Fix issue while inserting to enum value column.

While binding value in mysql_bind_sql_var(), we map PG type id to the
corresponding MySQL type in mysql_from_pgtyp() and then appropriately
create a buffer containing the value.  However, this logic only cares
about the built-in types and as enum has a user-defined type, it
resulted in an error.  To support bind for enum values, if the type
is an enum then use ANYENUMOID builtin type and convert the value to
string form using its output function.  MySQL accepts enum value in
string form so we map ANYENUMOID to MYSQL_TYPE_STRING too.

Note that we set sql_mode to ANSI_QUOTES while creating a connection
with MySQL that causes to insert an empty string at MySQL side for the
enum column when the given enum value is not present.  And thus, to
select from such a table having enum value as '', we need to create an
enum type at Postgres side with all valid values and ''.  Also, if we
try to insert an enum value which is not present in PG's enum type,
then PG's sanity check itself throws an error.

FDW-169, Suraj Kharage, reviewed by Jeevan Ladhe.

Author: jeevanchalke

expected/select.out

@@ -1033,6 +1033,57 @@ SELECT t1.c1, t2.c1
 
 DELETE FROM f_test_tbl2 WHERE c1 IN (50, 60);
 ALTER SERVER mysql_svr OPTIONS (SET use_remote_estimate 'false');
+-- FDW-169: Insert/Update/Delete on enum column.
+INSERT INTO f_enum_t1
+  VALUES (1, 'small'), (2, 'medium'), (3, 'medium'), (4, 'small');
+SELECT * FROM f_enum_t1 WHERE id = 4;
+ id | size  
+----+-------
+  4 | small
+(1 row)
+
+UPDATE f_enum_t1 SET size = 'large' WHERE id = 4;
+SELECT * FROM f_enum_t1 WHERE id = 4;
+ id | size  
+----+-------
+  4 | large
+(1 row)
+
+DELETE FROM f_enum_t1 WHERE size = 'large';
+SELECT * FROM f_enum_t1 WHERE id = 4;
+ id | size 
+----+------
+(0 rows)
+
+-- Negative scenarios for ENUM handling.
+-- Test that if we insert the ENUM value which is not present on MySQL side,
+-- but present on Postgres side.
+DROP FOREIGN TABLE f_enum_t1;
+DROP TYPE size_t;
+-- Create the type with extra enum values.
+CREATE TYPE size_t AS enum('small', 'medium', 'large', 'largest', '');
+CREATE FOREIGN TABLE f_enum_t1(id int, size size_t)
+  SERVER mysql_svr OPTIONS (dbname 'mysql_fdw_regress', table_name 'enum_t1');
+-- If we insert the enum value which is not present on MySQL side then it
+-- inserts empty string in ANSI_QUOTES sql_mode, so verify that.
+INSERT INTO f_enum_t1 VALUES (4, 'largest');
+SELECT * from f_enum_t1;
+ id |  size  
+----+--------
+  1 | small
+  2 | medium
+  3 | medium
+  4 | 
+(4 rows)
+
+DELETE FROM f_enum_t1 WHERE size = '';
+-- Postgres should throw an error as the value which we are inserting for enum
+-- column is not present in enum on Postgres side, no matter whether it is
+-- present on MySQL side or not. PG's sanity check itself throws an error.
+INSERT INTO f_enum_t1 VALUES (4, 'big');
+ERROR:  invalid input value for enum size_t: "big"
+LINE 1: INSERT INTO f_enum_t1 VALUES (4, 'big');
+                                         ^
 -- FDW-155: Enum data type can be handled correctly in select statements on
 -- foreign table.
 SELECT * FROM f_enum_t1 WHERE size = 'medium' ORDER BY id;
@@ -1251,6 +1302,7 @@ DROP VIEW mul_tbl_view;
 DELETE FROM f_test_tbl1;
 DELETE FROM f_test_tbl2;
 DELETE FROM f_numbers;
+DELETE FROM f_enum_t1;
 DROP FOREIGN TABLE f_test_tbl1;
 DROP FOREIGN TABLE f_test_tbl2;
 DROP FOREIGN TABLE f_numbers;

mysql_init.sh

@@ -41,7 +41,6 @@ mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress -e
 mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress1 -e "CREATE TABLE student (stu_id int PRIMARY KEY, stu_name text, stu_dept int);"
 mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress1 -e "CREATE TABLE numbers (a int, b varchar(255));"
 mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress -e "CREATE TABLE enum_t1 (id int PRIMARY KEY, size ENUM('small', 'medium', 'large'));"
-mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress -e "INSERT INTO enum_t1 VALUES (1, 'small'),(2, 'medium'),(3, 'medium');"
 mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress1 -e "CREATE TABLE student1 (stu_id varchar(10) PRIMARY KEY, stu_name text, stu_dept int);"
 mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress -e "CREATE TABLE enum_t2 (id int PRIMARY KEY, size ENUM('S', 'M', 'L'));"
 mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -P $MYSQL_PORT -D mysql_fdw_regress -e "INSERT INTO enum_t2 VALUES (10, 'S'),(20, 'M'),(30, 'M');"

mysql_query.c

@@ -144,6 +144,7 @@ mysql_from_pgtyp(Oid type)
 		case VARCHAROID:
 		case TEXTOID:
 		case JSONOID:
+		case ANYENUMOID:
 			return MYSQL_TYPE_STRING;
 		case NAMEOID:
 			return MYSQL_TYPE_STRING;
@@ -188,6 +189,13 @@ mysql_bind_sql_var(Oid type, int attnum, Datum value, MYSQL_BIND *binds,
 	if (*isnull)
 		return;
 
+	/*
+	 * If type is an enum, use ANYENUMOID.  We will send string containing the
+	 * enum value to the MySQL.
+	 */
+	if (type_is_enum(type))
+		type = ANYENUMOID;
+
 	/* Assign the buffer type if value is not null */
 	binds[attnum].buffer_type = mysql_from_pgtyp(type);
 
@@ -269,6 +277,7 @@ mysql_bind_sql_var(Oid type, int attnum, Datum value, MYSQL_BIND *binds,
 		case VARCHAROID:
 		case TEXTOID:
 		case JSONOID:
+		case ANYENUMOID:
 			{
 				char	   *outputString = NULL;
 				Oid			outputFunctionId = InvalidOid;

sql/select.sql

@@ -260,6 +260,36 @@ SELECT t1.c1, t2.c1
 DELETE FROM f_test_tbl2 WHERE c1 IN (50, 60);
 ALTER SERVER mysql_svr OPTIONS (SET use_remote_estimate 'false');
 
+-- FDW-169: Insert/Update/Delete on enum column.
+INSERT INTO f_enum_t1
+  VALUES (1, 'small'), (2, 'medium'), (3, 'medium'), (4, 'small');
+SELECT * FROM f_enum_t1 WHERE id = 4;
+UPDATE f_enum_t1 SET size = 'large' WHERE id = 4;
+SELECT * FROM f_enum_t1 WHERE id = 4;
+DELETE FROM f_enum_t1 WHERE size = 'large';
+SELECT * FROM f_enum_t1 WHERE id = 4;
+
+-- Negative scenarios for ENUM handling.
+-- Test that if we insert the ENUM value which is not present on MySQL side,
+-- but present on Postgres side.
+DROP FOREIGN TABLE f_enum_t1;
+DROP TYPE size_t;
+-- Create the type with extra enum values.
+CREATE TYPE size_t AS enum('small', 'medium', 'large', 'largest', '');
+CREATE FOREIGN TABLE f_enum_t1(id int, size size_t)
+  SERVER mysql_svr OPTIONS (dbname 'mysql_fdw_regress', table_name 'enum_t1');
+
+-- If we insert the enum value which is not present on MySQL side then it
+-- inserts empty string in ANSI_QUOTES sql_mode, so verify that.
+INSERT INTO f_enum_t1 VALUES (4, 'largest');
+SELECT * from f_enum_t1;
+DELETE FROM f_enum_t1 WHERE size = '';
+
+-- Postgres should throw an error as the value which we are inserting for enum
+-- column is not present in enum on Postgres side, no matter whether it is
+-- present on MySQL side or not. PG's sanity check itself throws an error.
+INSERT INTO f_enum_t1 VALUES (4, 'big');
+
 -- FDW-155: Enum data type can be handled correctly in select statements on
 -- foreign table.
 SELECT * FROM f_enum_t1 WHERE size = 'medium' ORDER BY id;
@@ -337,6 +367,7 @@ DROP VIEW mul_tbl_view;
 DELETE FROM f_test_tbl1;
 DELETE FROM f_test_tbl2;
 DELETE FROM f_numbers;
+DELETE FROM f_enum_t1;
 DROP FOREIGN TABLE f_test_tbl1;
 DROP FOREIGN TABLE f_test_tbl2;
 DROP FOREIGN TABLE f_numbers;