MDEV-26137 Improve import tablespace workflow.

Allow ALTER TABLE ... IMPORT TABLESPACE without creating the table
followed by discarding the tablespace.

That is, assuming we want to import table t1 to t2, instead of

CREATE TABLE t2 LIKE t1;
ALTER TABLE t2 DISCARD TABLESPACE;
FLUSH TABLES t1 FOR EXPORT;
--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
UNLOCK TABLES;
ALTER TABLE t2 IMPORT TABLESPACE;

We can simply do

FLUSH TABLES t1 FOR EXPORT;
--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
--copy_file $MYSQLD_DATADIR/test/t1.frm $MYSQLD_DATADIR/test/t2.frm
--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
UNLOCK TABLES;
ALTER TABLE t2 IMPORT TABLESPACE;

We achieve this by creating a "stub" table in the second scenario
while opening the table, where t2 does not exist but needs to import
from t1. The "stub" table is similar to a table that is created but
then instructed to discard its tablespace.

We include tests with various row formats, encryption, with indexes
and auto-increment.
Signed-off-by: Yuchen Pei <yuchen.pei@mariadb.com>

mysql-test/suite/encryption/r/innodb_import.result

@@ -20,3 +20,22 @@ SELECT * FROM t2;
 f1	f2
 1	InnoDB
 DROP TABLE t1, t2;
+#
+# MDEV-26137 ALTER TABLE IMPORT enhancement
+#
+# with encryption and page_compressed
+CREATE TABLE t1 (a int, b varchar(50)) ENGINE=InnoDB ENCRYPTED=YES ENCRYPTION_KEY_ID=6 PAGE_COMPRESSED=1;
+INSERT INTO t1 VALUES(42, "hello");
+FLUSH TABLES t1 FOR EXPORT;
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) DEFAULT NULL,
+  `b` varchar(50) DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci `ENCRYPTED`=YES `ENCRYPTION_KEY_ID`=6 `PAGE_COMPRESSED`=1
+SELECT * FROM t2;
+a	b
+42	hello
+DROP TABLE t1, t2;

mysql-test/suite/encryption/t/innodb_import.test

@@ -21,3 +21,22 @@ ALTER TABLE t2 DROP KEY idx;
 ALTER TABLE t2 IMPORT TABLESPACE;
 SELECT * FROM t2;
 DROP TABLE t1, t2;
+
+--echo #
+--echo # MDEV-26137 ALTER TABLE IMPORT enhancement
+--echo #
+
+--echo # with encryption and page_compressed
+CREATE TABLE t1 (a int, b varchar(50)) ENGINE=InnoDB ENCRYPTED=YES ENCRYPTION_KEY_ID=6 PAGE_COMPRESSED=1;
+INSERT INTO t1 VALUES(42, "hello");
+FLUSH TABLES t1 FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
+--copy_file $MYSQLD_DATADIR/test/t1.frm $MYSQLD_DATADIR/test/t2.frm
+--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+SELECT * FROM t2;
+DROP TABLE t1, t2;
+
+# Embedded server uses absolute path, causing result mismatch in warning messages when .cfg is not copied over. Given we have tested importing without copying cfg in other tests, we don't do it here.

mysql-test/suite/innodb/include/import_begin.inc

+--source include/innodb_row_format.inc
+--source include/innodb_row_format_2.inc
+--source include/innodb_checksum_algorithm.inc
+
+--echo #
+--echo # MDEV-26137 ALTER TABLE IMPORT enhancement
+--echo #
+
+let $MYSQLD_DATADIR = `SELECT @@datadir`;
+
+--disable_query_log
+let $ROW_FORMAT_OPTION=;
+if($MTR_COMBINATION_R_REDUNDANT) {
+  let $ROW_FORMAT_OPTION= ROW_FORMAT=REDUNDANT;
+}
+if($MTR_COMBINATION_R_COMPACT) {
+  let $ROW_FORMAT_OPTION= ROW_FORMAT=COMPACT;
+}
+if($MTR_COMBINATION_R_DYNAMIC) {
+  let $ROW_FORMAT_OPTION= ROW_FORMAT=DYNAMIC;
+}
+if($MTR_COMBINATION_R_COMPRESSED) {
+  let $ROW_FORMAT_OPTION= ROW_FORMAT=COMPRESSED;
+}
+let $CREATE_OPTIONS_REGEX= /ENGINE=InnoDB.*$ROW_FORMAT_OPTION/CREATE_OPTIONS/;
+--enable_query_log
+
+--replace_regex $CREATE_OPTIONS_REGEX
+eval
+CREATE TABLE t1(a INT PRIMARY KEY DEFAULT 42) ENGINE=InnoDB $ROW_FORMAT_OPTION;
+INSERT INTO t1() VALUES();
+FLUSH TABLES t1 FOR EXPORT;

mysql-test/suite/innodb/include/import_end.inc

+--copy_file $MYSQLD_DATADIR/test/t1.frm $MYSQLD_DATADIR/test/t2.frm
+--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+--replace_regex $CREATE_OPTIONS_REGEX
+SHOW CREATE TABLE t2;
+SELECT * FROM t2;
+DROP TABLE t1, t2;

mysql-test/suite/innodb/include/innodb_row_format_2.combinations

+[r_default]
+[r_redundant]
+[r_compact]
+[r_dynamic]
+[r_compressed]

mysql-test/suite/innodb/include/innodb_row_format_2.inc

+# The goal of including this file is to add various row_format options
+# combinations (see include/innodb_row_format_2.combinations)
+
+--source include/have_innodb.inc

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

+#
+# MDEV-26137 ALTER TABLE IMPORT enhancement
+#
+CREATE TABLE t1(a INT PRIMARY KEY DEFAULT 42) CREATE_OPTIONS;
+INSERT INTO t1() VALUES();
+FLUSH TABLES t1 FOR EXPORT;
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) NOT NULL DEFAULT 42,
+  PRIMARY KEY (`a`)
+) CREATE_OPTIONS
+SELECT * FROM t2;
+a
+42
+DROP TABLE t1, t2;

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

+#
+# MDEV-26137 ALTER TABLE IMPORT enhancement
+#
+CREATE TABLE t1(a INT PRIMARY KEY DEFAULT 42) CREATE_OPTIONS;
+INSERT INTO t1() VALUES();
+FLUSH TABLES t1 FOR EXPORT;
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+Warnings:
+Warning	1810	IO Read error: (2, No such file or directory) Error opening './test/t2.cfg', will attempt to import without schema verification
+Warning	1810	IO Read error: (2, No such file or directory) Error opening './test/t2.cfg', will attempt to import without schema verification
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) NOT NULL DEFAULT 42,
+  PRIMARY KEY (`a`)
+) CREATE_OPTIONS
+SELECT * FROM t2;
+a
+42
+DROP TABLE t1, t2;

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

+#
+# MDEV-26137 ALTER TABLE IMPORT enhancement
+#
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t1` is set as discarded.');
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t2` is set as discarded.');
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t3` is set as discarded.');
+call mtr.add_suppression('InnoDB: ./test/t3.ibd: Page 0 at offset 0 looks corrupted.');
+call mtr.add_suppression("mariadbd.*: Index for table 't3' is corrupt; try to repair it");
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t3.ibd' could not be found in the doublewrite buffer.");
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t4` is set as discarded.');
+call mtr.add_suppression('InnoDB: ./test/t4.ibd: Page 0 at offset 0 looks corrupted.');
+call mtr.add_suppression("mariadbd.*: Index for table 't4' is corrupt; try to repair it");
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t4.ibd' could not be found in the doublewrite buffer.");
+# Recovery from crashes
+## t1: Creation of stub succeeds; server crashes; second import attempt succeeds
+## t2: Creation of stub succeeds; server crashes; drop table
+## t3: Creation of stub succeeds; server crashes; ibd corrupted; second import attempt fails; drop table
+## t4: Did not copy .cfg; creation of stub succeeds; server crashes; ibd corrupted; second import attempt fails; drop table
+CREATE TABLE t (a int) ENGINE=InnoDB;
+INSERT INTO t VALUES(42);
+FLUSH TABLES t FOR EXPORT;
+UNLOCK TABLES;
+connect  hang1,localhost,root;
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+ALTER TABLE t1 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+connect  hang2,localhost,root;
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+ALTER TABLE t2 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+connect  hang3,localhost,root;
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+ALTER TABLE t3 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+connect  hang4,localhost,root;
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+ALTER TABLE t4 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+# corrupting the 0th page
+# Restart mysqld after the crash and reconnect.
+# restart
+ALTER TABLE t1 IMPORT TABLESPACE;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+SELECT * FROM t1;
+a
+42
+ALTER TABLE t3 IMPORT TABLESPACE;
+ERROR HY000: Internal error: Error importing tablespace for table `test`.`t3` : Data structure corruption
+ALTER TABLE t4 IMPORT TABLESPACE;
+ERROR HY000: Schema mismatch (Expected FSP_SPACE_FLAGS=0x15, .ibd file contains 0x1010115.)
+DROP TABLE t, t1, t2, t3, t4;
+# Recovery from corruption only, no server restart
+## t5: Recovery from corruption, with cfg
+## t6: Recovery from corruption, without cfg
+call mtr.add_suppression('InnoDB: ./test/t5.ibd: Page 0 at offset 0 looks corrupted.');
+call mtr.add_suppression("mariadbd.*: Index for table 't5' is corrupt; try to repair it");
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t5.ibd' could not be found in the doublewrite buffer.");
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t6.ibd' could not be found in the doublewrite buffer.");
+call mtr.add_suppression("mariadbd.*: Index for table 't6' is corrupt; try to repair it");
+CREATE TABLE t (a int) ENGINE=InnoDB;
+INSERT INTO t VALUES(42);
+FLUSH TABLES t FOR EXPORT;
+UNLOCK TABLES;
+# corrupting the 0th page
+ALTER TABLE t5 IMPORT TABLESPACE;
+ERROR HY000: Internal error: Error importing tablespace for table `test`.`t5` : Data structure corruption
+ALTER TABLE t6 IMPORT TABLESPACE;
+ERROR HY000: Schema mismatch (Expected FSP_SPACE_FLAGS=0x15, .ibd file contains 0x1010115.)
+DROP TABLE t, t5, t6;

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

+#
+# MDEV-26137 ALTER TABLE IMPORT enhancement
+#
+# drop t1 before importing t2
+CREATE TABLE t1 (a int) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(42);
+FLUSH TABLES t1 FOR EXPORT;
+UNLOCK TABLES;
+DROP TABLE t1;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+SELECT * FROM t2;
+a
+42
+DROP TABLE t2;
+# created t2 but did not discard tablespace
+CREATE TABLE t1 (a int) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(42);
+CREATE TABLE t2 LIKE t1;
+FLUSH TABLES t1 FOR EXPORT;
+UNLOCK TABLES;
+DROP TABLE t1;
+call mtr.add_suppression("InnoDB: Unable to import tablespace");
+ALTER TABLE t2 IMPORT TABLESPACE;
+ERROR HY000: Tablespace for table 'test/t2' exists. Please DISCARD the tablespace before IMPORT
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+SELECT * FROM t2;
+a
+DROP TABLE t2;
+# attempt to import when there's no tablespace
+ALTER TABLE t2 IMPORT TABLESPACE;
+ERROR 42S02: Table 'test.t2' doesn't exist
+# with index
+CREATE TABLE t1 (a int, b varchar(50)) ENGINE=InnoDB;
+CREATE UNIQUE INDEX ai ON t1 (a);
+INSERT INTO t1 VALUES(42, "hello");
+FLUSH TABLES t1 FOR EXPORT;
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) DEFAULT NULL,
+  `b` varchar(50) DEFAULT NULL,
+  UNIQUE KEY `ai` (`a`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+SELECT * FROM t2;
+a	b
+42	hello
+SHOW INDEX FROM t1;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
+t1	0	ai	1	a	A	1	NULL	NULL	YES	BTREE			NO
+SHOW INDEX FROM t2;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
+t2	0	ai	1	a	A	1	NULL	NULL	YES	BTREE			NO
+DROP TABLE t1, t2;
+# with virtual column index
+CREATE TABLE t1 (a int, b int as (a * a)) ENGINE=InnoDB;
+CREATE UNIQUE INDEX ai ON t1 (b);
+INSERT INTO t1 VALUES(42, default);
+FLUSH TABLES t1 FOR EXPORT;
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) GENERATED ALWAYS AS (`a` * `a`) VIRTUAL,
+  UNIQUE KEY `ai` (`b`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+SELECT * FROM t2;
+a	b
+42	1764
+SELECT b FROM t2 USE INDEX (ai);
+b
+1764
+SHOW INDEX FROM t1;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
+t1	0	ai	1	b	A	1	NULL	NULL	YES	BTREE			NO
+SHOW INDEX FROM t2;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
+t2	0	ai	1	b	A	1	NULL	NULL	YES	BTREE			NO
+CHECK TABLE t2 EXTENDED;
+Table	Op	Msg_type	Msg_text
+test.t2	check	status	OK
+DROP TABLE t1, t2;
+# with auto_increment
+CREATE TABLE t1 (id INT PRIMARY KEY AUTO_INCREMENT, i2 INT, i1 INT)ENGINE=INNODB;
+INSERT INTO t1 (i2) SELECT 4 FROM seq_1_to_1024;
+FLUSH TABLE t1 FOR EXPORT;
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+CHECK TABLE t2 EXTENDED;
+Table	Op	Msg_type	Msg_text
+test.t2	check	status	OK
+DROP TABLE t2, t1;

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

+--source include/import_begin.inc
+--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
+--source include/import_end.inc

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

+# embedded server uses absolute path, causing result mismatch in warning messages
+--source include/not_embedded.inc
+--source include/import_begin.inc
+--source include/import_end.inc

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

+--source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/not_embedded.inc
+
+--echo #
+--echo # MDEV-26137 ALTER TABLE IMPORT enhancement
+--echo #
+
+let MYSQLD_DATADIR = `SELECT @@datadir`;
+let INNODB_PAGE_SIZE=`select @@innodb_page_size`;
+
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t1` is set as discarded.');
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t2` is set as discarded.');
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t3` is set as discarded.');
+call mtr.add_suppression('InnoDB: ./test/t3.ibd: Page 0 at offset 0 looks corrupted.');
+call mtr.add_suppression("mariadbd.*: Index for table 't3' is corrupt; try to repair it");
+# In Windows etc.
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t3.ibd' could not be found in the doublewrite buffer.");
+call mtr.add_suppression('InnoDB: Tablespace for table `test`.`t4` is set as discarded.');
+call mtr.add_suppression('InnoDB: ./test/t4.ibd: Page 0 at offset 0 looks corrupted.');
+call mtr.add_suppression("mariadbd.*: Index for table 't4' is corrupt; try to repair it");
+# In Windows etc.
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t4.ibd' could not be found in the doublewrite buffer.");
+
+--echo # Recovery from crashes
+--echo ## t1: Creation of stub succeeds; server crashes; second import attempt succeeds
+--echo ## t2: Creation of stub succeeds; server crashes; drop table
+--echo ## t3: Creation of stub succeeds; server crashes; ibd corrupted; second import attempt fails; drop table
+--echo ## t4: Did not copy .cfg; creation of stub succeeds; server crashes; ibd corrupted; second import attempt fails; drop table
+CREATE TABLE t (a int) ENGINE=InnoDB;
+INSERT INTO t VALUES(42);
+FLUSH TABLES t FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t.cfg $MYSQLD_DATADIR/test/t1.cfg
+--copy_file $MYSQLD_DATADIR/test/t.frm $MYSQLD_DATADIR/test/t1.frm
+--copy_file $MYSQLD_DATADIR/test/t.ibd $MYSQLD_DATADIR/test/t1.ibd
+--copy_file $MYSQLD_DATADIR/test/t.cfg $MYSQLD_DATADIR/test/t2.cfg
+--copy_file $MYSQLD_DATADIR/test/t.frm $MYSQLD_DATADIR/test/t2.frm
+--copy_file $MYSQLD_DATADIR/test/t.ibd $MYSQLD_DATADIR/test/t2.ibd
+--copy_file $MYSQLD_DATADIR/test/t.cfg $MYSQLD_DATADIR/test/t3.cfg
+--copy_file $MYSQLD_DATADIR/test/t.frm $MYSQLD_DATADIR/test/t3.frm
+--copy_file $MYSQLD_DATADIR/test/t.ibd $MYSQLD_DATADIR/test/t3.ibd
+--copy_file $MYSQLD_DATADIR/test/t.frm $MYSQLD_DATADIR/test/t4.frm
+--copy_file $MYSQLD_DATADIR/test/t.ibd $MYSQLD_DATADIR/test/t4.ibd
+UNLOCK TABLES;
+
+connect (hang1,localhost,root);
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+send ALTER TABLE t1 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+
+connect (hang2,localhost,root);
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+send ALTER TABLE t2 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+
+connect (hang3,localhost,root);
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+send ALTER TABLE t3 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+
+connect (hang4,localhost,root);
+SET DEBUG_SYNC='ib_after_create_stub_for_import SIGNAL hung WAIT_FOR ever';
+send ALTER TABLE t4 IMPORT TABLESPACE;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR hung';
+
+let $shutdown_timeout=0;
+--source include/shutdown_mysqld.inc
+
+--echo # corrupting the 0th page
+perl;
+my $ps = $ENV{INNODB_PAGE_SIZE};
+
+@tables= ('t3', 't4');
+foreach $table (@tables) {
+  my $file = "$ENV{MYSQLD_DATADIR}/test/$table.ibd";
+  open(FILE, "+<$file") || die "Unable to open $file";
+  binmode FILE;
+  sysseek(FILE, 0, 0) || die "Unable to seek $file\n";
+  die "Unable to read $file" unless sysread(FILE, $page, $ps) == $ps;
+  # Replace all NUL bytes with SOH bytes.
+  $page =~ tr/\x0/\x1/;
+  sysseek(FILE, 0, 0) || die "Unable to seek $file\n";
+  syswrite(FILE, $page, $ps)==$ps || die "Unable to write $file\n";
+  close FILE or die "close";
+}
+EOF
+
+--echo # Restart mysqld after the crash and reconnect.
+--source include/start_mysqld.inc
+
+ALTER TABLE t1 IMPORT TABLESPACE;
+SHOW CREATE TABLE t1;
+SELECT * FROM t1;
+
+--error ER_INTERNAL_ERROR
+ALTER TABLE t3 IMPORT TABLESPACE;
+
+--error ER_TABLE_SCHEMA_MISMATCH
+ALTER TABLE t4 IMPORT TABLESPACE;
+
+DROP TABLE t, t1, t2, t3, t4;
+
+--echo # Recovery from corruption only, no server restart
+--echo ## t5: Recovery from corruption, with cfg
+--echo ## t6: Recovery from corruption, without cfg
+call mtr.add_suppression('InnoDB: ./test/t5.ibd: Page 0 at offset 0 looks corrupted.');
+call mtr.add_suppression("mariadbd.*: Index for table 't5' is corrupt; try to repair it");
+# In Windows etc.
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t5.ibd' could not be found in the doublewrite buffer.");
+# In Windows etc.
+call mtr.add_suppression("InnoDB: Corrupted page \\[page id: space=.*, page number=0\\] of datafile './test/t6.ibd' could not be found in the doublewrite buffer.");
+call mtr.add_suppression("mariadbd.*: Index for table 't6' is corrupt; try to repair it");
+
+CREATE TABLE t (a int) ENGINE=InnoDB;
+INSERT INTO t VALUES(42);
+FLUSH TABLES t FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t.cfg $MYSQLD_DATADIR/test/t5.cfg
+--copy_file $MYSQLD_DATADIR/test/t.frm $MYSQLD_DATADIR/test/t5.frm
+--copy_file $MYSQLD_DATADIR/test/t.ibd $MYSQLD_DATADIR/test/t5.ibd
+--copy_file $MYSQLD_DATADIR/test/t.frm $MYSQLD_DATADIR/test/t6.frm
+--copy_file $MYSQLD_DATADIR/test/t.ibd $MYSQLD_DATADIR/test/t6.ibd
+UNLOCK TABLES;
+
+--echo # corrupting the 0th page
+perl;
+my $ps = $ENV{INNODB_PAGE_SIZE};
+
+@tables= ('t5', 't6');
+foreach $table (@tables) {
+  my $file = "$ENV{MYSQLD_DATADIR}/test/$table.ibd";
+  open(FILE, "+<$file") || die "Unable to open $file";
+  binmode FILE;
+  sysseek(FILE, 0, 0) || die "Unable to seek $file\n";
+  die "Unable to read $file" unless sysread(FILE, $page, $ps) == $ps;
+  # Replace all NUL bytes with SOH bytes.
+  $page =~ tr/\x0/\x1/;
+  sysseek(FILE, 0, 0) || die "Unable to seek $file\n";
+  syswrite(FILE, $page, $ps)==$ps || die "Unable to write $file\n";
+  close FILE or die "close";
+}
+EOF
+
+--error ER_INTERNAL_ERROR
+ALTER TABLE t5 IMPORT TABLESPACE;
+
+--error ER_TABLE_SCHEMA_MISMATCH
+ALTER TABLE t6 IMPORT TABLESPACE;
+
+DROP TABLE t, t5, t6;

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

+--source include/have_innodb.inc
+--source include/have_sequence.inc
+let $MYSQLD_DATADIR = `SELECT @@datadir`;
+
+--echo #
+--echo # MDEV-26137 ALTER TABLE IMPORT enhancement
+--echo #
+
+--echo # drop t1 before importing t2
+CREATE TABLE t1 (a int) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(42);
+FLUSH TABLES t1 FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
+--copy_file $MYSQLD_DATADIR/test/t1.frm $MYSQLD_DATADIR/test/t2.frm
+--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
+UNLOCK TABLES;
+DROP TABLE t1;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+SELECT * FROM t2;
+DROP TABLE t2;
+
+--echo # created t2 but did not discard tablespace
+CREATE TABLE t1 (a int) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(42);
+CREATE TABLE t2 LIKE t1;
+FLUSH TABLES t1 FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
+UNLOCK TABLES;
+DROP TABLE t1;
+call mtr.add_suppression("InnoDB: Unable to import tablespace");
+--error ER_TABLESPACE_EXISTS
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+SELECT * FROM t2;
+DROP TABLE t2;
+
+--echo # attempt to import when there's no tablespace
+--error ER_NO_SUCH_TABLE
+ALTER TABLE t2 IMPORT TABLESPACE;
+
+--echo # with index
+CREATE TABLE t1 (a int, b varchar(50)) ENGINE=InnoDB;
+CREATE UNIQUE INDEX ai ON t1 (a);
+INSERT INTO t1 VALUES(42, "hello");
+FLUSH TABLES t1 FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
+--copy_file $MYSQLD_DATADIR/test/t1.frm $MYSQLD_DATADIR/test/t2.frm
+--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+SELECT * FROM t2;
+SHOW INDEX FROM t1;
+SHOW INDEX FROM t2;
+DROP TABLE t1, t2;
+
+--echo # with virtual column index
+CREATE TABLE t1 (a int, b int as (a * a)) ENGINE=InnoDB;
+CREATE UNIQUE INDEX ai ON t1 (b);
+INSERT INTO t1 VALUES(42, default);
+FLUSH TABLES t1 FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
+--copy_file $MYSQLD_DATADIR/test/t1.frm $MYSQLD_DATADIR/test/t2.frm
+--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+SHOW CREATE TABLE t2;
+SELECT * FROM t2;
+SELECT b FROM t2 USE INDEX (ai);
+SHOW INDEX FROM t1;
+SHOW INDEX FROM t2;
+CHECK TABLE t2 EXTENDED;
+DROP TABLE t1, t2;
+
+--echo # with auto_increment
+CREATE TABLE t1 (id INT PRIMARY KEY AUTO_INCREMENT, i2 INT, i1 INT)ENGINE=INNODB;
+INSERT INTO t1 (i2) SELECT 4 FROM seq_1_to_1024;
+FLUSH TABLE t1 FOR EXPORT;
+--copy_file $MYSQLD_DATADIR/test/t1.frm $MYSQLD_DATADIR/test/t2.frm
+--copy_file $MYSQLD_DATADIR/test/t1.ibd $MYSQLD_DATADIR/test/t2.ibd
+--copy_file $MYSQLD_DATADIR/test/t1.cfg $MYSQLD_DATADIR/test/t2.cfg
+UNLOCK TABLES;
+ALTER TABLE t2 IMPORT TABLESPACE;
+CHECK TABLE t2 EXTENDED;
+DROP TABLE t2, t1;

sql/sql_yacc.yy

@@ -7212,6 +7212,7 @@ alter_commands:
             Lex->m_sql_cmd= new (thd->mem_root)
               Sql_cmd_discard_import_tablespace(
                 Sql_cmd_discard_import_tablespace::IMPORT_TABLESPACE);
+            Lex->create_info.add(DDL_options_st::OPT_IMPORT_TABLESPACE);
             if (unlikely(Lex->m_sql_cmd == NULL))
               MYSQL_YYABORT;
           }

sql/structs.h

@@ -537,7 +537,8 @@ struct DDL_options_st
     OPT_OR_REPLACE_SLAVE_GENERATED= 32,// REPLACE was added on slave, it was
                                        // not in the original query on master.
     OPT_IF_EXISTS= 64,
-    OPT_CREATE_SELECT= 128             // CREATE ... SELECT
+    OPT_CREATE_SELECT= 128,             // CREATE ... SELECT
+    OPT_IMPORT_TABLESPACE= 256      // ALTER ... IMPORT TABLESPACE
   };
 
 private:
@@ -566,6 +567,7 @@ struct DDL_options_st
   bool like() const { return m_options & OPT_LIKE; }
   bool if_exists() const { return m_options & OPT_IF_EXISTS; }
   bool is_create_select() const { return m_options & OPT_CREATE_SELECT; }
+  bool import_tablespace() const { return m_options & OPT_IMPORT_TABLESPACE; }
 
   void add(const DDL_options_st::Options other)
   {

storage/innobase/handler/ha_innodb.cc

@@ -5225,7 +5225,8 @@ create_table_info_t::create_table_info_t(
 	  m_create_info(create_info),
 	  m_table_name(table_name), m_table(NULL),
 	  m_remote_path(remote_path),
-	  m_innodb_file_per_table(file_per_table)
+	  m_innodb_file_per_table(file_per_table),
+	  m_creating_stub(thd_ddl_options(thd)->import_tablespace())
 {
 }
 
@@ -5847,8 +5848,22 @@ ha_innobase::open(const char* name, int, uint)
 
 	DEBUG_SYNC(thd, "ib_open_after_dict_open");
 
-	if (NULL == ib_table) {
-
+	if (UNIV_LIKELY(ib_table != nullptr)) {
+	} else if (thd_ddl_options(thd)->import_tablespace()) {
+		/* If the table does not exist and we are trying to
+		import, create a "stub" table similar to the effects
+		of CREATE TABLE followed by ALTER TABLE ... DISCARD
+		TABLESPACE. */
+
+		HA_CREATE_INFO create_info;
+		if (int err = prepare_create_stub_for_import(thd, norm_name,
+							     create_info))
+			DBUG_RETURN(err);
+		create(norm_name, table, &create_info, true, nullptr);
+		DEBUG_SYNC(thd, "ib_after_create_stub_for_import");
+		ib_table = open_dict_table(name, norm_name, is_part,
+					   DICT_ERR_IGNORE_FK_NOKEY);
+	} else {
 		if (is_part) {
 			sql_print_error("Failed to open table %s.\n",
 					norm_name);
@@ -10571,6 +10586,10 @@ create_table_info_t::create_table_def()
 				      ? doc_id_col : n_cols - num_v;
 	}
 
+	/* Assume the tablespace is not available until we are able to
+	import it.*/
+	table->file_unreadable = m_creating_stub;
+
 	if (DICT_TF_HAS_DATA_DIR(m_flags)) {
 		ut_a(strlen(m_remote_path));
 
@@ -11584,6 +11603,10 @@ bool create_table_info_t::innobase_table_flags()
 		}
 	}
 
+	/* If we are trying to import a tablespace, mark tablespace as
+	discarded. */
+	m_flags2 |= ulint{m_creating_stub} << DICT_TF2_POS_DISCARDED;
+
 	row_type = m_create_info->row_type;
 
 	if (zip_ssize && zip_allowed) {
@@ -12732,6 +12755,7 @@ int create_table_info_t::create_table(bool create_fk)
 		dict_table_get_all_fts_indexes(m_table, fts->indexes);
 	}
 
+	create_fk&= !m_creating_stub;
 	dberr_t err = create_fk ? create_foreign_keys() : DB_SUCCESS;
 
 	if (err == DB_SUCCESS) {
@@ -13136,6 +13160,9 @@ ha_innobase::create(const char *name, TABLE *form, HA_CREATE_INFO *create_info,
   }
 
   if (!error)
+    /* We can't possibly have foreign key information when creating a
+    stub table for importing .frm / .cfg / .ibd because it is not
+    stored in any of these files. */
     error= info.create_table(own_trx);
 
   if (own_trx || (info.flags2() & DICT_TF2_TEMPORARY))
@@ -13158,7 +13185,11 @@ ha_innobase::create(const char *name, TABLE *form, HA_CREATE_INFO *create_info,
 
       if (!error)
       {
-        dict_stats_update(info.table(), DICT_STATS_EMPTY_TABLE);
+        /* Skip stats update when creating a stub table for importing,
+        as it is not needed and would report error due to the table
+        not being readable yet. */
+        if (!info.creating_stub())
+          dict_stats_update(info.table(), DICT_STATS_EMPTY_TABLE);
         if (!info.table()->is_temporary())
           log_write_up_to(trx->commit_lsn, true);
         info.table()->release();

storage/innobase/handler/ha_innodb.h

@@ -701,6 +701,8 @@ class create_table_info_t
 	ulint flags2() const
 	{ return(m_flags2); }
 
+	bool creating_stub() const { return UNIV_UNLIKELY(m_creating_stub); }
+
 	/** Get trx. */
 	trx_t* trx() const
 	{ return(m_trx); }
@@ -767,6 +769,9 @@ class create_table_info_t
 
 	/** Table flags2 */
 	ulint		m_flags2;
+
+	/** Whether we are creating a stub table for importing. */
+	const bool	m_creating_stub;
 };
 
 /**

storage/innobase/include/dict0mem.h

@@ -264,7 +264,8 @@ use its own tablespace instead of the system tablespace. */
 #define DICT_TF2_USE_FILE_PER_TABLE	16U
 
 /** Set when we discard/detach the tablespace */
-#define DICT_TF2_DISCARDED		32U
+constexpr ulint DICT_TF2_POS_DISCARDED= 5;
+constexpr ulint DICT_TF2_DISCARDED= 1U << DICT_TF2_POS_DISCARDED;
 
 /** This bit is set if all aux table names (both common tables and
 index tables) of a FTS table are in HEX format. */
@@ -2097,8 +2098,9 @@ struct dict_table_t {
 	process of altering partitions */
 	unsigned                                skip_alter_undo:1;
 
-	/*!< whether this is in a single-table tablespace and the .ibd
-	file is missing or page decryption failed and page is corrupted */
+	/** whether this is in a single-table tablespace and the .ibd file
+	is believed to be missing or page decryption failed and page is
+	corrupted */
 	unsigned				file_unreadable:1;
 
 	/** TRUE if the table object has been added to the dictionary cache. */

storage/innobase/include/row0import.h

@@ -33,6 +33,7 @@ Created 2012-02-08 by Sunny Bains
 struct trx_t;
 struct dict_table_t;
 struct row_prebuilt_t;
+struct HA_CREATE_INFO;
 
 /*****************************************************************//**
 Imports a tablespace. The space id in the .ibd file must match the space id
@@ -64,4 +65,13 @@ dberr_t
 row_import_update_index_root(trx_t* trx, dict_table_t* table, bool reset)
 	MY_ATTRIBUTE((nonnull, warn_unused_result));
 
+/** Prepare the create info to create a new stub table for import.
+@param thd          Connection
+@param name         Table name, format: "db/table_name".
+@param create_info  The create info for creating a stub.
+@return ER_ error code
+@retval 0 on success */
+int prepare_create_stub_for_import(THD *thd, const char *name,
+                                   HA_CREATE_INFO& create_info);
+
 #endif /* row0import_h */