Merge 10.4 into 10.5

mysql-test/main/mysql_binary_zero_insert.result

@@ -32,8 +32,8 @@ COUNT(*)=8
 # Note: We only look for 00 because the 5c only served as an escape
 #       in parsing.
 #
-# MYSQL_DUMP test tb --hex-blob | grep INSERT > MYSQL_TMP_DIR/dump.sql
+# MYSQL_DUMP test tb --hex-blob > MYSQL_TMP_DIR/dump.sql
-FOUND 10 /00/ in dump.sql
+FOUND 8 /\([0-9]+,0x([1-9][0-9])*00([1-9][0-9])*\)/ in dump.sql
 #
 # Ensure data consistency on mysqlbinlog replay
 #

mysql-test/main/mysql_binary_zero_insert.test

@@ -114,9 +114,9 @@ SELECT COUNT(*)=8 from tb;
 --echo # Note: We only look for 00 because the 5c only served as an escape
 --echo #       in parsing.
 --echo #
---echo # MYSQL_DUMP test tb --hex-blob | grep INSERT > MYSQL_TMP_DIR/dump.sql
+--echo # MYSQL_DUMP test tb --hex-blob > MYSQL_TMP_DIR/dump.sql
---exec $MYSQL_DUMP test tb --hex-blob | grep INSERT > $MYSQL_TMP_DIR/dump.sql
+--exec $MYSQL_DUMP test tb --hex-blob > $MYSQL_TMP_DIR/dump.sql
---let SEARCH_PATTERN= 00
+--let SEARCH_PATTERN= \([0-9]+,0x([1-9][0-9])*00([1-9][0-9])*\)
 --let SEARCH_FILE= $MYSQL_TMP_DIR/dump.sql
 --source include/search_pattern_in_file.inc
 

mysql-test/suite/gcol/r/virtual_index_drop.result

@@ -25,6 +25,7 @@ t1	CREATE TABLE `t1` (
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 DROP TABLE t1;
 CREATE TABLE t1(f1 INT, f2 INT AS (f1) VIRTUAL)ENGINE=InnoDB;
+INSERT INTO t1(f1) VALUES(1);
 SET DEBUG_DBUG="+d,create_index_fail";
 SET DEBUG_SYNC="innodb_inplace_alter_table_enter SIGNAL con1_go WAIT_FOR alter_signal";
 ALTER TABLE t1 ADD COLUMN f3 INT AS (f1) VIRTUAL, ADD INDEX(f2, f3);
@@ -33,6 +34,7 @@ SET DEBUG_SYNC="now WAIT_FOR con1_go";
 BEGIN;
 SELECT * FROM t1;
 f1	f2
+1	1
 SET DEBUG_SYNC="now SIGNAL alter_signal";
 connection default;
 ERROR 23000: Duplicate entry '' for key '*UNKNOWN*'
@@ -47,6 +49,7 @@ t1	CREATE TABLE `t1` (
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 DROP TABLE t1;
 CREATE TABLE t1(f1 INT, f2 INT AS (f1) VIRTUAL)ENGINE=InnoDB;
+INSERT INTO t1(f1) VALUES(1);
 SET DEBUG_DBUG="+d,create_index_fail";
 SET DEBUG_SYNC="innodb_inplace_alter_table_enter SIGNAL con1_go WAIT_FOR alter_signal";
 ALTER TABLE t1 ADD INDEX(f2);

mysql-test/suite/gcol/t/virtual_index_drop.test

@@ -29,6 +29,7 @@ DROP TABLE t1;
 # new_vcol_info in index when rollback of alter happens
 
 CREATE TABLE t1(f1 INT, f2 INT AS (f1) VIRTUAL)ENGINE=InnoDB;
+INSERT INTO t1(f1) VALUES(1);
 SET DEBUG_DBUG="+d,create_index_fail";
 SET DEBUG_SYNC="innodb_inplace_alter_table_enter SIGNAL con1_go WAIT_FOR alter_signal";
 SEND ALTER TABLE t1 ADD COLUMN f3 INT AS (f1) VIRTUAL, ADD INDEX(f2, f3);
@@ -47,6 +48,7 @@ SHOW CREATE TABLE t1;
 DROP TABLE t1;
 
 CREATE TABLE t1(f1 INT, f2 INT AS (f1) VIRTUAL)ENGINE=InnoDB;
+INSERT INTO t1(f1) VALUES(1);
 SET DEBUG_DBUG="+d,create_index_fail";
 SET DEBUG_SYNC="innodb_inplace_alter_table_enter SIGNAL con1_go WAIT_FOR alter_signal";
 send ALTER TABLE t1 ADD INDEX(f2);

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

@@ -34,6 +34,7 @@ CREATE TABLE t1(f1 INT, f2 INT,
 PRIMARY KEY(f1, f2),
 UNIQUE INDEX uidx2 (f1, f2),
 UNIQUE INDEX uidx1 (f2))ENGINE=InnoDB;
+INSERT INTO t1 VALUES(2, 2);
 ALTER TABLE t1 DROP PRIMARY KEY;
 SHOW CREATE TABLE t1;
 Table	Create Table
@@ -66,6 +67,7 @@ test.t1	check	status	OK
 DROP TABLE t1;
 SET SQL_MODE= strict_trans_tables;
 CREATE TABLE t1(a INT UNIQUE) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1);
 SET DEBUG_SYNC='row_log_table_apply1_before SIGNAL dml WAIT_FOR dml_done';
 ALTER TABLE t1 MODIFY COLUMN a INT NOT NULL;
 connection con1;

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

@@ -80,6 +80,7 @@ SET DEBUG_SYNC='RESET';
 #
 CREATE TABLE t1 (f VARCHAR(8) CHARACTER SET latin1 COLLATE latin1_swedish_ci)
 ENGINE=InnoDB;
+INSERT INTO t1 VALUES('ZERO');
 connection con1;
 SET DEBUG_SYNC = 'row_log_table_apply1_before SIGNAL scanned WAIT_FOR insert_done';
 ALTER TABLE t1 MODIFY f VARCHAR(256) COLLATE latin1_german2_ci NOT NULL;
@@ -96,5 +97,6 @@ ALTER TABLE t1 CHANGE f eins VARCHAR(257) COLLATE latin1_german1_ci NOT NULL,
 ALGORITHM=INSTANT;
 SELECT * FROM t1;
 eins
+ZERO
 one
 DROP TABLE t1;

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

@@ -4,6 +4,7 @@
 #
 CREATE TABLE t0 (pk INT PRIMARY KEY) ENGINE=InnoDB;
 CREATE TABLE t1 (c CHAR(2) NOT NULL) ENGINE=InnoDB;
+INSERT INTO  t1 VALUES('cd');
 connect  con1,localhost,root,,;
 BEGIN;
 INSERT INTO t0 VALUES(1);
@@ -21,6 +22,7 @@ ERROR 23000: Duplicate entry 'a' for key 'PRIMARY'
 SET DEBUG_SYNC='RESET';
 SELECT * FROM t1;
 c
+cd
 ab
 ac
 DROP TABLE t0,t1;

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

@@ -1,5 +1,6 @@
 CREATE TABLE t0 (pk INT PRIMARY KEY) ENGINE=InnoDB;
 CREATE TABLE t1 (pk INT PRIMARY KEY, b INT) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(100, 100);
 connect  con1,localhost,root,,test;
 BEGIN;
 INSERT INTO t0 SET pk=1;

mysql-test/suite/innodb/r/innodb-alter-tempfile.result

@@ -61,7 +61,7 @@ connect  con1,localhost,root,,;
 BEGIN;
 DELETE FROM mysql.innodb_table_stats;
 connect  con2,localhost,root,,;
-SET DEBUG_SYNC='inplace_after_index_build SIGNAL blocked WAIT_FOR ever';
+SET DEBUG_SYNC='innodb_inplace_alter_table_enter SIGNAL blocked WAIT_FOR ever';
 ALTER TABLE t1 FORCE;
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR blocked';

mysql-test/suite/innodb/r/innodb-index-debug.result

@@ -81,6 +81,7 @@ COUNT(k1)	k2	k3
 drop table t1;
 create table t1(k1 int auto_increment primary key,
 k2 char(200),k3 char(200))engine=innodb;
+INSERT INTO t1 VALUES(1, "test", "test");
 SET DEBUG_SYNC= 'row_merge_after_scan
 SIGNAL opened WAIT_FOR flushed';
 ALTER TABLE t1 FORCE, ADD COLUMN k4 int;
@@ -100,6 +101,7 @@ SELECT COUNT(k1),k2,k3 FROM t1 GROUP BY k2,k3;
 COUNT(k1)	k2	k3
 480	aaa	bbb
 480	aaaa	bbbb
+1	test	test
 disconnect con1;
 connection default;
 show create table t1;
@@ -109,7 +111,7 @@ t1	CREATE TABLE `t1` (
   `k2` char(200) DEFAULT NULL,
   `k3` char(200) DEFAULT NULL,
   PRIMARY KEY (`k1`)
-) ENGINE=InnoDB AUTO_INCREMENT=1023 DEFAULT CHARSET=latin1
+) ENGINE=InnoDB AUTO_INCREMENT=1024 DEFAULT CHARSET=latin1
 drop table t1;
 drop table t480;
 #
@@ -117,6 +119,7 @@ drop table t480;
 # in online table rebuild
 #
 CREATE TABLE t1 (j INT UNIQUE, i INT UNIQUE) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(2, 2);
 connect  con1,localhost,root,,test;
 SET DEBUG_SYNC='row_log_table_apply1_before SIGNAL built WAIT_FOR log';
 ALTER TABLE t1 DROP j, FORCE;

mysql-test/suite/innodb/r/innodb-index-online.result

@@ -509,6 +509,7 @@ DROP TABLE t1;
 # MDEV-13205 assertion !dict_index_is_online_ddl(index) upon ALTER TABLE
 #
 CREATE TABLE t1 (c VARCHAR(64)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES('foo');
 SET DEBUG_SYNC = 'row_log_apply_before SIGNAL t1u_created WAIT_FOR dup_done';
 ALTER TABLE t1 ADD UNIQUE(c);
 connection con1;

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

@@ -171,6 +171,7 @@ connect stop_purge,localhost,root;
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
 connect ddl,localhost,root,,test;
 DELETE FROM t1;
+INSERT INTO t1 VALUES(1, 2);
 SET DEBUG_SYNC='row_log_table_apply1_before SIGNAL copied WAIT_FOR logged';
 ALTER TABLE t1 FORCE;
 connection default;
@@ -449,6 +450,7 @@ DROP TABLE t1;
 CREATE TABLE t1
 (a INT NOT NULL, b INT, c INT, d INT, e INT, f INT, g INT, h INT, i TEXT)
 ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1, 2, 3, 4, 5, 6, 7, 8, "test");
 ALTER TABLE t1 MODIFY a INT NULL;
 SET DEBUG_SYNC='innodb_inplace_alter_table_enter SIGNAL alter WAIT_FOR go';
 ALTER TABLE t1 ADD PRIMARY KEY (a);
@@ -462,6 +464,7 @@ connection default;
 disconnect con1;
 SELECT * FROM t1;
 a	b	c	d	e	f	g	h	i
+1	2	3	4	5	6	7	8	test
 DROP TABLE t1;
 SET DEBUG_SYNC=RESET;
 # End of 10.4 tests

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

@@ -24,6 +24,7 @@ CREATE TABLE t1(f1 INT, f2 INT,
 		PRIMARY KEY(f1, f2),
 		UNIQUE INDEX uidx2 (f1, f2),
 		UNIQUE INDEX uidx1 (f2))ENGINE=InnoDB;
+INSERT INTO t1 VALUES(2, 2);
 ALTER TABLE t1 DROP PRIMARY KEY;
 SHOW CREATE TABLE t1;
 SET DEBUG_SYNC = 'innodb_inplace_alter_table_enter
@@ -42,6 +43,7 @@ DROP TABLE t1;
 
 SET SQL_MODE= strict_trans_tables;
 CREATE TABLE t1(a INT UNIQUE) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1);
 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;

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

@@ -75,7 +75,7 @@ SET DEBUG_SYNC='RESET';
 --echo #
 CREATE TABLE t1 (f VARCHAR(8) CHARACTER SET latin1 COLLATE latin1_swedish_ci)
 ENGINE=InnoDB;
-
+INSERT INTO t1 VALUES('ZERO');
 connection con1;
 SET DEBUG_SYNC = 'row_log_table_apply1_before SIGNAL scanned WAIT_FOR insert_done';
 send ALTER TABLE t1 MODIFY f VARCHAR(256) COLLATE latin1_german2_ci NOT NULL;

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

@@ -9,6 +9,7 @@
 
 CREATE TABLE t0 (pk INT PRIMARY KEY) ENGINE=InnoDB;
 CREATE TABLE t1 (c CHAR(2) NOT NULL) ENGINE=InnoDB;
+INSERT INTO  t1 VALUES('cd');
 
 connect (con1,localhost,root,,);
 BEGIN;

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

@@ -4,6 +4,7 @@
 
 CREATE TABLE t0 (pk INT PRIMARY KEY) ENGINE=InnoDB;
 CREATE TABLE t1 (pk INT PRIMARY KEY, b INT) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(100, 100);
 
 --connect (con1,localhost,root,,test)
 BEGIN;

mysql-test/suite/innodb/t/innodb-alter-tempfile.test

@@ -80,7 +80,7 @@ BEGIN;
 DELETE FROM mysql.innodb_table_stats;
 
 connect (con2,localhost,root,,);
-SET DEBUG_SYNC='inplace_after_index_build SIGNAL blocked WAIT_FOR ever';
+SET DEBUG_SYNC='innodb_inplace_alter_table_enter SIGNAL blocked WAIT_FOR ever';
 send ALTER TABLE t1 FORCE;
 
 connection default;

mysql-test/suite/innodb/t/innodb-index-debug.test

@@ -96,6 +96,7 @@ drop table t1;
 # Log file creation failure.
 create table t1(k1 int auto_increment primary key,
 k2 char(200),k3 char(200))engine=innodb;
+INSERT INTO t1 VALUES(1, "test", "test");
 SET DEBUG_SYNC= 'row_merge_after_scan
 SIGNAL opened WAIT_FOR flushed';
 send ALTER TABLE t1 FORCE, ADD COLUMN k4 int;
@@ -122,6 +123,7 @@ drop table t480;
 --echo #
 
 CREATE TABLE t1 (j INT UNIQUE, i INT UNIQUE) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(2, 2);
 --connect (con1,localhost,root,,test)
 SET DEBUG_SYNC='row_log_table_apply1_before SIGNAL built WAIT_FOR log';
 --send

mysql-test/suite/innodb/t/innodb-index-online.test

@@ -477,6 +477,7 @@ DROP TABLE t1;
 --echo # MDEV-13205 assertion !dict_index_is_online_ddl(index) upon ALTER TABLE
 --echo #
 CREATE TABLE t1 (c VARCHAR(64)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES('foo');
 SET DEBUG_SYNC = 'row_log_apply_before SIGNAL t1u_created WAIT_FOR dup_done';
 send ALTER TABLE t1 ADD UNIQUE(c);
 

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

@@ -186,6 +186,7 @@ connect stop_purge,localhost,root;
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
 connect ddl,localhost,root,,test;
 DELETE FROM t1;
+INSERT INTO t1 VALUES(1, 2);
 SET DEBUG_SYNC='row_log_table_apply1_before SIGNAL copied WAIT_FOR logged';
 send ALTER TABLE t1 FORCE;
 connection default;
@@ -519,7 +520,7 @@ DROP TABLE t1;
 CREATE TABLE t1
 (a INT NOT NULL, b INT, c INT, d INT, e INT, f INT, g INT, h INT, i TEXT)
 ENGINE=InnoDB;
-
+INSERT INTO t1 VALUES(1, 2, 3, 4, 5, 6, 7, 8, "test");
 ALTER TABLE t1 MODIFY a INT NULL;
 
 SET DEBUG_SYNC='innodb_inplace_alter_table_enter SIGNAL alter WAIT_FOR go';

mysql-test/suite/innodb_fts/r/misc_debug.result

@@ -30,6 +30,7 @@ DROP TABLE t2, t1;
 # MDEV-25200 Index count mismatch due to aborted FULLTEXT INDEX
 #
 CREATE TABLE t1(a INT, b TEXT, c TEXT, FULLTEXT INDEX(b)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1, "test", "test_1");
 connect con1,localhost,root,,test;
 SET DEBUG_DBUG="+d,innodb_OOM_inplace_alter";
 SET DEBUG_SYNC='innodb_commit_inplace_alter_table_enter SIGNAL s2 WAIT_FOR g2';
@@ -39,6 +40,7 @@ SET DEBUG_SYNC='now WAIT_FOR s2';
 START TRANSACTION;
 SELECT * FROM t1;
 a	b	c
+1	test	test_1
 SET DEBUG_SYNC='now SIGNAL g2';
 connection con1;
 ERROR HY000: Out of memory.

mysql-test/suite/innodb_fts/t/misc_debug.test

@@ -59,6 +59,7 @@ DROP TABLE t2, t1;
 --echo # MDEV-25200 Index count mismatch due to aborted FULLTEXT INDEX
 --echo #
 CREATE TABLE t1(a INT, b TEXT, c TEXT, FULLTEXT INDEX(b)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1, "test", "test_1");
 connect(con1,localhost,root,,test);
 SET DEBUG_DBUG="+d,innodb_OOM_inplace_alter";
 SET DEBUG_SYNC='innodb_commit_inplace_alter_table_enter SIGNAL s2 WAIT_FOR g2';

sql/handler.h

@@ -2579,6 +2579,9 @@ public:
   /** true when InnoDB should abort the alter when table is not empty */
   bool error_if_not_empty;
 
+  /** True when DDL should avoid downgrading the MDL */
+  bool mdl_exclusive_after_prepare= false;
+
   Alter_inplace_info(HA_CREATE_INFO *create_info_arg,
                      Alter_info *alter_info_arg,
                      KEY *key_info_arg, uint key_count_arg,

sql/my_json_writer.cc

@@ -18,6 +18,14 @@
 #include "sql_string.h"
 #include "my_json_writer.h"
 
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+bool Json_writer::named_item_expected() const
+{
+  return named_items_expectation.size()
+      && named_items_expectation.back();
+}
+#endif
+
 void Json_writer::append_indent()
 {
   if (!document_start)
@@ -26,9 +34,21 @@ void Json_writer::append_indent()
     output.append(' ');
 }
 
+inline void Json_writer::on_start_object()
+{
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+  if(!fmt_helper.is_making_writer_calls())
+  {
+    VALIDITY_ASSERT(got_name == named_item_expected());
+    named_items_expectation.push_back(true);
+  }
+#endif
+  fmt_helper.on_start_object();
+}
+
 void Json_writer::start_object()
 {
-  fmt_helper.on_start_object();
+  on_start_object();
 
   if (!element_started)
     start_element();
@@ -38,10 +58,22 @@ void Json_writer::start_object()
   first_child=true;
   element_started= false;
   document_start= false;
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+  got_name= false;
+#endif
 }
 
 void Json_writer::start_array()
 {
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+  if(!fmt_helper.is_making_writer_calls())
+  {
+    VALIDITY_ASSERT(got_name == named_item_expected());
+    named_items_expectation.push_back(false);
+    got_name= false;
+  }
+#endif
+
   if (fmt_helper.on_start_array())
     return;
 
@@ -58,6 +90,12 @@ void Json_writer::start_array()
 
 void Json_writer::end_object()
 {
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+  VALIDITY_ASSERT(named_item_expected());
+  named_items_expectation.pop_back();
+  VALIDITY_ASSERT(!got_name);
+  got_name= false;
+#endif
   indent_level-=INDENT_SIZE;
   if (!first_child)
     append_indent();
@@ -68,6 +106,11 @@ void Json_writer::end_object()
 
 void Json_writer::end_array()
 {
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+  VALIDITY_ASSERT(!named_item_expected());
+  named_items_expectation.pop_back();
+  got_name= false;
+#endif
   if (fmt_helper.on_end_array())
     return;
   indent_level-=INDENT_SIZE;
@@ -80,9 +123,13 @@ void Json_writer::end_array()
 Json_writer& Json_writer::add_member(const char *name)
 {
   size_t len= strlen(name);
-  if (fmt_helper.on_add_member(name, len))
+  return add_member(name, len);
-    return *this; // handled
+}
 
+Json_writer& Json_writer::add_member(const char *name, size_t len)
+{
+  if (!fmt_helper.on_add_member(name, len))
+  {
     // assert that we are in an object
     DBUG_ASSERT(!element_started);
     start_element();
@@ -90,21 +137,11 @@ Json_writer& Json_writer::add_member(const char *name)
     output.append('"');
     output.append(name, len);
     output.append("\": ", 3);
-  return *this;
   }
-
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
-Json_writer& Json_writer::add_member(const char *name, size_t len)
+  if (!fmt_helper.is_making_writer_calls())
-{
+    got_name= true;
-  if (fmt_helper.on_add_member(name, len))
+#endif
-    return *this; // handled
-
-  // assert that we are in an object
-  DBUG_ASSERT(!element_started);
-  start_element();
-
-  output.append('"');
-  output.append(name, len);
-  output.append("\": ");
   return *this;
 }
 
@@ -200,7 +237,14 @@ void Json_writer::add_null()
 void Json_writer::add_unquoted_str(const char* str)
 {
   size_t len= strlen(str);
-  if (fmt_helper.on_add_str(str, len))
+  add_unquoted_str(str, len);
+}
+
+void Json_writer::add_unquoted_str(const char* str, size_t len)
+{
+  VALIDITY_ASSERT(fmt_helper.is_making_writer_calls() ||
+                  got_name == named_item_expected());
+  if (on_add_str(str, len))
     return;
 
   if (!element_started)
@@ -210,31 +254,19 @@ void Json_writer::add_unquoted_str(const char* str)
   element_started= false;
 }
 
-void Json_writer::add_unquoted_str(const char* str, size_t len)
+inline bool Json_writer::on_add_str(const char *str, size_t num_bytes)
 {
-  if (fmt_helper.on_add_str(str, len))
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
-    return;
+  got_name= false;
-
+#endif
-  if (!element_started)
+  bool helped= fmt_helper.on_add_str(str, num_bytes);
-    start_element();
+  return helped;
-
-  output.append(str, len);
-  element_started= false;
 }
 
 void Json_writer::add_str(const char *str)
 {
   size_t len= strlen(str);
-  if (fmt_helper.on_add_str(str, len))
+  add_str(str, len);
-    return;
-
-  if (!element_started)
-    start_element();
-
-  output.append('"');
-  output.append(str, len);
-  output.append('"');
-  element_started= false;
 }
 
 /*
@@ -243,7 +275,9 @@ void Json_writer::add_str(const char *str)
 
 void Json_writer::add_str(const char* str, size_t num_bytes)
 {
-  if (fmt_helper.on_add_str(str, num_bytes))
+  VALIDITY_ASSERT(fmt_helper.is_making_writer_calls() ||
+                  got_name == named_item_expected());
+  if (on_add_str(str, num_bytes))
     return;
 
   if (!element_started)

sql/my_json_writer.h

@@ -17,9 +17,19 @@
 #define JSON_WRITER_INCLUDED
 
 #include "my_base.h"
-#include "sql_select.h"
 
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST) || defined ENABLED_JSON_WRITER_CONSISTENCY_CHECKS
 #include <vector>
+#endif
+
+#ifdef JSON_WRITER_UNIT_TEST
+#include "sql_string.h"
+// Also, mock objects are defined in my_json_writer-t.cc
+#define VALIDITY_ASSERT(x) if (!(x)) this->invalid_json= true;
+#else
+#include "sql_select.h"
+#define VALIDITY_ASSERT(x) DBUG_ASSERT(x)
+#endif
 
 class Opt_trace_stmt;
 class Opt_trace_context;
@@ -99,6 +109,15 @@ public:
 
   bool on_add_str(const char *str, size_t num_bytes);
 
+  /*
+    Returns true if the helper is flushing its buffer and is probably
+    making calls back to its Json_writer. (The Json_writer uses this
+    function to avoid re-doing the processing that it has already done
+    before making a call to fmt_helper)
+  */
+  bool is_making_writer_calls() const { return state == DISABLED; }
+
+private:
   void flush_on_one_line();
   void disable_and_flush();
 };
@@ -185,6 +204,25 @@ private:
 
 class Json_writer
 {
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+  /*
+    In debug mode, Json_writer will fail and assertion if one attempts to
+    produce an invalid JSON document (e.g. JSON array having named elements).
+  */
+  std::vector<bool> named_items_expectation;
+
+  bool named_item_expected() const;
+
+  bool got_name;
+
+#ifdef JSON_WRITER_UNIT_TEST
+public:
+  // When compiled for unit test, creating invalid JSON will set this to true
+  // instead of an assertion.
+  bool invalid_json= false;
+#endif
+#endif
+
 public:
   /* Add a member. We must be in an object. */
   Json_writer& add_member(const char *name);
@@ -208,6 +246,10 @@ public:
 private:
   void add_unquoted_str(const char* val);
   void add_unquoted_str(const char* val, size_t len);
+
+  bool on_add_str(const char *str, size_t num_bytes);
+  void on_start_object();
+
 public:
   /* Start a child object */
   void start_object();
@@ -225,6 +267,9 @@ public:
   size_t get_truncated_bytes() { return output.get_truncated_bytes(); }
 
   Json_writer() : 
+#if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
+    got_name(false),
+#endif
     indent_level(0), document_start(true), element_started(false), 
     first_child(true)
   {
@@ -312,6 +357,9 @@ public:
 /* A common base for Json_writer_object and Json_writer_array */
 class Json_writer_struct
 {
+  Json_writer_struct(const Json_writer_struct&)= delete;
+  Json_writer_struct& operator=(const Json_writer_struct&)= delete;
+
 #ifdef ENABLED_JSON_WRITER_CONSISTENCY_CHECKS
   static thread_local std::vector<bool> named_items_expectation;
 #endif
@@ -372,24 +420,18 @@ private:
     my_writer->add_member(name);
   }
 public:
-  explicit Json_writer_object(THD *thd)
+  explicit Json_writer_object(THD* thd, const char *str= nullptr)
-  : Json_writer_struct(thd, true)
-  {
-#ifdef ENABLED_JSON_WRITER_CONSISTENCY_CHECKS
-    DBUG_ASSERT(!named_item_expected());
-#endif
-    if (unlikely(my_writer))
-      my_writer->start_object();
-  }
-
-  explicit Json_writer_object(THD* thd, const char *str)
   : Json_writer_struct(thd, true)
   {
 #ifdef ENABLED_JSON_WRITER_CONSISTENCY_CHECKS
     DBUG_ASSERT(named_item_expected());
 #endif
     if (unlikely(my_writer))
-      my_writer->add_member(str).start_object();
+    {
+      if (str)
+        my_writer->add_member(str);
+      my_writer->start_object();
+    }
   }
 
   ~Json_writer_object()

sql/opt_range.cc

@@ -370,7 +370,7 @@ TRP_ROR_INTERSECT *get_best_covering_ror_intersect(PARAM *param,
                                                    double read_time);
 static
 TABLE_READ_PLAN *get_best_disjunct_quick(PARAM *param, SEL_IMERGE *imerge,
-                                         double read_time);
+                                         double read_time, bool named_trace= false);
 static
 TABLE_READ_PLAN *merge_same_index_scans(PARAM *param, SEL_IMERGE *imerge,
                                         TRP_INDEX_MERGE *imerge_trp,
@@ -5085,7 +5085,7 @@ double get_sweep_read_cost(const PARAM *param, ha_rows records)
 
 static
 TABLE_READ_PLAN *get_best_disjunct_quick(PARAM *param, SEL_IMERGE *imerge,
-                                         double read_time)
+                                         double read_time, bool named_trace)
 {
   SEL_TREE **ptree;
   TRP_INDEX_MERGE *imerge_trp= NULL;
@@ -5133,7 +5133,8 @@ TABLE_READ_PLAN *get_best_disjunct_quick(PARAM *param, SEL_IMERGE *imerge,
                                              n_child_scans)))
     DBUG_RETURN(NULL);
 
-  Json_writer_object trace_best_disjunct(thd);
+  const char* trace_best_disjunct_obj_name= named_trace ? "best_disjunct_quick" : nullptr;
+  Json_writer_object trace_best_disjunct(thd, trace_best_disjunct_obj_name);
   Json_writer_array to_merge(thd, "indexes_to_merge");
   /*
     Collect best 'range' scan for each of disjuncts, and, while doing so,
@@ -5489,7 +5490,7 @@ TABLE_READ_PLAN *merge_same_index_scans(PARAM *param, SEL_IMERGE *imerge,
   DBUG_ASSERT(imerge->trees_next>imerge->trees);
 
   if (imerge->trees_next-imerge->trees > 1)
-    trp= get_best_disjunct_quick(param, imerge, read_time);
+    trp= get_best_disjunct_quick(param, imerge, read_time, true);
   else
   {
     /*
@@ -5677,7 +5678,7 @@ void print_keyparts(THD *thd, KEY *key, uint key_parts)
   DBUG_ASSERT(thd->trace_started());
 
   KEY_PART_INFO *part= key->key_part;
-  Json_writer_array keyparts= Json_writer_array(thd, "keyparts");
+  Json_writer_array keyparts(thd, "keyparts");
   for(uint i= 0; i < key_parts; i++, part++)
     keyparts.add(part->field->field_name);
 }

sql/opt_subselect.cc

@@ -3827,9 +3827,9 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
       Json_writer_array semijoin_plan(thd, "join_order");
       for (i= first + sjm->tables; i <= tablenr; i++)
       {
+        Json_writer_object trace_one_table(thd);
         if (unlikely(thd->trace_started()))
         {
-          Json_writer_object trace_one_table(thd);
           trace_one_table.add_table_name(join->best_positions[i].table);
         }
         best_access_path(join, join->best_positions[i].table, rem_tables,
@@ -3866,9 +3866,9 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
       Json_writer_array semijoin_plan(thd, "join_order");
       for (idx= first; idx <= tablenr; idx++)
       {
+        Json_writer_object trace_one_table(thd);
         if (unlikely(thd->trace_started()))
         {
-          Json_writer_object trace_one_table(thd);
           trace_one_table.add_table_name(join->best_positions[idx].table);
         }
         if (join->best_positions[idx].use_join_buffer)
@@ -3905,9 +3905,9 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
       Json_writer_array semijoin_plan(thd, "join_order");
       for (idx= first; idx <= tablenr; idx++)
       {
+        Json_writer_object trace_one_table(thd);
         if (unlikely(thd->trace_started()))
         {
-          Json_writer_object trace_one_table(thd);
           trace_one_table.add_table_name(join->best_positions[idx].table);
         }
         if (join->best_positions[idx].use_join_buffer || (idx == first))

sql/sql_table.cc

@@ -8001,7 +8001,8 @@ static bool mysql_inplace_alter_table(THD *thd,
     lock for prepare phase under LOCK TABLES in the same way as when
     exclusive lock is required for duration of the whole statement.
   */
-  if (inplace_supported == HA_ALTER_INPLACE_EXCLUSIVE_LOCK ||
+  if (!ha_alter_info->mdl_exclusive_after_prepare &&
+      (inplace_supported == HA_ALTER_INPLACE_EXCLUSIVE_LOCK ||
        ((inplace_supported == HA_ALTER_INPLACE_COPY_NO_LOCK ||
         inplace_supported == HA_ALTER_INPLACE_COPY_LOCK ||
         inplace_supported == HA_ALTER_INPLACE_NOCOPY_NO_LOCK ||
@@ -8009,7 +8010,7 @@ static bool mysql_inplace_alter_table(THD *thd,
         inplace_supported == HA_ALTER_INPLACE_INSTANT) &&
        (thd->locked_tables_mode == LTM_LOCK_TABLES ||
         thd->locked_tables_mode == LTM_PRELOCKED_UNDER_LOCK_TABLES)) ||
-      alter_info->requested_lock == Alter_info::ALTER_TABLE_LOCK_EXCLUSIVE)
+      alter_info->requested_lock == Alter_info::ALTER_TABLE_LOCK_EXCLUSIVE))
   {
     if (wait_while_table_is_used(thd, table, HA_EXTRA_FORCE_REOPEN))
       goto cleanup;

storage/innobase/handler/handler0alter.cc

@@ -1913,9 +1913,14 @@ innobase_fts_check_doc_id_col(
 
 /** Check whether the table is empty.
 @param[in]	table			table to be checked
+@param[in]	ignore_delete_marked	Ignore the delete marked
+					flag record
 @return true if table is empty */
-static bool innobase_table_is_empty(const dict_table_t *table)
+static bool innobase_table_is_empty(const dict_table_t *table,
+				    bool ignore_delete_marked=true)
 {
+  if (!table->space)
+    return false;
   dict_index_t *clust_index= dict_table_get_first_index(table);
   mtr_t mtr;
   btr_pcur_t pcur;
@@ -1953,12 +1958,16 @@ next_page:
   }
 
   rec= page_cur_get_rec(cur);
-  if (rec_get_deleted_flag(rec, dict_table_is_comp(table)));
+  if (rec_get_deleted_flag(rec, dict_table_is_comp(table)))
-  else if (!page_rec_is_supremum(rec))
   {
+    if (ignore_delete_marked)
+      goto scan_leaf;
+non_empty:
     mtr.commit();
     return false;
   }
+  else if (!page_rec_is_supremum(rec))
+    goto non_empty;
   else
   {
     next_page= true;
@@ -6764,6 +6773,7 @@ wrong_column_name:
 		DBUG_ASSERT(num_fts_index <= 1);
 		DBUG_ASSERT(!ctx->online || num_fts_index == 0);
 		DBUG_ASSERT(!ctx->online
+			    || !ha_alter_info->mdl_exclusive_after_prepare
 			    || ctx->add_autoinc == ULINT_UNDEFINED);
 		DBUG_ASSERT(!ctx->online
 			    || !innobase_need_rebuild(ha_alter_info, old_table)
@@ -7582,6 +7592,20 @@ ha_innobase::prepare_inplace_alter_table(
 		DBUG_RETURN(false);
 	}
 
+#ifdef WITH_PARTITION_STORAGE_ENGINE
+	if (table->part_info == NULL) {
+#endif
+	/* Ignore the MDL downgrade when table is empty.
+	This optimization is disabled for partition table. */
+	ha_alter_info->mdl_exclusive_after_prepare =
+		innobase_table_is_empty(m_prebuilt->table, false);
+	if (ha_alter_info->online
+	    && ha_alter_info->mdl_exclusive_after_prepare) {
+		ha_alter_info->online = false;
+	}
+#ifdef WITH_PARTITION_STORAGE_ENGINE
+	}
+#endif
 	indexed_table = m_prebuilt->table;
 
 	/* ALTER TABLE will not implicitly move a table from a single-table
@@ -8366,7 +8390,9 @@ ha_innobase::inplace_alter_table(
 
 	DEBUG_SYNC(m_user_thd, "innodb_inplace_alter_table_enter");
 
-	if (!(ha_alter_info->handler_flags & INNOBASE_ALTER_DATA)) {
+	/* Ignore the inplace alter phase when table is empty */
+	if (!(ha_alter_info->handler_flags & INNOBASE_ALTER_DATA)
+	    || ha_alter_info->mdl_exclusive_after_prepare) {
 ok_exit:
 		DEBUG_SYNC(m_user_thd, "innodb_after_inplace_alter_table");
 		DBUG_RETURN(false);

unittest/sql/CMakeLists.txt

@@ -36,3 +36,8 @@ ADD_EXECUTABLE(mf_iocache-t mf_iocache-t.cc ../../sql/mf_iocache_encr.cc)
 TARGET_LINK_LIBRARIES(mf_iocache-t mysys mytap mysys_ssl)
 ADD_DEPENDENCIES(mf_iocache-t GenError)
 MY_ADD_TEST(mf_iocache)
+
+# Json writer needs String which needs sql library
+ADD_EXECUTABLE(my_json_writer-t my_json_writer-t.cc dummy_builtins.cc)
+TARGET_LINK_LIBRARIES(my_json_writer-t sql mytap)
+MY_ADD_TEST(my_json_writer)

unittest/sql/my_json_writer-t.cc

@@ -0,0 +1,128 @@
+/*
+   Copyright (c) 2021, MariaDB Corporation.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
+
+#include <my_global.h>
+#include <my_pthread.h>
+#include <my_sys.h>
+#include <stdio.h>
+#include <tap.h>
+
+/*
+  Unit tests for class Json_writer. At the moment there are only tests for the
+  "Fail an assertion if one attempts to produce invalid JSON" feature.
+*/
+
+struct TABLE;
+struct JOIN_TAB;
+class Json_writer;
+
+
+/* Several fake objects */
+class Opt_trace 
+{
+public:
+  void enable_tracing_if_required() {}
+  void disable_tracing_if_required() {}
+  Json_writer *get_current_json() { return nullptr; }
+};
+
+class THD 
+{
+public:
+  Opt_trace opt_trace;
+};
+
+#define JSON_WRITER_UNIT_TEST
+#include "../sql/my_json_writer.h"
+#include "../sql/my_json_writer.cc"
+
+int main(int args, char **argv)
+{
+  plan(NO_PLAN);
+  diag("Testing Json_writer checks");
+
+  {
+    Json_writer w;
+    w.start_object();
+    w.add_member("foo"); 
+    w.end_object();
+    ok(w.invalid_json, "Started a name but didn't add a value");
+  }
+
+  {
+    Json_writer w;
+    w.start_object();
+    w.add_ull(123);
+    ok(w.invalid_json, "Unnamed value in an object");
+  }
+
+  {
+    Json_writer w;
+    w.start_array();
+    w.add_member("bebebe").add_ull(345);
+    ok(w.invalid_json, "Named member in array");
+  }
+
+  {
+    Json_writer w;
+    w.start_object();
+    w.start_array();
+    ok(w.invalid_json, "Unnamed array in an object");
+  }
+
+  {
+    Json_writer w;
+    w.start_object();
+    w.start_object();
+    ok(w.invalid_json, "Unnamed object in an object");
+  }
+
+  {
+    Json_writer w;
+    w.start_array();
+    w.add_member("zzz");
+    w.start_object();
+    ok(w.invalid_json, "Named object in an array");
+  }
+  {
+    Json_writer w;
+    w.start_array();
+    w.add_member("zzz");
+    w.start_array();
+    ok(w.invalid_json, "Named array in an array");
+  }
+
+  {
+    Json_writer w;
+    w.start_array();
+    w.end_object();
+    ok(w.invalid_json, "JSON object end of array");
+  }
+
+  {
+    Json_writer w;
+    w.start_object();
+    w.end_array();
+    ok(w.invalid_json, "JSON array end of object");
+  }
+
+
+
+  diag("Done");
+
+  return exit_status();
+}
+