Sending the whole map over a network would quickly overburden a wireless network. This is especially the case in volumetric 3D maps due to the added third dimension. Since the memory footprint of the data scales indefinitely with the resolution and size of the environment, these maps can become quite large. Usually these maps have to be transferred between different systems, like for example in a multi robot setup or if a operator needs access to the data on a remote control room. To utilize the increased mobility of these robots, autonomous navigation algorithms require fast and accurate volumetric maps, generated by the sensors of the robot. You can check the SQL statement generated by Oracle Database by explaining the statement and querying the OTHER column of the explain plan table for each REMOTE operation.In recent times, the distribution of mobile walking robots has increased sharply due to their high availability. If there are indexes on the remote table that can be used, these indexes are used in a WHERE clause predicate to reduce the number of rows retrieved across the network.
#Remote mapper full#
A full table scan is when all the data in the remote table across the network without any filtering (for example, SELECT * FROM EMP) is retrieved.įull table scans are expensive and, therefore, Oracle noun attempts to avoid them. The SELECT statements affected by this rule are executed by retrieving all the necessary data through a remote SELECT operation, and processing the unsupported operator or construct locally using the SQL engine.Ī remote SELECT operation is the operation that retrieves rows from a remote table, as opposed to an operation that retrieves data from a local table. In the case of a SELECT statement, you can execute a statement affected by this rule if none of the remaining rules require the statement to be remote-mapped. However, you might be able to execute the SQL statement if the unsupported operator or construct can be executed through a callback link. In the case of an INSERT, UPDATE, or DELETE statement, the SQL statement cannot be executed (see Rule B). For example: DELETE FROM WHERE hiredate > :1 This can be resolved by replacing special functions with a bind variable. The previous statement returns the following error message: ORA-02070: database REMOTE_DB does not support special functions in this context For a non-Oracle database for which callbacks are not supported, this can (by default) result in a restriction error.įor example, consider the following statement: DELETE FROM WHERE hiredate > sysdate A remote-mapped statement with these functions contains a callback link.
These functions must be executed at the originating site. INSERT INTO (empno, ename, deptno) VALUES (Īnother special case involves session-specific SQL functions such as USER, USERENV, and SYSDATE.
For example: DECLAREĬURSOR remote_insert IS SELECT * FROM emp The workaround is to write a PL/SQL block. If callback links are not supported by a particular gateway, the previous INSERT statements returns the following error: ORA-02025: all tables in the SQL statement must be at the remote database For more information, see your database gateway documentation to determine if callback links work with the database gateway that you are using. Even though callback links are supported in generic Heterogeneous Services, they may not be implemented in all Heterogeneous Services agents.
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