MDEV-17721 Corrupted data dictionary after instant ADD COLUMN

dict_index_t::reconstruct_fields(): Correctly permute the fields
of the columns. The code was totally wrong in MDEV-15562.
It would only work when columns are added last or dropped,
but not when columns are permuted.

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

@@ -534,6 +534,14 @@ a	c
 3	42
 4	42
 DROP TABLE t1;
+CREATE TABLE t1 (i INT) ENGINE=InnoDB ROW_FORMAT=REDUNDANT;
+INSERT INTO t1 SET i=1;
+ALTER TABLE t1 ADD COLUMN b BIT FIRST;
+ALTER TABLE t1 ADD COLUMN v INT AS (i) VIRTUAL;
+SELECT * FROM t1;
+b	i	v
+NULL	1	1
+DROP TABLE t1;
 CREATE TABLE t1
 (id INT PRIMARY KEY, c2 INT UNIQUE,
 c3 POINT NOT NULL DEFAULT ST_GeomFromText('POINT(3 4)'),
@@ -1014,6 +1022,14 @@ a	c
 3	42
 4	42
 DROP TABLE t1;
+CREATE TABLE t1 (i INT) ENGINE=InnoDB ROW_FORMAT=COMPACT;
+INSERT INTO t1 SET i=1;
+ALTER TABLE t1 ADD COLUMN b BIT FIRST;
+ALTER TABLE t1 ADD COLUMN v INT AS (i) VIRTUAL;
+SELECT * FROM t1;
+b	i	v
+NULL	1	1
+DROP TABLE t1;
 CREATE TABLE t1
 (id INT PRIMARY KEY, c2 INT UNIQUE,
 c3 POINT NOT NULL DEFAULT ST_GeomFromText('POINT(3 4)'),
@@ -1494,10 +1510,18 @@ a	c
 3	42
 4	42
 DROP TABLE t1;
+CREATE TABLE t1 (i INT) ENGINE=InnoDB ROW_FORMAT=DYNAMIC;
+INSERT INTO t1 SET i=1;
+ALTER TABLE t1 ADD COLUMN b BIT FIRST;
+ALTER TABLE t1 ADD COLUMN v INT AS (i) VIRTUAL;
+SELECT * FROM t1;
+b	i	v
+NULL	1	1
+DROP TABLE t1;
 disconnect analyze;
 SELECT variable_value-@old_instant instants
 FROM information_schema.global_status
 WHERE variable_name = 'innodb_instant_alter_column';
 instants
-84
+87
 SET GLOBAL innodb_purge_rseg_truncate_frequency= @saved_frequency;

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

@@ -130,11 +130,12 @@ update t1 set f3 = 19;
 select * from t1;
 f1	f3
 1	19
-alter table t1 drop column f1, add column f5 int default 10, algorithm=instant;
+alter table t1 drop column f1, add column f5 tinyint default 10 first,
+algorithm=instant;
 insert into t1 values(4, 10);
 select * from t1;
-f3	f5
-19	10
+f5	f3
+10	19
 4	10
 create table t2(f1 int, f2 int not null) engine=innodb;
 insert into t2(f1, f2) values(1, 2);
@@ -154,8 +155,8 @@ create table t3(f1 int, f2 int not null)engine=innodb;
 insert into t3 values(1, 2);
 alter table t3 drop column f2, add column f3 int default 1, add column f4 int default 4, algorithm=instant;
 select * from t1;
-f3	f5
-19	10
+f5	f3
+10	19
 4	10
 alter table t1 add column f6 int default 9,drop column f5, algorithm = instant;
 insert into t1 values(4, 9);
@@ -163,7 +164,7 @@ alter table t1 force, algorithm=inplace;
 select * from t1;
 f3	f6
 19	9
-4	9
+10	9
 4	9
 select * from t2;
 f1	f4	f5	f6

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

@@ -410,6 +410,13 @@ UPDATE t1 SET a=a+2;
 SELECT * FROM t1;
 DROP TABLE t1;
 
+eval CREATE TABLE t1 (i INT) $engine;
+INSERT INTO t1 SET i=1;
+ALTER TABLE t1 ADD COLUMN b BIT FIRST;
+ALTER TABLE t1 ADD COLUMN v INT AS (i) VIRTUAL;
+SELECT * FROM t1;
+DROP TABLE t1;
+
 dec $format;
 }
 disconnect analyze;

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

@@ -64,7 +64,8 @@ alter table t1 drop column f2, add column f3 int default 3, algorithm=instant;
 select * from t1;
 update t1 set f3 = 19;
 select * from t1;
-alter table t1 drop column f1, add column f5 int default 10, algorithm=instant;
+alter table t1 drop column f1, add column f5 tinyint default 10 first,
+algorithm=instant;
 insert into t1 values(4, 10);
 select * from t1;
 

storage/innobase/dict/dict0mem.cc

@@ -1217,17 +1217,23 @@ inline void dict_index_t::reconstruct_fields()
 	ulint n_core_null = 0;
 	const bool comp = dict_table_is_comp(table);
 	const auto* non_pk_col_map = table->instant->non_pk_col_map;
-	for (unsigned i = n_first, o = i, j = 0; i < n_fields; ) {
+	for (unsigned i = n_first, j = 0; i < n_fields; ) {
 		dict_field_t& f = tfields[i++];
 		auto c = *non_pk_col_map++;
 		if (c & 1U << 15) {
 			f.col = &table->instant->dropped[j++];
-			ut_ad(f.col->is_dropped());
+			DBUG_ASSERT(f.col->is_dropped());
 			f.fixed_len = dict_col_get_fixed_size(f.col, comp);
 		} else {
-			f = fields[o++];
-			f.col = dict_table_get_nth_col(table, c);
-			f.name = f.col->name(*table);
+			const auto old = std::find_if(
+				fields + n_first, fields + n_fields,
+				[c](const dict_field_t& o)
+				{ return o.col->ind == c; });
+			ut_ad(old >= &fields[n_first]);
+			ut_ad(old < &fields[n_fields]);
+			DBUG_ASSERT(!old->prefix_len);
+			DBUG_ASSERT(old->col == &table->cols[c]);
+			f = *old;
 		}
 
 		f.col->clear_instant();