MDEV-28533: CONNECT engine does not quote columns involved in WHERE clause (#2263)

storage/connect/ha_connect.cc

@@ -3073,6 +3073,8 @@ PCFIL ha_connect::CheckCond(PGLOBAL g, PCFIL filp, const Item *cond)
 
       if ((iscol= args[i]->type() == COND::FIELD_ITEM)) {
         const char *fnm;
+        char buf[MAX_FIELD_WIDTH];
+        String strColumn(buf, sizeof(buf), system_charset_info);
         ha_field_option_struct *fop;
         Item_field *pField= (Item_field *)args[i];
 
@@ -3098,8 +3100,14 @@ PCFIL ha_connect::CheckCond(PGLOBAL g, PCFIL filp, const Item *cond)
 					return NULL;
 				} else {
 					bool h;
-
 					fnm= filp->Chk(pField->field->field_name.str, &h);
+          if (tty == TYPE_AM_MYSQL && !(x || ismul))
+          {
+            strColumn.length(0);
+            strColumn.qs_append(STRING_WITH_LEN("`"));
+            strColumn.qs_append(fnm);
+            strColumn.append(STRING_WITH_LEN("`"));
+          }
 
 					if (h && i && !ishav)
 						return NULL;			// Having should be	col VOP arg
@@ -3113,9 +3121,11 @@ PCFIL ha_connect::CheckCond(PGLOBAL g, PCFIL filp, const Item *cond)
           htrc("Field name=%s\n", pField->field->field_name.str);
           htrc("Field type=%d\n", pField->field->type());
           htrc("Field_type=%d\n", args[i]->field_type());
-          } // endif trace
-
-        strcat((ishav ? havg : body), fnm);
+        } // endif trace
+        if (tty == TYPE_AM_MYSQL && !(x || ismul))
+          strcat((ishav ? havg : body), strColumn.ptr());
+        else
+          strcat((ishav ? havg : body), fnm);
       } else if (args[i]->type() == COND::FUNC_ITEM) {
         if (tty == TYPE_AM_MYSQL) {
           if (!CheckCond(g, filp, args[i]))

storage/connect/mysql-test/connect/r/mysql.result

@@ -304,5 +304,27 @@ INSERT INTO t2 VALUES (10),(20),(30),(40);
 DROP TABLE t2;
 DROP TABLE t1;
 #
+# MDEV-28533 CONNECT engine does not quote columns involved in WHERE clause
+#
+CREATE TABLE t1 (id int, `spaced col` varchar(10),`nospace` varchar(10));
+insert into t1 values (1,1,'x1'),(2,'C-003','x2');
+SELECT * from t1;
+id	spaced col	nospace
+1	1	x1
+2	C-003	x2
+CREATE TABLE t2 (id int, `spaced col` varchar(10), `nospace` varchar(10)) ENGINE=CONNECT TABLE_TYPE=MYSQL DBNAME='test' TABNAME='t1' OPTION_LIST='host=localhost,user=root,port=PORT';
+SELECT * from t2;
+id	spaced col	nospace
+1	1	x1
+2	C-003	x2
+SELECT `id` FROM t2 WHERE t2.`nospace` = 'x1';
+id
+1
+SELECT `id` FROM t2 WHERE t2.`spaced col` = 'C-003';
+id
+2
+DROP TABLE t1;
+DROP TABLE t2;
+#
 # End of 10.3 tests
 #

storage/connect/mysql-test/connect/t/mysql.test

@@ -483,6 +483,26 @@ INSERT INTO t2 VALUES (10),(20),(30),(40);
 DROP TABLE t2;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-28533 CONNECT engine does not quote columns involved in WHERE clause
+--echo #
+
+CREATE TABLE t1 (id int, `spaced col` varchar(10),`nospace` varchar(10));
+insert into t1 values (1,1,'x1'),(2,'C-003','x2');
+
+SELECT * from t1;
+
+--replace_result $PORT PORT
+--eval CREATE TABLE t2 (id int, `spaced col` varchar(10), `nospace` varchar(10)) ENGINE=CONNECT TABLE_TYPE=MYSQL DBNAME='test' TABNAME='t1' OPTION_LIST='host=localhost,user=root,port=$PORT'
+
+SELECT * from t2;
+SELECT `id` FROM t2 WHERE t2.`nospace` = 'x1';
+SELECT `id` FROM t2 WHERE t2.`spaced col` = 'C-003';
+
+
+DROP TABLE t1;
+DROP TABLE t2;
+
 --echo #
 --echo # End of 10.3 tests
 --echo #