MDEV-15937 Assertion failure 'key->flags & 1' on ALTER TABLE

While the test case crashes a MariaDB 10.2 debug build only,
let us apply the fix to the earliest applicable MariaDB series (10.0)
to avoid any data corruption on a table-rebuilding ALTER TABLE
using ALGORITHM=INPLACE.

innobase_create_key_defs(): Use altered_table->s->primary_key
when a new primary key is being created.

mysql-test/suite/innodb/r/innodb-alter-nullable.result

@@ -51,3 +51,7 @@ WHERE NAME='test/t';
 TABLE_ID	NAME	FLAG	N_COLS	SPACE	FILE_FORMAT	ROW_FORMAT	ZIP_PAGE_SIZE
 #	test/t	1	6	#	Antelope	Compact	0
 DROP TABLE t;
+CREATE TABLE t1(c1 INT) ENGINE=InnoDB;
+ALTER TABLE t1 ADD CONSTRAINT UNIQUE KEY i1(c1);
+ALTER TABLE t1 CHANGE c1 c1 INT NOT NULL,ADD KEY(c1);
+DROP TABLE t1;

mysql-test/suite/innodb/t/innodb-alter-nullable.test

@@ -71,6 +71,11 @@ WHERE NAME='test/t';
 
 DROP TABLE t;
 
+CREATE TABLE t1(c1 INT) ENGINE=InnoDB;
+ALTER TABLE t1 ADD CONSTRAINT UNIQUE KEY i1(c1);
+ALTER TABLE t1 CHANGE c1 c1 INT NOT NULL,ADD KEY(c1);
+DROP TABLE t1;
+
 # Check that all connections opened by test cases in this file are really
 # gone so execution of other tests won't be affected by their presence.
 --source include/wait_until_count_sessions.inc

storage/innobase/handler/handler0alter.cc

@@ -1594,6 +1594,7 @@ innobase_create_index_def(
 
 	if (key_clustered) {
 		DBUG_ASSERT(!(key->flags & HA_FULLTEXT));
+		DBUG_ASSERT(key->flags & HA_NOSAME);
 		index->ind_type |= DICT_CLUSTERED;
 	} else if (key->flags & HA_FULLTEXT) {
 		DBUG_ASSERT(!(key->flags & HA_KEYFLAG_MASK
@@ -1909,14 +1910,9 @@ innobase_create_key_defs(
 		ulint	primary_key_number;
 
 		if (new_primary) {
-			if (n_add == 0) {
-				DBUG_ASSERT(got_default_clust);
-				DBUG_ASSERT(altered_table->s->primary_key
-					    == 0);
-				primary_key_number = 0;
-			} else {
-				primary_key_number = *add;
-			}
+			DBUG_ASSERT(n_add || got_default_clust);
+			DBUG_ASSERT(n_add || !altered_table->s->primary_key);
+			primary_key_number = altered_table->s->primary_key;
 		} else if (got_default_clust) {
 			/* Create the GEN_CLUST_INDEX */
 			index_def_t*	index = indexdef++;

storage/xtradb/handler/handler0alter.cc

@@ -1595,6 +1595,7 @@ innobase_create_index_def(
 
 	if (key_clustered) {
 		DBUG_ASSERT(!(key->flags & HA_FULLTEXT));
+		DBUG_ASSERT(key->flags & HA_NOSAME);
 		index->ind_type |= DICT_CLUSTERED;
 	} else if (key->flags & HA_FULLTEXT) {
 		DBUG_ASSERT(!(key->flags & HA_KEYFLAG_MASK
@@ -1910,14 +1911,9 @@ innobase_create_key_defs(
 		ulint	primary_key_number;
 
 		if (new_primary) {
-			if (n_add == 0) {
-				DBUG_ASSERT(got_default_clust);
-				DBUG_ASSERT(altered_table->s->primary_key
-					    == 0);
-				primary_key_number = 0;
-			} else {
-				primary_key_number = *add;
-			}
+			DBUG_ASSERT(n_add || got_default_clust);
+			DBUG_ASSERT(n_add || !altered_table->s->primary_key);
+			primary_key_number = altered_table->s->primary_key;
 		} else if (got_default_clust) {
 			/* Create the GEN_CLUST_INDEX */
 			index_def_t*	index = indexdef++;