Check whether an dbObjectId handle object is valid or not
Support function that verifies that an dbObjectId holding a reference to a foreign object is still valid for communicating with the RDBMS
dbObjectId are R/S-Plus remote references to foreign (C code) objects.
This introduces differences to the object's semantics such as
persistence (e.g., connections may be closed unexpectedly),
thus this function provides a minimal verification to ensure
that the foreign object being referenced can be contacted.
- a logical scalar.
cursor <- dbSendQuery(con, sql.statement) isIdCurrent(cursor)