System, method, and program for object building in queries over object views

A method performed by a computer program on a computer usable medium, the method comprising:

• receiving view definitions;
• and
• generating object-oriented class definitions from the view definitions, wherein a view collection v is of the view type V and has an implementation M for V specified as a SELECT statement, and wherein the step of generating produces the class definitions according to the following rules:
• a) ordering elements in an object language class constructor as an ordering of elements in a FROM clause of M;
• b) passing, as an argument to an object constructor, a handle on a binding of an ith element, if the ith element in the FROM clause is a view type;
• and
• c) passing, as another argument to the object constructor, a row type if the jth element in the FROM clause of M is a relational table and ordering arguments of the row type as an order to columns present in the row type.

A method performed by a query engine in a data processing system, the method comprising:

• receiving from an application having an object-oriented language, a query referencing a view type;
• generating application objects in memory, at run-time, from the view type;
• and
• returning handles on the application objects to the application, wherein given a view collection v of view type V and an associated implementation M for V specified as a SELECT statement, the view type application objects of type V are generated for a query over v according to the following rules:
• a) If V is a view type, an object building procedure call used to build V has arguments whose ordering is that of elements in the FROM clause of M, and if the ith element in the FROM clause is a view type, then a handle on the binding to the ith element is passed as argument to the object building procedure call;
• and
• b) If V is a view type and the jth element in the FROM clause of M is a relational table, the object building procedure call used to create V has as its jth element a row type that is passed as argument to the call, wherein the row type is a generic type that is built based upon a schema of the row type, and the order of arguments is given by the order of columns present in the row type.

A method implemented in a query processing system, the method comprising:

• receiving, from an application, a query referencing a view type;
• generating a query plan having an object building procedure call having arguments whose ordering is that of elements in a FROM clause of the query;
• passing, as an argument to the object building procedure call, a handle on a binding to an ith element if the ith element in the FROM clause is a view type;
• and
• passing, as a jth argument to the object building procedure call, a row type based upon a schema of a database row, if the jth element in the FROM clause is a relational table.

A query engine comprising:

• means for receiving, from an application, a query referencing a view type;
• means for generating a query plan having an object building procedure call having arguments whose ordering is that of elements in a FROM clause of the query;
• means for passing, as an argument to the object building procedure call, a handle on a binding to an ith element if the ith element in the FROM clause is a view type;
• and
• means for passing, as a jth argument to the object building procedure call, a row type based upon a schema of a database row, if the jth element in the FROM clause is a relational table.

A query system comprising:

• means for receiving from an application having an object-oriented language, a query referencing a view type;
• means for generating application objects in memory, at run-time, from the view type;
• and
• means for returning handles on the application objects to the application, wherein given a view collection v of view type V and an associated implementation M for V specified as a SELECT statement, the means for generating produces the view type application objects of type V for the query over v according to the following rules:
• a) If V is a view type, an object building procedure call used to build V has arguments whose ordering is that of elements in the FROM clause of M, and if the ith element in the FROM clause is a view type, then a handle on the binding to the ith element is passed as argument to the object building procedure call;
• and
• b) If V is a view type and the jth element in the FROM clause of M is a relational table, the object building procedure call used to create V has as its jth element a row type that is passed as argument to the call, wherein the row type is a generic type that is built based upon a schema of the row type, and the order of arguments is given by the order of columns present in the row type.

A program on a computer usable medium for processing queries, the program comprising:

• means for receiving, from an application, a query referencing a view type;
• means for generating a query plan having an object building procedure call having arguments whose ordering is that of elements in a FROM clause of the query;
• means for passing, as an argument to the object building procedure call, a handle on a binding to an ith element if the ith element in the FROM clause is a view type;
• and
• means for passing, as a jth argument to the object building procedure call, a row type based upon a schema of a database row, if the jth element in the FROM clause is a relational table.