Use cursors for seeking records in SYS_FOREIGN and SYS_INDEXES from

DROP_TABLE_PROC().

With this change I observe a speedup from 6.2s to 0.1s when executing
DROP_TABLE_PROC() during DROP TABLE with 512 foreign keys, like what
is being done in innodb_bug56143.test

This fixes "Bug#11765460 DROP TABLE USES INEFFICIENT METHODS TO REMOVE
FKS/INDEXES FROM INNODB SYS TABLES"

Reviewed by:	Marko

storage/innodb_plugin/row/row0mysql.c

@@ -3221,6 +3221,19 @@ row_drop_table_for_mysql(
 			   "index_id CHAR;\n"
 			   "foreign_id CHAR;\n"
 			   "found INT;\n"
+
+			   "DECLARE CURSOR cur_fk IS\n"
+			   "SELECT ID FROM SYS_FOREIGN\n"
+			   "WHERE FOR_NAME = :table_name\n"
+			   "AND TO_BINARY(FOR_NAME)\n"
+			   "  = TO_BINARY(:table_name)\n"
+			   "LOCK IN SHARE MODE;\n"
+
+			   "DECLARE CURSOR cur_idx IS\n"
+			   "SELECT ID FROM SYS_INDEXES\n"
+			   "WHERE TABLE_ID = table_id\n"
+			   "LOCK IN SHARE MODE;\n"
+
 			   "BEGIN\n"
 			   "SELECT ID INTO table_id\n"
 			   "FROM SYS_TABLES\n"
@@ -3243,13 +3256,9 @@ row_drop_table_for_mysql(
 			   "IF (:table_name = 'SYS_FOREIGN_COLS') THEN\n"
 			   "       found := 0;\n"
 			   "END IF;\n"
+			   "OPEN cur_fk;\n"
 			   "WHILE found = 1 LOOP\n"
-			   "       SELECT ID INTO foreign_id\n"
-			   "       FROM SYS_FOREIGN\n"
-			   "       WHERE FOR_NAME = :table_name\n"
-			   "               AND TO_BINARY(FOR_NAME)\n"
-			   "                 = TO_BINARY(:table_name)\n"
-			   "               LOCK IN SHARE MODE;\n"
+			   "       FETCH cur_fk INTO foreign_id;\n"
 			   "       IF (SQL % NOTFOUND) THEN\n"
 			   "               found := 0;\n"
 			   "       ELSE\n"
@@ -3259,12 +3268,11 @@ row_drop_table_for_mysql(
 			   "               WHERE ID = foreign_id;\n"
 			   "       END IF;\n"
 			   "END LOOP;\n"
+			   "CLOSE cur_fk;\n"
 			   "found := 1;\n"
+			   "OPEN cur_idx;\n"
 			   "WHILE found = 1 LOOP\n"
-			   "       SELECT ID INTO index_id\n"
-			   "       FROM SYS_INDEXES\n"
-			   "       WHERE TABLE_ID = table_id\n"
-			   "       LOCK IN SHARE MODE;\n"
+			   "       FETCH cur_idx INTO index_id;\n"
 			   "       IF (SQL % NOTFOUND) THEN\n"
 			   "               found := 0;\n"
 			   "       ELSE\n"
@@ -3275,6 +3283,7 @@ row_drop_table_for_mysql(
 			   "               AND TABLE_ID = table_id;\n"
 			   "       END IF;\n"
 			   "END LOOP;\n"
+			   "CLOSE cur_idx;\n"
 			   "DELETE FROM SYS_COLUMNS\n"
 			   "WHERE TABLE_ID = table_id;\n"
 			   "DELETE FROM SYS_TABLES\n"