US 5,787,431 AGranted

Database development system with methods for java-string reference lookups of column names

AssigneeBorland International, Inc.

InventorSteven T. Shaughnessy

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Abstract

A Java-based rapid application development (RAD) environment for creating applications providing named-based programmatic access to information from columns in databases is described. For increasing the efficiency by which named-based references to database columns are processed by application programs, the system provides methodology for rapid lookups of column names, using a reference cache storing 32-bit references to immutable strings (e.g., Java strings). The reference cache is preferably constructed as a least-recently allocated cache, thereby allowing allocation to occur in a round-robin fashion, with the oldest item allocated being the first item bumped from cache when the cache overflows. Each cache entry stores a reference (e.g., four-byte pointer or handle to a string) and an ordinal entry (i.e. the corresponding database ordinal). As a reference to a particular database column occurs during execution of a program, the reference cache fills with a reference to that column name as well as the corresponding column ordinal. Accordingly, program execution proceeds with comparison of existing items in the cache, using a sequence of rapid, in-line comparisons involving simple data types (e.g., 32-bit references for the column name string). This approach minimizes the need to perform hash lookups or string comparison operations.

Claims20

Dependent claims

In a development system for creating a program which includes programmatic access to columns of database tables, an improved method for determining an ordinal representing an offset within a database table of a column which has been referenced within a program by name, the method comprising:

allocating memory for storing a plurality of reference cache entries, each cache entry storing a reference to a text string representing a name for a given column and further storing an ordinal for the given column;
upon a request for an ordinal of a particular column, said request including the text string which represents the name for the particular column,
(i) attempting to determine the ordinal by examining the reference cache for an entry storing a reference which matches a corresponding reference to a text string representing the name for the particular column;
(ii) if the reference cache has no such entry,
(1) determining the ordinal based, at least in part, on comparison of the text string representing the name for the particular column, and
(2) updating the reference cache by storing a cache entry having a reference to the text string and the ordinal for the particular column, so that subsequent requests for the ordinal of the particular column can be satisfied based on examination of the reference cache;
and
(iii) providing the determined ordinal for the particular column, so that the program has programmatic access to information stored at the particular column.

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Dependencies are inferred from the claim text.