23. The method of claim 17 , wherein: said rule is a first rule, said left-side expression is a first left-side expression, said right-side expression is a first right-side expression, and said window function is a first window function; said model clause further comprises a second rule, wherein said second rule comprises a second left-side expression and a second right-side expression, wherein said second right-side expression includes a second window function; said first window function specifies first one or more partition columns by which to partition a second set of rows in said relation into partitions, wherein said second set of rows includes first one or more cells that are identified by said first left-side expression of said first rule; said second window function specifies second one or more partition columns by which to partition a third set of rows into partitions, wherein said third set of rows includes second one or more cells that are identified by said second left-side expression of said second rule; and said step of said database server executing said query comprises: based on said first left-side expression, determining said second set of rows in said relation; based on said first one or more partition columns, partitioning said second set of rows into first one or more subsets of rows; based on said second left-side expression, determining said third set of rows in said relation; based on said second one or more partition columns, partitioning said third set of rows into second one or more subsets of rows; said step of producing said first set of rows comprises producing said first set of rows based on at least one of said first one or more subsets of rows; producing a fourth set of rows based on at least one of said second one or more subsets of rows; and evaluating said second window function based on said fourth set of rows.
23. The method of claim 17 , wherein: said rule is a first rule, said left-side expression is a first left-side expression, said right-side expression is a first right-side expression, and said window function is a first window function; said model clause further comprises a second rule, wherein said second rule comprises a second left-side expression and a second right-side expression, wherein said second right-side expression includes a second window function; said first window function specifies first one or more partition columns by which to partition a second set of rows in said relation into partitions, wherein said second set of rows includes first one or more cells that are identified by said first left-side expression of said first rule; said second window function specifies second one or more partition columns by which to partition a third set of rows into partitions, wherein said third set of rows includes second one or more cells that are identified by said second left-side expression of said second rule; and said step of said database server executing said query comprises: based on said first left-side expression, determining said second set of rows in said relation; based on said first one or more partition columns, partitioning said second set of rows into first one or more subsets of rows; based on said second left-side expression, determining said third set of rows in said relation; based on said second one or more partition columns, partitioning said third set of rows into second one or more subsets of rows; said step of producing said first set of rows comprises producing said first set of rows based on at least one of said first one or more subsets of rows; producing a fourth set of rows based on at least one of said second one or more subsets of rows; and evaluating said second window function based on said fourth set of rows. 24. The method of claim 23 , wherein said first one or more partition columns are the same as said second one or more partition columns.