +958,8 @@ btr_search_drop_page_hash_index(
 
 	tree_id = btr_page_get_index_id(page);
 	
+	ut_a(0 == ut_dulint_cmp(tree_id, index->id));
+
 	prev_fold = 0;
 
 	heap = NULL;
@@ -992,6 +994,26 @@ btr_search_drop_page_hash_index(
 
 	rw_lock_x_lock(&btr_search_latch);
 
+	if (UNIV_UNLIKELY(!block->is_hashed)) {
+		/* Someone else has meanwhile dropped the hash index */
+
+		goto cleanup;
+	}
+
+	ut_a(block->index == index);
+
+	if (UNIV_UNLIKELY(block->curr_n_fields != n_fields)
+	    || UNIV_UNLIKELY(block->curr_n_bytes != n_bytes)) {
+
+		/* Someone else has meanwhile built a new hash index on the
+		page, with different parameters */
+
+		rw_lock_x_unlock(&btr_search_latch);
+
+		mem_free(folds);
+		goto retry;
+	}
+
 	for (i = 0; i < n_cached; i++) {
 
 		ha_remove_all_nodes_to_page(table, folds[i], page);
@@ -999,8 +1021,20 @@ btr_search_drop_page_hash_index(
 
 	block->is_hashed = FALSE;
 	block->index = NULL;
+cleanup:
+	if (UNIV_UNLIKELY(block->n_pointers)) {
+		/* Corruption */
+		ut_print_timestamp(stderr);
+		fprintf(stderr,
+"  InnoDB: Corruption of adaptive hash index. After dropping\n"
+"InnoDB: the hash index to a page of %s, still %lu hash nodes remain.\n",
+			index->name, (ulong) block->n_pointers);
+		rw_lock_x_unlock(&btr_search_latch);
 
-	rw_lock_x_unlock(&btr_search_latch);
+		btr_search_validate();
+	} else {
+		rw_lock_x_unlock(&btr_search_latch);
+	}
 
 	mem_free(folds);
 }

include/btr0sea.ic

@@ -16,7 +16,7 @@ Updates the search info. */
 void
 btr_search_info_update_slow(
 /*========================*/
-	btr_search_t*	info,	/* in: search info */
+	btr_search_t*	info,	/* in/out: search info */
 	btr_cur_t*	cursor);/* in: cursor which was just positioned */
 
 /************************************************************************