MDEV-17376 Server fails to set ADD_PK_INDEX, DROP_PK_INDEX if unique index nominated as PK

Problem:
========
Server fails to notify the engine by not setting the ADD_PK_INDEX and
DROP_PK_INDEX When there is a
 i) Change in candidate for primary key.
 ii) New candidate for primary key.

Fix:
====
Server sets the ADD_PK_INDEX and DROP_PK_INDEX while doing alter for the
above problematic case.

5 files changed, 196 insertions, 15 deletions

diff --git a/mysql-test/suite/innodb/r/alter_candidate_key.result b/mysql-test/suite/innodb/r/alter_candidate_key.result
new file mode 100644
index 00000000000..b0b8e390c7e
--- /dev/null
+++ b/mysql-test/suite/innodb/r/alter_candidate_key.result
@@ -0,0 +1,107 @@
+CREATE TABLE t1 (f1 INT NOT NULL, f2 INT NOT NULL,
+UNIQUE KEY uidx2(f1,f2),
+UNIQUE KEY uidx1(f2)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1, 1);
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) NOT NULL,
+  `f2` int(11) NOT NULL,
+  UNIQUE KEY `uidx2` (`f1`,`f2`),
+  UNIQUE KEY `uidx1` (`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+SET DEBUG_SYNC = 'innodb_inplace_alter_table_enter
+		  SIGNAL conc_dml WAIT_FOR go_ahead';
+ALTER TABLE t1 CHANGE COLUMN f1 f11 INT, ALGORITHM=INPLACE;
+SET DEBUG_SYNC = 'now WAIT_FOR conc_dml';
+DELETE FROM t1;
+SET DEBUG_SYNC = 'now SIGNAL go_ahead';
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f11` int(11) DEFAULT NULL,
+  `f2` int(11) NOT NULL,
+  UNIQUE KEY `uidx1` (`f2`),
+  UNIQUE KEY `uidx2` (`f11`,`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+CHECK TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+DROP TABLE t1;
+CREATE TABLE t1(f1 INT, f2 INT,
+PRIMARY KEY(f1, f2),
+UNIQUE INDEX uidx2 (f1, f2),
+UNIQUE INDEX uidx1 (f2))ENGINE=InnoDB;
+ALTER TABLE t1 DROP PRIMARY KEY;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) NOT NULL DEFAULT '0',
+  `f2` int(11) NOT NULL DEFAULT '0',
+  UNIQUE KEY `uidx2` (`f1`,`f2`),
+  UNIQUE KEY `uidx1` (`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+SET DEBUG_SYNC = 'innodb_inplace_alter_table_enter
+		  SIGNAL conc_dml WAIT_FOR go_ahead';
+ALTER TABLE t1 CHANGE COLUMN f1 f11 INT, ALGORITHM=INPLACE;
+SET DEBUG_SYNC = 'now WAIT_FOR conc_dml';
+INSERT INTO t1 VALUES(1, 1), (1, 1);
+ERROR 23000: Duplicate entry '1-1' for key 'uidx2'
+SET DEBUG_SYNC = 'now SIGNAL go_ahead';
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f11` int(11) DEFAULT NULL,
+  `f2` int(11) NOT NULL DEFAULT '0',
+  UNIQUE KEY `uidx1` (`f2`),
+  UNIQUE KEY `uidx2` (`f11`,`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+CHECK TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+DROP TABLE t1;
+SET SQL_MODE= strict_trans_tables;
+CREATE TABLE t1(a INT UNIQUE) ENGINE=InnoDB;
+SET DEBUG_SYNC='row_log_table_apply1_before SIGNAL dml WAIT_FOR dml_done';
+ALTER TABLE t1 MODIFY COLUMN a INT NOT NULL;
+SET DEBUG_SYNC='now WAIT_FOR dml';
+BEGIN;
+INSERT INTO t1 SET a=NULL;
+ROLLBACK;
+set DEBUG_SYNC='now SIGNAL dml_done';
+ERROR 22004: Invalid use of NULL value
+DROP TABLE t1;
+SET DEBUG_SYNC="RESET";
+SET SQL_MODE=DEFAULT;
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL, PRIMARY KEY(f1, f2),
+UNIQUE KEY(f2))ENGINE=InnoDB;
+ALTER TABLE t1 DROP PRIMARY KEY;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) NOT NULL,
+  `f2` int(11) NOT NULL,
+  UNIQUE KEY `f2` (`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+DROP TABLE t1;
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+UNIQUE KEY(f2), UNIQUE KEY(f2))ENGINE=InnoDB;
+Warnings:
+Note	1831	Duplicate index `f2_2`. This is deprecated and will be disallowed in a future release.
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) NOT NULL,
+  `f2` int(11) NOT NULL,
+  UNIQUE KEY `f2` (`f2`),
+  UNIQUE KEY `f2_2` (`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+ALTER TABLE t1 DROP INDEX f2, ALGORITHM=INPLACE;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) NOT NULL,
+  `f2` int(11) NOT NULL,
+  UNIQUE KEY `f2_2` (`f2`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+DROP TABLE t1;
diff --git a/mysql-test/suite/innodb/r/innodb-table-online.result b/mysql-test/suite/innodb/r/innodb-table-online.result
index eb55ba57e36..0a8d1c2fefb 100644
--- a/mysql-test/suite/innodb/r/innodb-table-online.result
+++ b/mysql-test/suite/innodb/r/innodb-table-online.result
@@ -85,17 +85,6 @@ t1	CREATE TABLE `t1` (
   UNIQUE KEY `c2` (`c2`),
   UNIQUE KEY `c2_2` (`c2`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=COMPACT
-ALTER TABLE t1 DROP INDEX c2, ALGORITHM = INPLACE;
-ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: Dropping a primary key is not allowed without also adding a new primary key. Try ALGORITHM=COPY.
-SHOW CREATE TABLE t1;
-Table	Create Table
-t1	CREATE TABLE `t1` (
-  `c1` int(11) NOT NULL,
-  `c2` int(11) NOT NULL,
-  `c3` text NOT NULL,
-  UNIQUE KEY `c2` (`c2`),
-  UNIQUE KEY `c2_2` (`c2`)
-) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=COMPACT
 ALTER TABLE t1 DROP INDEX c2, ADD PRIMARY KEY(c1);
 # session default
 SET DEBUG_SYNC = 'now WAIT_FOR scanned';
diff --git a/mysql-test/suite/innodb/t/alter_candidate_key.test b/mysql-test/suite/innodb/t/alter_candidate_key.test
new file mode 100644
index 00000000000..7429cd89a1a
--- /dev/null
+++ b/mysql-test/suite/innodb/t/alter_candidate_key.test
@@ -0,0 +1,72 @@
+--source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+
+CREATE TABLE t1 (f1 INT NOT NULL, f2 INT NOT NULL,
+		 UNIQUE KEY uidx2(f1,f2),
+		 UNIQUE KEY uidx1(f2)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1, 1);
+SHOW CREATE TABLE t1;
+SET DEBUG_SYNC = 'innodb_inplace_alter_table_enter
+		  SIGNAL conc_dml WAIT_FOR go_ahead';
+--send ALTER TABLE t1 CHANGE COLUMN f1 f11 INT, ALGORITHM=INPLACE
+connect (con1,localhost,root,,);
+SET DEBUG_SYNC = 'now WAIT_FOR conc_dml';
+DELETE FROM t1;
+SET DEBUG_SYNC = 'now SIGNAL go_ahead';
+connection default;
+reap;
+SHOW CREATE TABLE t1;
+CHECK TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT, f2 INT,
+		PRIMARY KEY(f1, f2),
+		UNIQUE INDEX uidx2 (f1, f2),
+		UNIQUE INDEX uidx1 (f2))ENGINE=InnoDB;
+ALTER TABLE t1 DROP PRIMARY KEY;
+SHOW CREATE TABLE t1;
+SET DEBUG_SYNC = 'innodb_inplace_alter_table_enter
+		  SIGNAL conc_dml WAIT_FOR go_ahead';
+--send ALTER TABLE t1 CHANGE COLUMN f1 f11 INT, ALGORITHM=INPLACE
+connection con1;
+SET DEBUG_SYNC = 'now WAIT_FOR conc_dml';
+--error ER_DUP_ENTRY
+INSERT INTO t1 VALUES(1, 1), (1, 1);
+SET DEBUG_SYNC = 'now SIGNAL go_ahead';
+connection default;
+reap;
+SHOW CREATE TABLE t1;
+CHECK TABLE t1;
+DROP TABLE t1;
+
+SET SQL_MODE= strict_trans_tables;
+CREATE TABLE t1(a INT UNIQUE) ENGINE=InnoDB;
+SET DEBUG_SYNC='row_log_table_apply1_before SIGNAL dml WAIT_FOR dml_done';
+--send ALTER TABLE t1 MODIFY COLUMN a INT NOT NULL
+connection con1;
+SET DEBUG_SYNC='now WAIT_FOR dml';
+BEGIN;
+INSERT INTO t1 SET a=NULL;
+ROLLBACK;
+set DEBUG_SYNC='now SIGNAL dml_done';
+connection default;
+--error ER_INVALID_USE_OF_NULL
+reap;
+DROP TABLE t1;
+disconnect con1;
+SET DEBUG_SYNC="RESET";
+SET SQL_MODE=DEFAULT;
+
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL, PRIMARY KEY(f1, f2),
+		UNIQUE KEY(f2))ENGINE=InnoDB;
+ALTER TABLE t1 DROP PRIMARY KEY;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+		UNIQUE KEY(f2), UNIQUE KEY(f2))ENGINE=InnoDB;
+SHOW CREATE TABLE t1;
+ALTER TABLE t1 DROP INDEX f2, ALGORITHM=INPLACE;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
diff --git a/mysql-test/suite/innodb/t/innodb-table-online.test b/mysql-test/suite/innodb/t/innodb-table-online.test
index 4e9f2f13344..b0711412a52 100644
--- a/mysql-test/suite/innodb/t/innodb-table-online.test
+++ b/mysql-test/suite/innodb/t/innodb-table-online.test
@@ -101,10 +101,6 @@ ALTER TABLE t1 ADD UNIQUE INDEX(c2),
 LOCK = EXCLUSIVE, ALGORITHM = INPLACE;
 
 SHOW CREATE TABLE t1;
-# We do not support plain DROP_PK_INDEX without ADD_PK_INDEX.
---error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
-ALTER TABLE t1 DROP INDEX c2, ALGORITHM = INPLACE;
-SHOW CREATE TABLE t1;
 # Now the previous DEBUG_SYNC should kick in.
 --send
 ALTER TABLE t1 DROP INDEX c2, ADD PRIMARY KEY(c1);
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 2302026b18b..df1ff8eaf5d 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -6439,6 +6439,12 @@ static bool fill_alter_inplace_info(THD *thd,
   KEY *new_key;
   KEY *new_key_end=
     ha_alter_info->key_info_buffer + ha_alter_info->key_count;
+  /*
+    Primary key index for the new table
+  */
+  const KEY* const new_pk= (ha_alter_info->key_count > 0 &&
+                            is_candidate_key(ha_alter_info->key_info_buffer)) ?
+                           ha_alter_info->key_info_buffer : NULL;
 
   DBUG_PRINT("info", ("index count old: %d  new: %d",
                       table->s->keys, ha_alter_info->key_count));
@@ -6513,6 +6519,17 @@ static bool fill_alter_inplace_info(THD *thd,
           new_field->field->field_index != key_part->fieldnr - 1)
         goto index_changed;
     }
+
+    /*
+      Rebuild the index if following condition get satisfied:
+
+      (i) Old table doesn't have primary key, new table has it and vice-versa
+      (ii) Primary key changed to another existing index
+    */
+    if ((new_key == new_pk) !=
+        ((uint) (table_key - table->key_info) == table->s->primary_key))
+      goto index_changed;
+
     continue;
 
   index_changed: