Compaq Computer Corporation, Inc.

Peter N Lohman

Robert Matthew Wehrmeister

Mark E Melton

A database query compiler and compilation method has special facilities for compiling a query that includes one or more of a predefined set of running and moving sequence functions. The compiler converts the query into a predefined normalized form suitable for compilation using a running and moving function normalizer. The running and moving function normalizer converts each running and moving sequence function in the set into a corresponding ordered set of one or more executable statements, which include at least one Offset sequence function that accesses data in an auxiliary field of a row of a table. An offset sequence function compiler, compiles each Offset sequence function, Offset(argument, index), in the normalized database query into a compiled set of instructions, including instructions for storing and reading the auxiliary fields to and from a buffer that is separate from the table. The buffer is preferably stored in volatile, main memory. As a result, when the Offset sequence function is executed, information from a previous is accessed without having to change the cursor position for the table.

System and method for computing running and moving sequence functions in a database system

A database query compiler and compilation method has special facilities for compiling a query that includes an Offset sequence function, Offset(argument, index). During execution of the query, while the cursor for a table is pointing to a current row, the Offset function is used to access information from a previously accessed row. The argument of the Offset sequence function is a specified function of information associated with the previously accessed row of the table. The previously accessed row has a position that is index rows before the current row referenced by the cursor for the table. During compilation, the argument of the Offset sequence function is parsed to determine a set of auxiliary fields for each row of the table. Each auxiliary field of a row contains information that may be accessed during execution of the Offset sequence function while the cursor for that table is pointing to a subsequent row. The Offset sequence function is converted into a compiled set of instructions, including instructions for storing and reading the auxiliary fields to and from a buffer that is separate from the table. The buffer is preferably stored in volatile, main memory. As a result, the Offset sequence function is executed, and information from a previous row is accessed, without having to change the cursor position for the table.

System and method for computing an offset sequence function in a database system

A database query compiler and compilation method has special facilities for compiling a query that includes a Rows Since sequence function, Rows Since (search condition). A query normalizer includes a Rows Since function normalizer for normalizing the Rows Since sequence function. The Rows Since function normalizer parses the search condition of the Rows Since function to identify each reference to information from a previously access row and converts each such identified reference into an Offset sequence function, Offset(argument, index). The argument of the Offset sequence function is a specified function of the identified information from a previously accessed row of the table. The previously accessed row has a position that is index rows before the current row referenced by the cursor for the table. The query compiler places the resulting normalized search condition in a search loop that traverses successively earlier rows in the table until it finds a row that satisfies the search condition. An offset sequence function compiler, compiles each Offset sequence function, Offset(argument, index), in the normalized database query into a compiled set of instructions, including instructions for storing and reading the auxiliary fields to and from a buffer that is separate from the table. The buffer is preferably stored in volatile, main memory. As a result, when the Offset sequence function is executed, information from a previous is accessed without having to change the cursor position for the table.

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Peter N Lohman