The custom function dblink is listed in select in sql
The original extraction method is to package the data in the b library oci, put the data into the local disk of the middleware, and then load it into the a library through sqlldr. SQL is as follows:
select column_name1,function_name(column_name2) from table_name;
This sql is executed in library b. The b library table_name has tens of millions of rows of data.
Then change this method to dblink mode, and the table name and function name appearing in sql need to be added with dblink. A library executes sql as follows:
insert into a.table_name select column_name1, function_name@dblink(column_name2) from b.table_name@dblink This will cause performance problems. For each row of data returned, you have to go to b library to call a custom function. You can consider creating the function locally.
