[jdbc] Use `TEXT` for fields instead of VARCHAR (#910)

jdbc/src/main/java/com/yahoo/ycsb/db/JdbcDBClient.java

@@ -39,7 +39,7 @@ import com.yahoo.ycsb.db.flavors.DBFlavor;
  *
  * <br>
  * This interface expects a schema <key> <field1> <field2> <field3> ... All
- * attributes are of type VARCHAR. All accesses are through the primary key.
+ * attributes are of type TEXT. All accesses are through the primary key.
  * Therefore, only one index on the primary key is needed.
  */
 public class JdbcDBClient extends DB {

jdbc/src/main/java/com/yahoo/ycsb/db/JdbcDBCreateTable.java

@@ -73,7 +73,7 @@ public final class JdbcDBCreateTable {
       for (int idx = 0; idx < fieldcount; idx++) {
         sql.append(", FIELD");
         sql.append(idx);
-        sql.append(" VARCHAR");
+        sql.append(" TEXT");
       }
       sql.append(");");