MDEV-18323 Convert MySQL JSON type to MariaDB TEXT in mysql_upgrade

This patch solves two key problems.
1. There is a type number clash between MySQL and MariaDB. The number
   245, used for MariaDB Virtual Fields is the same as MySQL's JSON.
   This leads to corrupt FRM errors if unhandled. The code properly
   checks frm table version number and if it matches 5.7+ (until 10.0+)
   it will assume it is dealing with a MySQL table with the JSON
   datatype.
2. MySQL JSON datatype uses a proprietary format to pack JSON data. The
   patch introduces a datatype plugin which parses the format and convers
   it to its string representation.

The intended conversion path is to only use the JSON datatype within
ALTER TABLE <table> FORCE, to force a table recreate. This happens
during mysql_upgrade or via a direct ALTER TABLE <table> FORCE.

mysql-test/main/mysql_json_table_recreate.opt

+--plugin-load=$TYPE_MYSQL_JSON_SO

mysql-test/main/mysql_json_table_recreate.result

+#
+# The following test takes 2 tables containing a JSON column and attempts
+# to repair them.
+#
+# The tables header is (Description, Expected, Actual), where description
+# shows a brief description what the JSON value is testing in the MariaDB
+# implementation. Expected is the longtext string and actual is the JSON
+# column that needs to be converted to MariaDB's representation of
+# LONGTEXT.
+#
+call mtr.add_suppression("Table rebuild required");
+call mtr.add_suppression("is marked as crashed");
+call mtr.add_suppression("Checking");
+SET NAMES utf8;
+#
+# Check that only ALTER TABLE ... FORCE is allowed on a MySQL 5.7 table
+# with a JSON column.
+#
+show create table tempty;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.tempty` FORCE" or dump/reload to fix it!
+select * from tempty;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.tempty` FORCE" or dump/reload to fix it!
+alter table tempty force;
+show create table tempty;
+Table	Create Table
+tempty	CREATE TABLE `tempty` (
+  `t` longtext CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+show create table mysql_json_test;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.mysql_json_test` FORCE" or dump/reload to fix it!
+select * from mysql_json_test;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.mysql_json_test` FORCE" or dump/reload to fix it!
+LOCK TABLES mysql_json_test WRITE;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.mysql_json_test` FORCE" or dump/reload to fix it!
+alter table mysql_json_test force;
+select description, expected, actual, expected = actual from mysql_json_test;
+description	expected	actual	expected = actual
+Array LITERALS: 	["prefix", false, "suffix", 1]	["prefix", false, "suffix", 1]	1
+Array LITERALS: 	["prefix", null, "suffix", 1]	["prefix", null, "suffix", 1]	1
+Array LITERALS: 	["prefix", true, "suffix", 1]	["prefix", true, "suffix", 1]	1
+DateTime as Raw Value: 	"2015-01-15 23:24:25.000000"	"2015-01-15 23:24:25.000000"	1
+DateTime as Raw Value: 	"2015-01-15 23:24:25.000000"	"2015-01-15 23:24:25.000000"	1
+DateTime as Raw Value: 	"2015-01-15"	"2015-01-15"	1
+DateTime as Raw Value: 	"23:24:25.000000"	"23:24:25.000000"	1
+Empty JSON Object/Array: 	[]	[]	1
+Empty JSON Object/Array: 	{}	{}	1
+GeoJSON	{"type": "GeometryCollection", "geometries": []}	{"type": "GeometryCollection", "geometries": []}	1
+GeoJSON	{"type": "LineString", "coordinates": [[0, 5], [5, 10], [10, 15]]}	{"type": "LineString", "coordinates": [[0, 5], [5, 10], [10, 15]]}	1
+GeoJSON	{"type": "MultiPoint", "coordinates": [[1, 1], [2, 2], [3, 3]]}	{"type": "MultiPoint", "coordinates": [[1, 1], [2, 2], [3, 3]]}	1
+GeoJSON	{"type": "Point", "coordinates": [11.1111, 12.22222]}	{"type": "Point", "coordinates": [11.1111, 12.22222]}	1
+JSON LITERALS: 	{"val": false}	{"val": false}	1
+JSON LITERALS: 	{"val": null}	{"val": null}	1
+JSON LITERALS: 	{"val": true}	{"val": true}	1
+Opaque Types: opaque_mysql_type_binary	"base64:type254:YWJjAAAAAAAAAA=="	"base64:type254:YWJjAAAAAAAAAA=="	1
+Opaque Types: opaque_mysql_type_bit	"base64:type16:yv4="	"base64:type16:yv4="	1
+Opaque Types: opaque_mysql_type_blob	"base64:type252:yv66vg=="	"base64:type252:yv66vg=="	1
+Opaque Types: opaque_mysql_type_date	"2015-01-15"	"2015-01-15"	1
+Opaque Types: opaque_mysql_type_datetime	"2015-01-15 23:24:25.000000"	"2015-01-15 23:24:25.000000"	1
+Opaque Types: opaque_mysql_type_enum	"b"	"b"	1
+Opaque Types: opaque_mysql_type_geom	{"type": "Point", "coordinates": [1, 1]}	{"type": "Point", "coordinates": [1, 1]}	1
+Opaque Types: opaque_mysql_type_longblob	"base64:type251:yv66vg=="	"base64:type251:yv66vg=="	1
+Opaque Types: opaque_mysql_type_mediumblob	"base64:type250:yv66vg=="	"base64:type250:yv66vg=="	1
+Opaque Types: opaque_mysql_type_set	"b,c"	"b,c"	1
+Opaque Types: opaque_mysql_type_time	"23:24:25.000000"	"23:24:25.000000"	1
+Opaque Types: opaque_mysql_type_tinyblob	"base64:type249:yv66vg=="	"base64:type249:yv66vg=="	1
+Opaque Types: opaque_mysql_type_varbinary	"base64:type15:YWJj"	"base64:type15:YWJj"	1
+Opaque Types: opaque_mysql_type_varchar	"base64:type15:Zm9v"	"base64:type15:Zm9v"	1
+Opaque Types: opaque_mysql_type_year	"base64:type13:MjAxOQ=="	"base64:type13:MjAxOQ=="	1
+Raw LITERALS: 	false	false	1
+Raw LITERALS: 	null	null	1
+Raw LITERALS: 	true	true	1
+Raw doubles as JSON	-2.2250738585072014e-308	-2.2250738585072014e-308	1
+Raw doubles as JSON	-5678.987	-5678.987	1
+Raw doubles as JSON	0.0	0.0	1
+Raw doubles as JSON	2.2250738585072014e-308	2.2250738585072014e-308	1
+Raw doubles as JSON	3.14	3.14	1
+Raw integers as JSON	-127	-127	1
+Raw integers as JSON	-2147483648	-2147483648	1
+Raw integers as JSON	-32768	-32768	1
+Raw integers as JSON	-9223372036854775807	-9223372036854775807	1
+Raw integers as JSON	0	0	1
+Raw integers as JSON	128	128	1
+Raw integers as JSON	18446744073709551615	18446744073709551615	1
+Raw integers as JSON	2147483647	2147483647	1
+Raw integers as JSON	32767	32767	1
+Raw integers as JSON	4294967295	4294967295	1
+Raw integers as JSON	65535	65535	1
+Raw integers as JSON	65536	65536	1
+Raw integers as JSON	9223372036854775807	9223372036854775807	1
+Simple Array as Base Key	[1, 2, 3, 4, 5, [], "a", "b", "c"]	[1, 2, 3, 4, 5, [], "a", "b", "c"]	1
+Simple Array as Value	{"a": [1, 2], "b": ["x", "y"]}	{"a": [1, 2], "b": ["x", "y"]}	1
+Simple JSON test	{"key1": "val1", "key2": "val2"}	{"key1": "val1", "key2": "val2"}	1
+Special Characters: 	""	""	1
+Special Characters: 	"'"	"'"	1
+Special Characters: 	"'"	"'"	1
+Special Characters: 	"'"	"'"	1
+Special Characters: 	"''"	"''"	1
+Special Characters: 	"\""	"\""	1
+Special Characters: 	"\\"	"\\"	1
+Special Characters: 	"\\b"	"\\b"	1
+Special Characters: 	"\b"	"\b"	1
+Special Characters: 	"\f"	"\f"	1
+Special Characters: 	"\n"	"\n"	1
+Special Characters: 	"\r"	"\r"	1
+Special Characters: 	"\t"	"\t"	1
+Special Characters: 	"f"	"f"	1
+Special Characters: 	"key1 - with \" val "	"key1 - with \" val "	1
+Special Characters: 	"q"	"q"	1
+Special Characters: 	"some_string"	"some_string"	1
+Special Characters: 	["a ' b", "c ' d"]	["a ' b", "c ' d"]	1
+Special Characters: 	["a \" b", "c \" d"]	["a \" b", "c \" d"]	1
+Special Characters: 	["a \\ b", "c \\ d"]	["a \\ b", "c \\ d"]	1
+Special Characters: 	["a \b b", "c \b d"]	["a \b b", "c \b d"]	1
+Special Characters: 	["a \f b", "c \f d"]	["a \f b", "c \f d"]	1
+Special Characters: 	["a \r b", "c \r d"]	["a \r b", "c \r d"]	1
+Special Characters: 	["a \t b", "c \t d"]	["a \t b", "c \t d"]	1
+Special Characters: 	{"[": "]"}	{"[": "]"}	1
+Special Characters: 	{"key ' key": "val ' val"}	{"key ' key": "val ' val"}	1
+Special Characters: 	{"key \" key": "val \" val"}	{"key \" key": "val \" val"}	1
+Special Characters: 	{"key \\ key": "val \\ val"}	{"key \\ key": "val \\ val"}	1
+Special Characters: 	{"key \\0 key": "val \n val"}	{"key \\0 key": "val \n val"}	1
+Special Characters: 	{"key \\Z key": "val ' val"}	{"key \\Z key": "val ' val"}	1
+Special Characters: 	{"key \b key": "val \b val"}	{"key \b key": "val \b val"}	1
+Special Characters: 	{"key \f key": "val \f val"}	{"key \f key": "val \f val"}	1
+Special Characters: 	{"key \n key": "val \n val"}	{"key \n key": "val \n val"}	1
+Special Characters: 	{"key \r key": "val \r val"}	{"key \r key": "val \r val"}	1
+Special Characters: 	{"key \t key": "val \t val"}	{"key \t key": "val \t val"}	1
+Special Characters: 	{"key1 and \n\"key2\"": "val1\t val2"}	{"key1 and \n\"key2\"": "val1\t val2"}	1
+Special Characters: 	{"{": "}"}	{"{": "}"}	1
+Special Characters: 	{"{": "}"}	{"{": "}"}	1
+Special String Cases: 	[""]	[""]	1
+Special String Cases: 	{"": ""}	{"": ""}	1
+Timestamp as RawValue	"2019-12-26 19:56:03.000000"	"2019-12-26 19:56:03.000000"	1
+UTF8 Characters: 	"Anel Husaković - test: đžšćč"	"Anel Husaković - test: đžšćč"	1
+UTF8 Characters: 	{"Name": "Anel Husaković - test: đžšćč"}	{"Name": "Anel Husaković - test: đžšćč"}	1
+UTF8 Characters: 	{"Person": "EMP", "details": {"Name": "Anel Husaković - test: đžšćč"}}	{"Person": "EMP", "details": {"Name": "Anel Husaković - test: đžšćč"}}	1
+UTF8 Characters: 	{"details": {"Name": "Anel Husaković - test: đžšćč"}, "\"Anel Husaković - test: đžšćč\"": "EMP"}	{"details": {"Name": "Anel Husaković - test: đžšćč"}, "\"Anel Husaković - test: đžšćč\"": "EMP"}	1
+#
+# A quick check that all rows match from the original MySQL Table.
+#
+select count(*) as 'Total_Number_of_Tests',
+sum(expected = actual) as 'Succesful_Tests'
+from mysql_json_test;
+Total_Number_of_Tests	Succesful_Tests
+100	100
+show create table mysql_json_test;
+Table	Create Table
+mysql_json_test	CREATE TABLE `mysql_json_test` (
+  `description` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
+  `expected` longtext COLLATE utf8mb4_unicode_ci DEFAULT NULL,
+  `actual` longtext CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
+show create table mysql_json_test_big;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.mysql_json_test_big` FORCE" or dump/reload to fix it!
+select * from mysql_json_test_big;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.mysql_json_test_big` FORCE" or dump/reload to fix it!
+#
+# This test checks the long format implementation of MySQL's JSON
+# Not printing the actual contents as they are not readable by a human,
+# just compare the strings, make sure they match.
+#
+alter table mysql_json_test_big force;
+select count(*) as 'Total_Number_of_Tests',
+sum(expected = actual) as 'Succesful_Tests',
+sum(JSON_VALID(actual)) as 'String_is_valid_JSON'
+from mysql_json_test_big;
+Total_Number_of_Tests	Succesful_Tests	String_is_valid_JSON
+1	1	1
+drop table tempty;
+drop table mysql_json_test;
+drop table mysql_json_test_big;

mysql-test/main/mysql_json_table_recreate.test

+--source include/have_utf8.inc
+
+--echo #
+--echo # The following test takes 2 tables containing a JSON column and attempts
+--echo # to repair them.
+--echo #
+--echo # The tables header is (Description, Expected, Actual), where description
+--echo # shows a brief description what the JSON value is testing in the MariaDB
+--echo # implementation. Expected is the longtext string and actual is the JSON
+--echo # column that needs to be converted to MariaDB's representation of
+--echo # LONGTEXT.
+--echo #
+
+
+call mtr.add_suppression("Table rebuild required");
+call mtr.add_suppression("is marked as crashed");
+call mtr.add_suppression("Checking");
+
+let $MYSQLD_DATADIR= `select @@datadir`;
+
+SET NAMES utf8;
+
+--copy_file std_data/mysql_json/tempty.frm $MYSQLD_DATADIR/test/tempty.frm
+--copy_file std_data/mysql_json/tempty.MYI $MYSQLD_DATADIR/test/tempty.MYI
+--copy_file std_data/mysql_json/tempty.MYD $MYSQLD_DATADIR/test/tempty.MYD
+
+--copy_file std_data/mysql_json/mysql_json_test.frm $MYSQLD_DATADIR/test/mysql_json_test.frm
+--copy_file std_data/mysql_json/mysql_json_test.MYI $MYSQLD_DATADIR/test/mysql_json_test.MYI
+--copy_file std_data/mysql_json/mysql_json_test.MYD $MYSQLD_DATADIR/test/mysql_json_test.MYD
+
+--copy_file std_data/mysql_json/mysql_json_test_big.frm $MYSQLD_DATADIR/test/mysql_json_test_big.frm
+--copy_file std_data/mysql_json/mysql_json_test_big.MYI $MYSQLD_DATADIR/test/mysql_json_test_big.MYI
+--copy_file std_data/mysql_json/mysql_json_test_big.MYD $MYSQLD_DATADIR/test/mysql_json_test_big.MYD
+
+--echo #
+--echo # Check that only ALTER TABLE ... FORCE is allowed on a MySQL 5.7 table
+--echo # with a JSON column.
+--echo #
+
+--error ER_TABLE_NEEDS_REBUILD
+show create table tempty;
+--error ER_TABLE_NEEDS_REBUILD
+select * from tempty;
+
+alter table tempty force;
+show create table tempty;
+
+--error ER_TABLE_NEEDS_REBUILD
+show create table mysql_json_test;
+--error ER_TABLE_NEEDS_REBUILD
+select * from mysql_json_test;
+
+--error ER_TABLE_NEEDS_REBUILD
+LOCK TABLES mysql_json_test WRITE;
+
+alter table mysql_json_test force;
+
+--sorted_result
+select description, expected, actual, expected = actual from mysql_json_test;
+
+--echo #
+--echo # A quick check that all rows match from the original MySQL Table.
+--echo #
+select count(*) as 'Total_Number_of_Tests',
+       sum(expected = actual) as 'Succesful_Tests'
+from mysql_json_test;
+
+show create table mysql_json_test;
+
+--error ER_TABLE_NEEDS_REBUILD
+show create table mysql_json_test_big;
+--error ER_TABLE_NEEDS_REBUILD
+select * from mysql_json_test_big;
+
+--echo #
+--echo # This test checks the long format implementation of MySQL's JSON
+--echo # Not printing the actual contents as they are not readable by a human,
+--echo # just compare the strings, make sure they match.
+--echo #
+alter table mysql_json_test_big force;
+
+select count(*) as 'Total_Number_of_Tests',
+       sum(expected = actual) as 'Succesful_Tests',
+       sum(JSON_VALID(actual)) as 'String_is_valid_JSON'
+from mysql_json_test_big;
+
+drop table tempty;
+drop table mysql_json_test;
+drop table mysql_json_test_big;

mysql-test/main/mysql_upgrade_mysql_json_datatype.result

+call mtr.add_suppression("Table rebuild required");
+call mtr.add_suppression("is marked as crashed");
+call mtr.add_suppression("Checking");
+SET NAMES utf8;
+set sql_mode="";
+install soname 'type_mysql_json.so';
+show create table tempty;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.tempty` FORCE" or dump/reload to fix it!
+show create table mysql_json_test;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.mysql_json_test` FORCE" or dump/reload to fix it!
+show create table mysql_json_test_big;
+ERROR HY000: Table rebuild required. Please do "ALTER TABLE `test.mysql_json_test_big` FORCE" or dump/reload to fix it!
+# Run mysql_upgrade to fix the tables containing JSON.
+Phase 1/7: Checking and upgrading mysql database
+Processing databases
+mysql
+mysql.column_stats                                 OK
+mysql.columns_priv                                 OK
+mysql.db                                           OK
+mysql.event                                        OK
+mysql.func                                         OK
+mysql.global_priv                                  OK
+mysql.gtid_slave_pos                               OK
+mysql.help_category                                OK
+mysql.help_keyword                                 OK
+mysql.help_relation                                OK
+mysql.help_topic                                   OK
+mysql.index_stats                                  OK
+mysql.innodb_index_stats                           OK
+mysql.innodb_table_stats                           OK
+mysql.plugin                                       OK
+mysql.proc                                         OK
+mysql.procs_priv                                   OK
+mysql.proxies_priv                                 OK
+mysql.roles_mapping                                OK
+mysql.servers                                      OK
+mysql.table_stats                                  OK
+mysql.tables_priv                                  OK
+mysql.time_zone                                    OK
+mysql.time_zone_leap_second                        OK
+mysql.time_zone_name                               OK
+mysql.time_zone_transition                         OK
+mysql.time_zone_transition_type                    OK
+mysql.transaction_registry                         OK
+Phase 2/7: Installing used storage engines... Skipped
+Phase 3/7: Fixing views
+mysql.user                                         OK
+Phase 4/7: Running 'mysql_fix_privilege_tables'
+Phase 5/7: Fixing table and database names
+Phase 6/7: Checking and upgrading tables
+Processing databases
+information_schema
+mtr
+mtr.global_suppressions                            OK
+mtr.test_suppressions                              OK
+performance_schema
+test
+test.mysql_json_test                               Needs upgrade
+test.mysql_json_test_big                           Needs upgrade
+test.tempty                                        Needs upgrade
+
+Repairing tables
+test.mysql_json_test                               OK
+test.mysql_json_test_big                           OK
+test.tempty                                        OK
+Phase 7/7: Running 'FLUSH PRIVILEGES'
+OK
+#
+# Now check if the table structure is correct and that the data
+# is still present.
+#
+show create table tempty;
+Table	Create Table
+tempty	CREATE TABLE `tempty` (
+  `t` longtext CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+show create table mysql_json_test;
+Table	Create Table
+mysql_json_test	CREATE TABLE `mysql_json_test` (
+  `description` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
+  `expected` longtext COLLATE utf8mb4_unicode_ci DEFAULT NULL,
+  `actual` longtext CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
+show create table mysql_json_test_big;
+Table	Create Table
+mysql_json_test_big	CREATE TABLE `mysql_json_test_big` (
+  `description` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
+  `expected` longtext COLLATE utf8mb4_unicode_ci DEFAULT NULL,
+  `actual` longtext CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
+select count(*) as 'Total_Number_of_Tests',
+sum(expected = actual) as 'Succesful_Tests',
+sum(JSON_VALID(actual)) as 'String_is_valid_JSON'
+from mysql_json_test;
+Total_Number_of_Tests	Succesful_Tests	String_is_valid_JSON
+100	100	100
+select count(*) as 'Total_Number_of_Tests',
+sum(expected = actual) as 'Succesful_Tests',
+sum(JSON_VALID(actual)) as 'String_is_valid_JSON'
+from mysql_json_test_big;
+Total_Number_of_Tests	Succesful_Tests	String_is_valid_JSON
+1	1	1
+drop table tempty;
+drop table mysql_json_test;
+drop table mysql_json_test_big;
+uninstall soname 'type_mysql_json.so';

mysql-test/main/mysql_upgrade_mysql_json_datatype.test

+-- source include/mysql_upgrade_preparation.inc
+-- source include/have_working_dns.inc
+-- source include/have_innodb.inc
+
+call mtr.add_suppression("Table rebuild required");
+call mtr.add_suppression("is marked as crashed");
+call mtr.add_suppression("Checking");
+
+let $MYSQLD_DATADIR= `select @@datadir`;
+SET NAMES utf8;
+
+--copy_file std_data/mysql_json/tempty.frm $MYSQLD_DATADIR/test/tempty.frm
+--copy_file std_data/mysql_json/tempty.MYI $MYSQLD_DATADIR/test/tempty.MYI
+--copy_file std_data/mysql_json/tempty.MYD $MYSQLD_DATADIR/test/tempty.MYD
+
+--copy_file std_data/mysql_json/mysql_json_test.frm $MYSQLD_DATADIR/test/mysql_json_test.frm
+--copy_file std_data/mysql_json/mysql_json_test.MYI $MYSQLD_DATADIR/test/mysql_json_test.MYI
+--copy_file std_data/mysql_json/mysql_json_test.MYD $MYSQLD_DATADIR/test/mysql_json_test.MYD
+
+--copy_file std_data/mysql_json/mysql_json_test_big.frm $MYSQLD_DATADIR/test/mysql_json_test_big.frm
+--copy_file std_data/mysql_json/mysql_json_test_big.MYI $MYSQLD_DATADIR/test/mysql_json_test_big.MYI
+--copy_file std_data/mysql_json/mysql_json_test_big.MYD $MYSQLD_DATADIR/test/mysql_json_test_big.MYD
+
+
+set sql_mode="";
+
+--eval install soname '$TYPE_MYSQL_JSON_SO'
+
+--error ER_TABLE_NEEDS_REBUILD
+show create table tempty;
+--error ER_TABLE_NEEDS_REBUILD
+show create table mysql_json_test;
+--error ER_TABLE_NEEDS_REBUILD
+show create table mysql_json_test_big;
+
+--echo # Run mysql_upgrade to fix the tables containing JSON.
+--exec $MYSQL_UPGRADE --force 2>&1
+
+--echo #
+--echo # Now check if the table structure is correct and that the data
+--echo # is still present.
+--echo #
+
+show create table tempty;
+show create table mysql_json_test;
+show create table mysql_json_test_big;
+
+select count(*) as 'Total_Number_of_Tests',
+sum(expected = actual) as 'Succesful_Tests',
+sum(JSON_VALID(actual)) as 'String_is_valid_JSON'
+from mysql_json_test;
+
+select count(*) as 'Total_Number_of_Tests',
+sum(expected = actual) as 'Succesful_Tests',
+sum(JSON_VALID(actual)) as 'String_is_valid_JSON'
+from mysql_json_test_big;
+
+drop table tempty;
+drop table mysql_json_test;
+drop table mysql_json_test_big;
+
+--eval uninstall soname '$TYPE_MYSQL_JSON_SO'
+--remove_file $MYSQLD_DATADIR/mysql_upgrade_info

plugin/type_mysql_json/CMakeLists.txt

+# Copyright (c) 2020, MariaDB Foundation.
+# 
+# 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
+
+MYSQL_ADD_PLUGIN(type_mysql_json
+                 mysql_json.cc type.cc
+                 MODULE_ONLY RECOMPILE_FOR_EMBEDDED)

plugin/type_mysql_json/mysql_json.cc

+/*
+  Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
+  Copyright (c) 2020 MariaDB Foundation
+
+
+   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 St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#include "mysql_json.h"
+#include "my_global.h"
+#include "compat56.h"
+#include "my_decimal.h"
+#include "sql_time.h"
+
+static void TIME_from_longlong_date_packed(MYSQL_TIME *ltime, longlong tmp)
+{
+  TIME_from_longlong_datetime_packed(ltime, tmp);
+  ltime->time_type= MYSQL_TIMESTAMP_DATE;
+}
+
+
+/*
+  Json values in MySQL comprises the standard set of JSON values plus a MySQL
+  specific set. A JSON number type is subdivided into int, uint, double and
+  decimal.
+
+  MySQL also adds four built-in date/time values: date, time, datetime and
+  timestamp. An additional opaque value can store any other MySQL type.
+*/
+
+enum JSONB_LITERAL_TYPES {
+  JSONB_NULL_LITERAL=      0x0,
+  JSONB_TRUE_LITERAL=      0x1,
+  JSONB_FALSE_LITERAL=     0x2,
+};
+
+/*
+  The size of offset or size fields in the small and the large storage
+  format for JSON objects and JSON arrays.
+*/
+static const uchar SMALL_OFFSET_SIZE= 2;
+static const uchar LARGE_OFFSET_SIZE= 4;
+
+/*
+  The size of key entries for objects when using the small storage
+  format or the large storage format. In the small format it is 4
+  bytes (2 bytes for key length and 2 bytes for key offset). In the
+  large format it is 6 (2 bytes for length, 4 bytes for offset).
+*/
+static const uchar KEY_ENTRY_SIZE_SMALL= (2 + SMALL_OFFSET_SIZE);
+static const uchar KEY_ENTRY_SIZE_LARGE= (2 + LARGE_OFFSET_SIZE);
+
+/*
+  The size of value entries for objects or arrays. When using the
+  small storage format, the entry size is 3 (1 byte for type, 2 bytes
+  for offset). When using the large storage format, it is 5 (1 byte
+  for type, 4 bytes for offset).
+*/
+static const uchar VALUE_ENTRY_SIZE_SMALL= (1 + SMALL_OFFSET_SIZE);
+static const uchar VALUE_ENTRY_SIZE_LARGE= (1 + LARGE_OFFSET_SIZE);
+
+/* The maximum number of nesting levels allowed in a JSON document. */
+static const uchar JSON_DOCUMENT_MAX_DEPTH= 150;
+
+/**
+  Read an offset or size field from a buffer. The offset could be either
+  a two byte unsigned integer or a four byte unsigned integer.
+
+  @param data  the buffer to read from
+  @param large tells if the large or small storage format is used; true
+               means read four bytes, false means read two bytes
+*/
+static inline size_t read_offset_or_size(const uchar *data, bool large)
+{
+  return large ? uint4korr(data) : uint2korr(data);
+}
+
+static inline size_t key_size(bool large)
+{
+  return large ? KEY_ENTRY_SIZE_LARGE : KEY_ENTRY_SIZE_SMALL;
+}
+
+static inline size_t value_size(bool large)
+{
+  return large ? VALUE_ENTRY_SIZE_LARGE : VALUE_ENTRY_SIZE_SMALL;
+}
+
+/**
+  Inlined values are a space optimization. The actual value is stored
+  instead of the offset pointer to the location where a non-inlined
+  value would be located.
+
+  @param[in] type   The type to check.
+  @param[in] large tells if the large or small storage format is used;
+*/
+static inline bool type_is_stored_inline(JSONB_TYPES type, bool large)
+{
+  return (type == JSONB_TYPE_INT16 ||
+          type == JSONB_TYPE_UINT16 ||
+          type == JSONB_TYPE_LITERAL ||
+          (large && (type == JSONB_TYPE_INT32 ||
+                     type == JSONB_TYPE_UINT32)));
+}
+
+/**
+  Read a variable length integer. A variable length integer uses the 8th bit in
+  each byte to mark if there are more bytes needed to store the integer. The
+  other 7 bits in the byte are used to store the actual integer's bits.
+
+  @param[in]  data         the buffer to read from
+  @param[in]  data_length  the maximum number of bytes to read from data
+  @param[out] length       the length that was read
+  @param[out] num          the number of bytes needed to represent the length
+  @return  false on success, true on error
+*/
+static inline bool read_variable_length(const uchar *data, size_t data_length,
+                                        size_t *length, size_t *num)
+{
+  /*
+    It takes five bytes to represent UINT_MAX32, which is the largest
+    supported length, so don't look any further.
+
+    Use data_length as max value to prevent segfault when reading a corrupted
+    JSON document.
+  */
+  const size_t MAX_BYTES= MY_MIN(data_length, 5);
+  size_t len= 0;
+  for (size_t i= 0; i < MAX_BYTES; i++)
+  {
+    /* Get the next 7 bits of the length. */
+    len|= (data[i] & 0x7f) << (7 * i);
+    if ((data[i] & 0x80) == 0)
+    {
+      /* The length shouldn't exceed 32 bits. */
+      if (len > UINT_MAX32)
+        return true;
+
+      /* This was the last byte. Return successfully. */
+      *num= i + 1;
+      *length= len;
+      return false;
+    }
+  }
+
+  /* No more available bytes. Return true to signal error. This implies a
+     corrupted JSON document. */
+  return true;
+}
+
+/**
+   JSON formatting in MySQL escapes a few special characters to prevent
+   ambiguity.
+*/
+static bool append_string_json(String *buffer, const uchar *data, size_t len)
+{
+  const uchar *last= data + len;
+  for (; data < last; data++)
+  {
+    const uchar c= *data;
+    switch (c) {
+    case '\\':
+      buffer->append("\\\\");
+      break;
+    case '\n':
+      buffer->append("\\n");
+      break;
+    case '\r':
+      buffer->append("\\r");
+      break;
+    case '"':
+      buffer->append("\\\"");
+      break;
+    case '\b':
+      buffer->append("\\b");
+      break;
+    case '\f':
+      buffer->append("\\f");
+      break;
+    case '\t':
+      buffer->append("\\t");
+      break;
+    default:
+      buffer->append(c);
+      break;
+    }
+  }
+  return false;
+}
+
+/*
+  Function used for JSON_OPAQUE type.
+*/
+static bool print_mysql_datetime_value(String *buffer, enum_field_types type,
+                                       const uchar *data, size_t len)
+{
+  if (len < 8)
+    return true;
+
+  MYSQL_TIME t;
+  switch (type)
+  {
+    case MYSQL_TYPE_TIME:
+      TIME_from_longlong_time_packed(&t, sint8korr(data));
+      break;
+    case MYSQL_TYPE_DATE:
+      TIME_from_longlong_date_packed(&t, sint8korr(data));
+      break;
+    case MYSQL_TYPE_DATETIME:
+    case MYSQL_TYPE_TIMESTAMP:
+      TIME_from_longlong_datetime_packed(&t, sint8korr(data));
+      break;
+    default:
+      DBUG_ASSERT(0);
+      return true;
+  }
+  /* Wrap all datetime strings within double quotes. */
+  buffer->append('\"');
+  buffer->reserve(MAX_DATE_STRING_REP_LENGTH);
+  buffer->length(buffer->length() +
+                 my_TIME_to_str(&t, const_cast<char *>(buffer->end()), 6));
+  buffer->append('\"');
+  return false;
+}
+
+static bool parse_mysql_scalar(String *buffer, size_t value_json_type,
+                               const uchar *data, size_t len)
+{
+  switch (value_json_type) {
+  case JSONB_TYPE_LITERAL:
+  {
+    if (len < 1)
+      return true;
+    switch (static_cast<JSONB_LITERAL_TYPES>(*data)) {
+    case JSONB_NULL_LITERAL:
+      return buffer->append("null");
+    case JSONB_TRUE_LITERAL:
+      return buffer->append("true");
+    case JSONB_FALSE_LITERAL:
+      return buffer->append("false");
+    default: /* Invalid literal constant, malformed JSON. */
+      return true;
+    }
+  }
+  case JSONB_TYPE_INT16:
+    return len < 2 || buffer->append_longlong(sint2korr(data));
+  case JSONB_TYPE_INT32:
+    return len < 4 || buffer->append_longlong(sint4korr(data));
+  case JSONB_TYPE_INT64:
+    return len < 8 || buffer->append_longlong(sint8korr(data));
+  case JSONB_TYPE_UINT16:
+    return len < 2 || buffer->append_ulonglong(uint2korr(data));
+  case JSONB_TYPE_UINT32:
+    return len < 4 || buffer->append_ulonglong(uint4korr(data));
+  case JSONB_TYPE_UINT64:
+    return len < 8 || buffer->append_ulonglong(uint8korr(data));
+  case JSONB_TYPE_DOUBLE:
+    if (len < 8)
+      return true;
+    buffer->reserve(FLOATING_POINT_BUFFER, 2 * FLOATING_POINT_BUFFER);
+    buffer->qs_append(reinterpret_cast<const double *>(data));
+    return false;
+  case JSONB_TYPE_STRING:
+  {
+    size_t string_length, store_bytes;
+
+    return read_variable_length(data, len, &string_length, &store_bytes) ||
+           len < store_bytes + string_length ||
+           buffer->append('"') ||
+           append_string_json(buffer, data + store_bytes, string_length) ||
+           buffer->append('"');
+  }
+  case JSONB_TYPE_OPAQUE:
+  {
+    /* The field_type maps directly to enum_field_types. */
+    const uchar type_value= *data;
+    const enum_field_types field_type= static_cast<enum_field_types>(type_value);
+
+    size_t blob_length, length_bytes;
+    const uchar *blob_start;
+
+    if (read_variable_length(data + 1, len, &blob_length, &length_bytes) ||
+        len < length_bytes + blob_length)
+      return true;
+    blob_start= data + length_bytes + 1;
+
+    switch (field_type) {
+    case MYSQL_TYPE_TIME:
+    case MYSQL_TYPE_DATE:
+    case MYSQL_TYPE_DATETIME:
+    case MYSQL_TYPE_TIMESTAMP:
+      return print_mysql_datetime_value(buffer, field_type,
+                                        blob_start, blob_length);
+    case MYSQL_TYPE_NEWDECIMAL:
+    {
+      /* Expect at least two bytes, which contain precision and scale. */
+      if (blob_length < 2)
+        return true;
+
+      const int precision= blob_start[0];
+      const int scale= blob_start[1];
+
+      my_decimal d;
+
+      /* The decimal value is encoded after the two prec/scale bytes. */
+      const size_t dec_size= my_decimal_get_binary_size(precision, scale);
+      if (dec_size != blob_length - 2 ||
+          binary2my_decimal(E_DEC_ERROR,
+                            reinterpret_cast<const uchar *>(blob_start + 2),
+                            &d, precision, scale) != E_DEC_OK)
+        return true;
+
+      if (d.to_string_native(buffer, 0, 0, ' ', E_DEC_ERROR) != E_DEC_OK)
+        return true;
+      return false;
+    }
+    default:
+    {
+      /* Any other MySQL type is presented as a base64 encoded string. */
+      if (buffer->append("\"base64:type") ||
+          buffer->append_longlong(field_type) ||
+          buffer->append(':'))
+        return true;
+
+      const size_t needed= my_base64_needed_encoded_length(
+          static_cast<int>(blob_length));
+      if (buffer->reserve(needed) ||
+          my_base64_encode(blob_start, blob_length,
+                           const_cast<char*>(buffer->end())))
+        return true;
+      /* -1 to override the null terminator from my_base64_encode */
+      DBUG_ASSERT(*(buffer->end() + needed) == '\0');
+      buffer->length(buffer->length() + needed - 1);
+      return buffer->append('"');
+    }
+    }
+  }
+  default:
+    return true;
+  }
+}
+
+
+/**
+  Read a value from a JSON Object or Array, given the position of it.
+  This function handles both inlined values as well as values stored at
+  an offset.
+
+  @param[out] buffer            Where to print the results.
+  @param[in] data               The raw binary data of the Object or Array.
+  @param[in] len                The length of the binary data.
+  @param[in] value_type_offset  Where the type of the value is stored.
+  @param[in] large              true if the large storage format is used;
+  @param[in] depth              How deep the JSON object is in the hierarchy.
+*/
+static bool parse_mysql_scalar_or_value(String *buffer, const uchar *data,
+                                        size_t len, size_t value_type_offset,
+                                        bool large, size_t depth)
+{
+  /* Get the type of the value stored at the key. */
+  const JSONB_TYPES value_type=
+    static_cast<JSONB_TYPES>(data[value_type_offset]);
+
+  if (type_is_stored_inline(value_type, large))
+  {
+    const size_t value_start = value_type_offset + 1;
+    if (parse_mysql_scalar(buffer, value_type, data + value_start,
+                           len - value_start))
+      return true;
+  }
+  else
+  {
+    /* The offset to where the value is stored is relative to the start
+       of the Object / Array */
+    const size_t value_start= read_offset_or_size(
+                                      data + value_type_offset + 1, large);
+    if (parse_mysql_json_value(buffer, value_type, data + value_start,
+                               len - value_start, depth))
+      return true;
+  }
+  return false;
+}
+
+static bool parse_array_or_object(String *buffer, const uchar *data, size_t len,
+                                  bool handle_as_object, bool large,
+                                  size_t depth)
+{
+  if (++depth > JSON_DOCUMENT_MAX_DEPTH)
+    return true;
+
+  /*
+    Make sure the document is long enough to contain the two length fields
+    (both number of elements or members, and number of bytes).
+  */
+  const size_t offset_size= large ? LARGE_OFFSET_SIZE : SMALL_OFFSET_SIZE;
+  /* The length has to be at least double offset size (header). */
+  if (len < 2 * offset_size)
+    return true;
+
+
+  /*
+     Every JSON Object or Array contains two numbers in the header:
+     - The number of elements in the Object / Array (Keys)
+     - The total number of bytes occupied by the JSON Object / Array, including
+       the two numbers in the header.
+     Depending on the Object / Array type (small / large) the numbers are stored
+     in 2 bytes or 4 bytes each.
+  */
+  const size_t element_count= read_offset_or_size(data, large);
+  const size_t bytes= read_offset_or_size(data + offset_size, large);
+
+  /* The value can't have more bytes than what's available in the buffer. */
+  if (bytes > len)
+    return true;
+
+  if (buffer->append(handle_as_object ? '{' : '['))
+    return true;
+
+
+  for (size_t i= 0; i < element_count; i++)
+  {
+    if (handle_as_object)
+    {
+      /*
+        The JSON Object is stored as a header part and a data part.
+        Header consists of:
+        - two length fields,
+        - an array of pointers to keys.
+        - an array of tuples (type, pointer to values)
+          * For certain types, the pointer to values is replaced by the actual
+            value. (see type_is_stored_inline)
+        Data consists of:
+        - All Key data, in order
+        - All Value data, in order
+      */
+      const size_t key_offset= 2 * offset_size + i * key_size(large);
+      const size_t key_start= read_offset_or_size(data + key_offset, large);
+      /* The length of keys is always stored in 2 bytes (large == false) */
+      const size_t key_len= read_offset_or_size(
+                                   data + key_offset + offset_size, false);
+
+      const size_t value_type_offset=(2 * offset_size +
+                                      element_count * key_size(large) +
+                                      i * value_size(large));
+
+      /* First print the key. */
+      if (buffer->append('"') ||
+          append_string_json(buffer, data + key_start, key_len) ||
+          buffer->append("\": "))
+      {
+        return true;
+      }
+
+      /* Then print the value. */
+      if (parse_mysql_scalar_or_value(buffer, data, bytes, value_type_offset,
+                                      large, depth))
+        return true;
+    }
+    else
+    {
+      /*
+         Arrays do not have the keys vector and its associated data.
+         We jump straight to reading values.
+      */
+      const size_t value_type_offset= 2 * offset_size + value_size(large) * i;
+
+      if (parse_mysql_scalar_or_value(buffer, data, bytes, value_type_offset,
+                                      large, depth))
+        return true;
+    }
+
+    if (i != element_count - 1 && buffer->append(", "))
+      return true;
+  }
+
+  return buffer->append(handle_as_object ? '}' : ']');
+}
+
+/**
+  Check the first byte of data which is the enum structure and based on it
+  perform parsing of object or array where each can have small or large
+  representation.
+
+  @param[out] buffer            Where to print the results.
+  @param[in] type               Type of value {object, array, scalar}.
+  @param[in] data               Raw data for parsing.
+  @param[in] length             Length of data.
+  @param[in] depth              Depth size.
+*/
+bool parse_mysql_json_value(String *buffer, JSONB_TYPES type, const uchar *data,
+                            size_t len, size_t depth)
+{
+  const bool IS_OBJECT=true, IS_LARGE=true;
+  switch (type) {
+  case JSONB_TYPE_SMALL_OBJECT:
+    return parse_array_or_object(buffer, data, len, IS_OBJECT, !IS_LARGE, depth);
+  case JSONB_TYPE_LARGE_OBJECT:
+    return parse_array_or_object(buffer, data, len, IS_OBJECT, IS_LARGE, depth);
+  case JSONB_TYPE_SMALL_ARRAY:
+    return parse_array_or_object(buffer, data, len, !IS_OBJECT, !IS_LARGE, depth);
+  case JSONB_TYPE_LARGE_ARRAY:
+    return parse_array_or_object(buffer, data, len, !IS_OBJECT, IS_LARGE, depth);
+  default:
+    return parse_mysql_scalar(buffer, type, data, len);
+  }
+}

plugin/type_mysql_json/mysql_json.h

+/*
+  Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
+  Copyright (c) 2020 MariaDB Foundation
+
+
+   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 St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#ifndef MYSQL_JSON_INCLUDED
+#define MYSQL_JSON_INCLUDED
+
+#include "my_global.h"
+#include "sql_string.h"                         // String
+
+enum JSONB_TYPES {
+  JSONB_TYPE_SMALL_OBJECT= 0x0,
+  JSONB_TYPE_LARGE_OBJECT= 0x1,
+  JSONB_TYPE_SMALL_ARRAY=  0x2,
+  JSONB_TYPE_LARGE_ARRAY=  0x3,
+  JSONB_TYPE_LITERAL=      0x4,
+  JSONB_TYPE_INT16=        0x5,
+  JSONB_TYPE_UINT16=       0x6,
+  JSONB_TYPE_INT32=        0x7,
+  JSONB_TYPE_UINT32=       0x8,
+  JSONB_TYPE_INT64=        0x9,
+  JSONB_TYPE_UINT64=       0xA,
+  JSONB_TYPE_DOUBLE=       0xB,
+  JSONB_TYPE_STRING=       0xC,
+  JSONB_TYPE_OPAQUE=       0xF
+};
+
+bool parse_mysql_json_value(String *buffer, JSONB_TYPES type, const uchar *data,
+                            size_t len, size_t depth);
+#endif  /* MYSQL_JSON_INCLUDED */

plugin/type_mysql_json/type.cc

+/*
+   Copyright (c) 2020 MariaDB Foundation
+
+   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 St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#include <mysql/plugin_data_type.h>
+#include <my_global.h>
+#include <sql_type.h>
+#include <field.h>
+#include <mysqld_error.h>
+#include "mysql_json.h"
+
+static const LEX_CSTRING empty_clex_str= {"", 0};
+
+class Type_handler_mysql_json: public Type_handler_blob
+{
+public:
+  Field *make_conversion_table_field(MEM_ROOT *, TABLE *, uint, const Field *)
+    const override;
+  const Type_collection *type_collection() const override;
+  Field *make_table_field_from_def(TABLE_SHARE *, MEM_ROOT *,
+                                   const LEX_CSTRING *, const Record_addr &,
+                                   const Bit_addr &,
+                                   const Column_definition_attributes *,
+                                   uint32) const override;
+  Field *make_table_field(MEM_ROOT *, const LEX_CSTRING *,
+                          const Record_addr &, const Type_all_attributes &,
+                          TABLE_SHARE *) const override;
+};
+
+Type_handler_mysql_json type_handler_mysql_json;
+
+
+class Field_mysql_json: public Field_blob
+{
+public:
+  Field_mysql_json(uchar *ptr_arg, uchar *null_ptr_arg,
+                   uchar null_bit_arg, enum utype unireg_check_arg,
+                   const LEX_CSTRING *field_name_arg, TABLE_SHARE *share,
+                   uint blob_pack_length, const DTCollation &collation)
+    : Field_blob(ptr_arg, null_ptr_arg, null_bit_arg, unireg_check_arg,
+                 field_name_arg, share, blob_pack_length,
+                 &my_charset_utf8mb4_bin)
+  {}
+
+  String *val_str(String *val_buffer, String *val_str);
+  const Type_handler *type_handler() const { return &type_handler_mysql_json; }
+  bool parse_mysql(String *dest, const char *data, size_t length) const;
+  bool send(Protocol *protocol) { return Field::send(protocol); }
+  void sql_type(String &s) const
+  { s.set_ascii(STRING_WITH_LEN("json /* MySQL 5.7 */")); }
+  /* this will make ALTER TABLE to consider it different from built-in field */
+  Compression_method *compression_method() const { return (Compression_method*)1; }
+};
+
+Field *Type_handler_mysql_json::make_conversion_table_field(MEM_ROOT *root,
+                    TABLE *table, uint metadata, const Field *target) const
+{
+  uint pack_length= metadata & 0x00ff;
+  if (pack_length < 1 || pack_length > 4)
+    return NULL; // Broken binary log?
+  return new (root)
+         Field_mysql_json(NULL, (uchar *) "", 1, Field::NONE, &empty_clex_str,
+                          table->s, pack_length, target->charset());
+}
+
+Field *Type_handler_mysql_json::make_table_field_from_def(TABLE_SHARE *share,
+                 MEM_ROOT *root, const LEX_CSTRING *name,
+                 const Record_addr &addr, const Bit_addr &bit,
+                 const Column_definition_attributes *attr, uint32 flags) const
+{
+  return new (root) Field_mysql_json(addr.ptr(), addr.null_ptr(),
+                 addr.null_bit(), attr->unireg_check, name, share,
+                 attr->pack_flag_to_pack_length(), attr->charset);
+}
+
+
+Field *Type_handler_mysql_json::make_table_field(MEM_ROOT *root,
+                 const LEX_CSTRING *name, const Record_addr &addr,
+                 const Type_all_attributes &attr, TABLE_SHARE *share) const
+{
+  return new (root) Field_mysql_json(addr.ptr(), addr.null_ptr(),
+                 addr.null_bit(), Field::NONE, name, share, 2, attr.collation);
+}
+
+
+String *Field_mysql_json::val_str(String *val_buffer, String *val_ptr)
+{
+  String *raw_value= Field_blob::val_str(val_buffer, val_ptr);
+  String data;
+
+  data.copy(*raw_value);
+
+  val_ptr->length(0);
+  if (parse_mysql(val_ptr, data.ptr(), data.length()))
+  {
+    val_ptr->length(0);
+    my_printf_error(ER_UNKNOWN_ERROR,
+        "Error parsing MySQL JSON format, please dump this table from MySQL "
+        "and then restore it to be able to use it in MariaDB.", MYF(0));
+  }
+  return val_ptr;
+}
+
+bool Field_mysql_json::parse_mysql(String *dest,
+                                   const char *data, size_t length) const
+{
+  if (!data)
+    return false;
+
+  /* Each JSON blob must start with a type specifier. */
+  if (length < 2)
+    return true;
+
+  if (parse_mysql_json_value(dest, static_cast<JSONB_TYPES>(data[0]),
+                             reinterpret_cast<const uchar*>(data) + 1,
+                             length - 1, 0))
+    return true;
+
+  return false;
+}
+
+class Type_collection_mysql_json: public Type_collection
+{
+public:
+  const Type_handler *aggregate_for_result(const Type_handler *a,
+                                           const Type_handler *b)
+                                           const override
+  {
+    if (a == b)
+      return a;
+    return NULL;
+  }
+
+  const Type_handler *aggregate_for_min_max(const Type_handler *a,
+                                            const Type_handler *b)
+                                            const override
+  {
+    return aggregate_for_result(a, b);
+  }
+
+  const Type_handler *aggregate_for_comparison(const Type_handler *a,
+                                               const Type_handler *b)
+                                               const override
+  {
+    return aggregate_for_result(a, b);
+  }
+
+  const Type_handler *aggregate_for_num_op(const Type_handler *a,
+                                           const Type_handler *b)
+                                           const override
+  {
+    return NULL;
+  }
+
+  const Type_handler *handler_by_name(const LEX_CSTRING &name) const override
+  {
+    if (type_handler_mysql_json.name().eq(name))
+      return &type_handler_mysql_json;
+    return NULL;
+  }
+};
+
+const Type_collection *Type_handler_mysql_json::type_collection() const
+{
+  static Type_collection_mysql_json type_collection_mysql_json;
+  return &type_collection_mysql_json;
+}
+
+static struct st_mariadb_data_type plugin_descriptor_type_mysql_json=
+{
+  MariaDB_DATA_TYPE_INTERFACE_VERSION,
+  &type_handler_mysql_json
+};
+
+maria_declare_plugin(type_mysql_json)
+{
+  MariaDB_DATA_TYPE_PLUGIN,
+  &plugin_descriptor_type_mysql_json,
+  "MYSQL_JSON",
+  "Anel Husaković, Vicențiu Ciorbaru",
+  "Data type MYSQL_JSON",
+  PLUGIN_LICENSE_GPL,
+  0,
+  0,
+  0x0001,
+  NULL,
+  NULL,
+  "0.1",
+  MariaDB_PLUGIN_MATURITY_ALPHA
+}
+maria_declare_plugin_end;

sql/table.cc

@@ -2367,7 +2367,8 @@ int TABLE_SHARE::init_from_binary_frm_image(THD *thd, bool write,
 	comment_pos+=   comment_length;
       }
 
-      if ((uchar) strpos[13] == (uchar) MYSQL_TYPE_VIRTUAL)
+      if ((uchar) strpos[13] == (uchar) MYSQL_TYPE_VIRTUAL
+          && likely(share->mysql_version >= 100000))
       {
         /*
           MariaDB version 10.0 version.
@@ -2417,7 +2418,18 @@ int TABLE_SHARE::init_from_binary_frm_image(THD *thd, bool write,
         interval_nr=  (uint) strpos[12];
         enum_field_types field_type= (enum_field_types) strpos[13];
         if (!(handler= Type_handler::get_handler_by_real_type(field_type)))
-          goto err; // Not supported field type
+        {
+          if (field_type == 245 &&
+              share->mysql_version >= 50700) // a.k.a MySQL 5.7 JSON
+          {
+            share->incompatible_version|= HA_CREATE_USED_ENGINE;
+            const LEX_CSTRING mysql_json{STRING_WITH_LEN("MYSQL_JSON")};
+            handler= Type_handler::handler_by_name_or_error(thd, mysql_json);
+          }
+
+          if (!handler)
+            goto err; // Not supported field type
+        }
         handler= handler->type_handler_frm_unpack(strpos);
         if (handler->Column_definition_attributes_frm_unpack(&attr, share,
                                                              strpos,