MDEV-16065 Assertion failed in btr_pcur_restore_position_func on UPDATE

btr_pcur_store_position(): Assert that the 'default row' record never
is the only record in a page. (If that would happen, an empty
root page would be re-created in the non-instant format, not containing
the special record.) When the cursor is positioned on the page infimum,
never use the 'default row' as the BTR_PCUR_BEFORE reference.
(This is additional cleanup, not fixing the bug.)

rec_copy_prefix_to_buf(): When converting a record prefix to
the non-instant-add format, copy the original number of null flags.
Rename the variable instant_len to instant_omit, and introduce a
few more variables to make the code easiser to read.

Note: In purge, rec_copy_prefix_to_buf() is also used for storing the
persistent cursor position on a 'default row' record. The stored record
reference will be garbage, but row_search_on_row_ref() will do special
handling to reposition the cursor on the 'default row', based on
ref->info_bits.

innodb.dml_purge: Also cover the 'default row'.

3 files changed, 32 insertions, 8 deletions

diff --git a/mysql-test/suite/innodb/r/dml_purge.result b/mysql-test/suite/innodb/r/dml_purge.result
index eb542484724..95330b80d33 100644
--- a/mysql-test/suite/innodb/r/dml_purge.result
+++ b/mysql-test/suite/innodb/r/dml_purge.result
@@ -11,6 +11,7 @@ connect  prevent_purge,localhost,root;
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
 connection default;
 INSERT INTO t1 VALUES(1,2),(3,4);
+ALTER TABLE t1 ADD COLUMN c INT;
 UPDATE t1 SET b=-3 WHERE a=3;
 connect  con1,localhost,root;
 BEGIN;
@@ -21,8 +22,13 @@ InnoDB		0 transactions not purged
 disconnect con1;
 FLUSH TABLE t1 FOR EXPORT;
 Clustered index root page contents:
-N_RECS=2; LEVEL=0
-header=0x010000030087 (a=0x696e66696d756d00)
+N_RECS=3; LEVEL=0
+header=0x0100000300c6 (a=0x696e66696d756d00)
+header=0x1000200b0087 (a=0x80000000,
+ DB_TRX_ID=0x000000000000,
+ DB_ROLL_PTR=0x80000000000000,
+ b=0x80000000,
+ c=NULL(4 bytes))
 header=0x0000100900a6 (a=0x80000001,
  DB_TRX_ID=0x000000000000,
  DB_ROLL_PTR=0x80000000000000,
@@ -31,11 +37,11 @@ header=0x000018090074 (a=0x80000003,
  DB_TRX_ID=0x000000000000,
  DB_ROLL_PTR=0x80000000000000,
  b=0x7ffffffd)
-header=0x030008030000 (a=0x73757072656d756d00)
+header=0x040008030000 (a=0x73757072656d756d00)
 UNLOCK TABLES;
 SELECT * FROM t1;
-a	b
-1	2
-3	-3
+a	b	c
+1	2	NULL
+3	-3	NULL
 DROP TABLE t1;
 SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;
diff --git a/mysql-test/suite/innodb/r/instant_alter.result b/mysql-test/suite/innodb/r/instant_alter.result
index 1580ba29717..a70a3d077e0 100644
--- a/mysql-test/suite/innodb/r/instant_alter.result
+++ b/mysql-test/suite/innodb/r/instant_alter.result
@@ -440,6 +440,12 @@ SELECT * FROM t1;
 a	b
 a	1
 DROP TABLE t1;
+CREATE TABLE t1 (a INT, b VARCHAR(8), PRIMARY KEY(b,a)) ENGINE=InnoDB ROW_FORMAT=REDUNDANT;
+INSERT INTO t1 VALUES (1,'foo');
+ALTER TABLE t1 ADD COLUMN c INT;
+UPDATE t1 SET c = 1;
+UPDATE t1 SET c = 2;
+DROP TABLE t1;
 CREATE TABLE t1
 (id INT PRIMARY KEY, c2 INT UNIQUE,
 c3 POINT NOT NULL DEFAULT ST_GeomFromText('POINT(3 4)'),
@@ -826,6 +832,12 @@ SELECT * FROM t1;
 a	b
 a	1
 DROP TABLE t1;
+CREATE TABLE t1 (a INT, b VARCHAR(8), PRIMARY KEY(b,a)) ENGINE=InnoDB ROW_FORMAT=COMPACT;
+INSERT INTO t1 VALUES (1,'foo');
+ALTER TABLE t1 ADD COLUMN c INT;
+UPDATE t1 SET c = 1;
+UPDATE t1 SET c = 2;
+DROP TABLE t1;
 CREATE TABLE t1
 (id INT PRIMARY KEY, c2 INT UNIQUE,
 c3 POINT NOT NULL DEFAULT ST_GeomFromText('POINT(3 4)'),
@@ -1212,10 +1224,16 @@ SELECT * FROM t1;
 a	b
 a	1
 DROP TABLE t1;
+CREATE TABLE t1 (a INT, b VARCHAR(8), PRIMARY KEY(b,a)) ENGINE=InnoDB ROW_FORMAT=DYNAMIC;
+INSERT INTO t1 VALUES (1,'foo');
+ALTER TABLE t1 ADD COLUMN c INT;
+UPDATE t1 SET c = 1;
+UPDATE t1 SET c = 2;
+DROP TABLE t1;
 disconnect analyze;
 SELECT variable_value-@old_instant instants
 FROM information_schema.global_status
 WHERE variable_name = 'innodb_instant_alter_column';
 instants
-36
+39
 SET GLOBAL innodb_purge_rseg_truncate_frequency= @saved_frequency;
diff --git a/mysql-test/suite/innodb/r/instant_alter_debug.result b/mysql-test/suite/innodb/r/instant_alter_debug.result
index 3aec7553ff0..bd7d538678a 100644
--- a/mysql-test/suite/innodb/r/instant_alter_debug.result
+++ b/mysql-test/suite/innodb/r/instant_alter_debug.result
@@ -35,7 +35,7 @@ ALTER TABLE t4 ADD COLUMN b INT;
 SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
 LEFT JOIN t4 ON (NUMERIC_SCALE = pk);
 COUNT(*)
-1748
+953
 SET DEBUG_SYNC='innodb_inplace_alter_table_enter SIGNAL enter WAIT_FOR delete';
 ALTER TABLE t4 ADD COLUMN c INT;
 connect  dml,localhost,root,,;