Port r172 from branches/5.0:

Fix bug #17126, CHECK TABLE blocking other queries, by releasing the
btr_search_latch periodically during the adaptive hash table validation.

btr/btr0sea.c

@@ -1600,14 +1600,29 @@ btr_search_validate(void)
 	ulint		n_page_dumps	= 0;
 	ibool		ok		= TRUE;
 	ulint		i;
+	ulint		cell_count;
 	mem_heap_t*	heap		= NULL;
 	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
 	ulint*		offsets		= offsets_;
 	*offsets_ = (sizeof offsets_) / sizeof *offsets_;
 
+	/* How many cells to check before temporarily releasing
+	btr_search_latch. */
+	ulint		chunk_size = 10000;
+	
+	rw_lock_x_lock(&btr_search_latch);
+
+	cell_count = hash_get_n_cells(btr_search_sys->hash_index);
+	
+	for (i = 0; i < cell_count; i++) {
+		/* We release btr_search_latch every once in a while to
+		give other queries a chance to run. */
+		if ((i != 0) && ((i % chunk_size) == 0)) {
+			rw_lock_x_unlock(&btr_search_latch);
+			os_thread_yield();
 			rw_lock_x_lock(&btr_search_latch);
+		}
 		
-	for (i = 0; i < hash_get_n_cells(btr_search_sys->hash_index); i++) {
 		node = hash_get_nth_cell(btr_search_sys->hash_index, i)->node;
 
 		while (node != NULL) {
@@ -1661,10 +1676,21 @@ btr_search_validate(void)
 		}
 	}
 
-	if (!ha_validate(btr_search_sys->hash_index)) {
+	for (i = 0; i < cell_count; i += chunk_size) {
+		ulint end_index = ut_min(i + chunk_size - 1, cell_count - 1);
 		
+		/* We release btr_search_latch every once in a while to
+		give other queries a chance to run. */
+		if (i != 0) {
+			rw_lock_x_unlock(&btr_search_latch);
+			os_thread_yield();
+			rw_lock_x_lock(&btr_search_latch);
+		}
+
+		if (!ha_validate(btr_search_sys->hash_index, i, end_index)) {
 			ok = FALSE;
 		}
+	}
 
 	rw_lock_x_unlock(&btr_search_latch);
 	if (UNIV_LIKELY_NULL(heap)) {

ha/ha0ha.c

@@ -281,20 +281,26 @@ ha_remove_all_nodes_to_page(
 }
 
 /*****************************************************************
-Validates a hash table. */
+Validates a given range of the cells in hash table. */
 
 ibool
 ha_validate(
 /*========*/
 					/* out: TRUE if ok */
-	hash_table_t*	table)	/* in: hash table */
+	hash_table_t*	table,		/* in: hash table */
+	ulint		start_index,	/* in: start index */
+	ulint		end_index)	/* in: end index */
 {
 	hash_cell_t*	cell;
 	ha_node_t*	node;
 	ibool		ok	= TRUE;
 	ulint		i;
 
-	for (i = 0; i < hash_get_n_cells(table); i++) {
+	ut_a(start_index <= end_index);
+	ut_a(start_index < hash_get_n_cells(table));
+	ut_a(end_index < hash_get_n_cells(table));
+
+	for (i = start_index; i <= end_index; i++) {
 
 		cell = hash_get_nth_cell(table, i);
 

include/ha0ha.h

@@ -99,13 +99,15 @@ ha_remove_all_nodes_to_page(
 	ulint		fold,	/* in: fold value */
 	page_t*		page);	/* in: buffer page */
 /*****************************************************************
-Validates a hash table. */
+Validates a given range of the cells in hash table. */
 
 ibool
 ha_validate(
 /*========*/
 					/* out: TRUE if ok */
-	hash_table_t*	table);	/* in: hash table */
+	hash_table_t*	table,		/* in: hash table */
+	ulint		start_index,	/* in: start index */
+	ulint		end_index);	/* in: end index */
 /*****************************************************************
 Prints info of a hash table. */