Method and apparatus for incremental refresh of summary tables in a database system

A computer-readable medium carrying one or more sequences of instructions for performing incremental refresh of a summary table that has a plurality of base tables, wherein execution of the one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of:

• assigning a hypothetical load sequence to said plurality of base tables;
• generating delta summary data by performing the following steps for at least one of the base tables:
• performing a join between newly loaded data for said base table, a pre-load state of a first set of tables, and post-load state of a second set of tables;
• wherein said first set of tables are those tables of said plurality of base tables that are after said base table in said hypothetical load sequence;
• wherein said second set of tables are those tables of said plurality of base tables that are before the base table in said hypothetical load sequence;
• and
• merging said delta summary data into said summary table.

A method for refreshing a summary table that is derived from a plurality of base tables, the method comprising the steps of:

• loading new data into one or more base tables of said plurality of base tables between a first point in time and a second point in time, wherein summary values in said summary table initially reflect the state of said plurality of base tables at said first point in time;
• assigning a sequence to said plurality of base tables;
• for at least one of said plurality of base tables, performing the steps of generating an individual delta summary based on
• (a) new data loaded into said base table between said first point in time and said second point in time;
• (b) data that existed in a first set of said plurality of base tables at said first point in time, said first set including all tables of said plurality of base tables that are after said base table in said sequence;
• and
• (c) data that existed in a second set of said plurality of base tables at said second point in time, said second set including all tables of said plurality of base tables that are before said base table in said sequence;
• and
• merging said individual delta summary into said summary table.

A system comprising:

• one or more memory devices that have stored therein a plurality of base tables;
• a summary table that is derived from said plurality of base tables;
• sequences of instructions for incrementally updating said summary table after new data has been loaded into one or more of said plurality of base tables;
• one or more processors operatively coupled to said one or more memory devices, the one or more processors configured to perform the following steps in response to executing said sequences of instructions:
• assigning a hypothetical load sequence to said plurality of base tables;
• generating delta summary data by performing the following steps for at least one of the base tables
• performing a join between newly loaded data for said base table, a pre-load state of a first set of tables, and a post-load state of a second set of tables;
• wherein said first set of tables are those tables of said plurality of base tables that are after said base table in said hypothetical load sequence;
• wherein said second set of tables are those tables of said plurality of base tables that are before the base table in said hypothetical load sequence;
• and
• merging said delta summary data into said summary table.