MDEV-34474 InnoDB: Failing assertion: stat_n_leaf_pages > 0 in ha_innobase::estimate_rows_upper_bound

- Column stat_value and sample_size in mysql.innodb_index_stats
table is declared as BIGINT UNSIGNED without any check constraint.
user manually updates the value of stat_value and sample_size
to zero. InnoDB aborts the server while reading the statistics
information because InnoDB expects at least one leaf
page to exist for the index.

- To fix this issue, InnoDB should interpret the value of
stat_n_leaf_pages, stat_index_size in innodb_index_stats
stat_clustered_index_size, stat_sum_of_other_index_sizes
in innodb_table_stats as valid one even though user
mentioned it as 0.

mysql-test/suite/innodb/r/innodb_stats_fetch.result

@@ -174,3 +174,13 @@ SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_VIRTUAL LIMIT ROWS EXAMINED 5;
 SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN LIMIT ROWS EXAMINED 5;
 SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN_COLS LIMIT ROWS EXAMINED 5;
 DROP TABLE t1;
+#
+#  MDEV-34474 InnoDB: Failing assertion: stat_n_leaf_pages > 0
+#           in ha_innobase::estimate_rows_upper_bound
+#
+CREATE TABLE t (c1 INT,c2 INT,
+INDEX(c1))STATS_PERSISTENT=1 ENGINE=INNODB;
+UPDATE mysql.innodb_index_stats SET stat_value=0 WHERE database_name like "test" and table_name like 't';
+UPDATE mysql.innodb_table_stats SET clustered_index_size= 0, sum_of_other_index_sizes=0 WHERE database_name like "test" and table_name like 't';
+UPDATE t SET c1=+1 ORDER BY c2;
+DROP TABLE t;

mysql-test/suite/innodb/t/innodb_stats_fetch.test

@@ -96,3 +96,15 @@ SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_VIRTUAL LIMIT ROWS EXAMINED 5;
 SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN LIMIT ROWS EXAMINED 5;
 SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN_COLS LIMIT ROWS EXAMINED 5;
 DROP TABLE t1;
+
+--echo #
+--echo #  MDEV-34474 InnoDB: Failing assertion: stat_n_leaf_pages > 0
+--echo #           in ha_innobase::estimate_rows_upper_bound
+--echo #
+
+CREATE TABLE t (c1 INT,c2 INT,
+		INDEX(c1))STATS_PERSISTENT=1 ENGINE=INNODB;
+UPDATE mysql.innodb_index_stats SET stat_value=0 WHERE database_name like "test" and table_name like 't';
+UPDATE mysql.innodb_table_stats SET clustered_index_size= 0, sum_of_other_index_sizes=0 WHERE database_name like "test" and table_name like 't';
+UPDATE t SET c1=+1 ORDER BY c2;
+DROP TABLE t;

storage/innobase/dict/dict0stats.cc

@@ -2665,25 +2665,34 @@ dict_stats_fetch_table_stats_step(
 			break;
 
 		case 1: /* mysql.innodb_table_stats.clustered_index_size */
-
+		{
 			ut_a(dtype_get_mtype(type) == DATA_INT);
 			ut_a(len == 8);
 
 			table->stat_clustered_index_size
-				= (ulint) mach_read_from_8(data);
+				= std::max<ulint>(mach_read_from_8(data), 1);
-
 			break;
+		}
 
 		case 2: /* mysql.innodb_table_stats.sum_of_other_index_sizes */
-
+		{
 			ut_a(dtype_get_mtype(type) == DATA_INT);
 			ut_a(len == 8);
 
-			table->stat_sum_of_other_index_sizes
+			ulint stat_other_idx_size
 				= (ulint) mach_read_from_8(data);
+			if (!stat_other_idx_size
+			    && UT_LIST_GET_LEN(table->indexes) > 1) {
+				stat_other_idx_size
+					= UT_LIST_GET_LEN(table->indexes) - 1;
+			}
+			table->stat_sum_of_other_index_sizes
+				= std::max<ulint>(
+				    mach_read_from_8(data),
+				    UT_LIST_GET_LEN(table->indexes) - 1);
 
 			break;
-
+		}
 		default:
 
 			/* someone changed SELECT
@@ -2866,12 +2875,14 @@ dict_stats_fetch_index_stats_step(
 
 	if (stat_name_len == 4 /* strlen("size") */
 	    && strncasecmp("size", stat_name, stat_name_len) == 0) {
-		index->stat_index_size = (ulint) stat_value;
+		index->stat_index_size
+			= std::max<ulint>(stat_value, 1);
 		arg->stats_were_modified = true;
 	} else if (stat_name_len == 12 /* strlen("n_leaf_pages") */
 		   && strncasecmp("n_leaf_pages", stat_name, stat_name_len)
 		   == 0) {
-		index->stat_n_leaf_pages = (ulint) stat_value;
+		index->stat_n_leaf_pages
+			= std::max<ulint>(stat_value, 1);
 		arg->stats_were_modified = true;
 	} else if (stat_name_len == 12 /* strlen("n_page_split") */
 		   && strncasecmp("n_page_split", stat_name, stat_name_len)
@@ -2951,7 +2962,8 @@ dict_stats_fetch_index_stats_step(
 		index->stat_n_diff_key_vals[n_pfx - 1] = stat_value;
 
 		if (sample_size != UINT64_UNDEFINED) {
-			index->stat_n_sample_sizes[n_pfx - 1] = sample_size;
+			index->stat_n_sample_sizes[n_pfx - 1] =
+				std::max<ib_uint64_t>(sample_size, 1);
 		} else {
 			/* hmm, strange... the user must have UPDATEd the
 			table manually and SET sample_size = NULL */