3.2.3.1.1 About Creating R Proxy Objects for Database Objects
To create proxy objects that enable accessing and manipulating database tables and views, you use the ore.sync function.
When you invoke ore.connect in an R session, Oracle Machine Learning for R creates a connection to a schema in an Oracle Database instance. The ore.sync function creates an ore.frame object that is a proxy for a table in a schema. You can use the ore.attach function to add an R environment that represents a schema in the R search path.
When you use the ore.sync function to create an ore.frame object as a proxy for a database table, the name of the ore.frame proxy object is the same as the name of the database object. Each ore.frame proxy object contains metadata about the corresponding database object.
You can use the proxy ore.frame object to select data from the table. When you execute an R operation that selects data from the table, the operation returns the current data from the database object. However, if some application has added a column to the table, or has otherwise changed the metadata of the database object, the ore.frame proxy object does not reflect such a change until you again invoke ore.sync for the database object.
If you invoke the ore.sync function with no tables specified, and if the value of the all argument was FALSE in the ore.connect function call that established the connection to the Oracle database instance, then the ore.sync function creates a proxy object for each table in the schema specified by ore.connect. You can use the table argument to specify the tables for which you want to create ore.frame proxy objects.
Tip:
To conserve memory resources and save time, you should only add proxies for the tables that you want to use in your R session.
With the schema argument, you can specify the schema for which you want to create an R environment and proxy objects. Only one environment for a given database schema can exist at a time. With the use.keys argument, you can specify whether you want to use primary keys in the table to order the ore.frame object.
Tip:
Ordering, or requiring a sort on data to ensure order, can be expensive in general and should be avoided unless needed. Because most operations in R do not need ordering, you should generally set use.keys to FALSE unless you need ordering for sampling data or some other purpose.
With the query argument, you can specify a SQL SELECT statement. This enables you to create an ore.frame for a query without creating a view in the database. This can be useful when you do not have the CREATE VIEW system privilege for the current schema. You cannot use the schema argument and the query argument in the same ore.sync invocation.
You can use the ore.ls function to list the ore.frame proxy objects that correspond to database tables in the environment for a schema. You can use the ore.exists function to find out if an ore.frame proxy object for a database table exists in an R environment. The function returns TRUE if the proxy object exists or FALSE if it does not. You can remove an ore.frame proxy object from an R environment with the ore.rm function.
Parent topic: Using Proxy Objects for Database Data