Executing a query expression via a database system by processing a prior row index identifier

A query and response sub-system of a database system, wherein the query and response sub-system comprises:

• a plurality of computing device clusters, wherein a computing device cluster of the plurality of computing device clusters includes a plurality of computing devices, wherein a computing device of the plurality of computing devices includes a plurality of computing nodes, wherein a first computing node of the plurality of computing nodes is operable to:
• receive a query, wherein the query includes a plurality of sets of code terms, wherein a set of code terms of the plurality of sets of code terms includes a call to a computing window function, the call including:
• a computing window function keyword identifying the computing window function in accordance with a computing window function definition;
• a window definition identifying an ordered set of rows of a dataset stored in a store and compute sub-system, wherein the dataset includes a plurality of rows of columnar data, and wherein the columnar data includes a plurality of columns of data;
• and
• an argument indicating a basis upon which output for the ordered set of rows is generated, wherein the argument includes a column reference that includes a prior row index identifier identifying a column value of a previous row relative to a given row of the ordered set of rows;
• and
• execute the computing window function in accordance with execution of the query by:
• accessing the ordered set of rows of the dataset identified by the window definition;
• generating an output column for the ordered set of rows by evaluating the argument of the computing window function for rows of the ordered set of rows, wherein generating the output column includes performing an operation upon the column value of the previous row relative to the given row as identified by the prior row index identifier of the column reference;
• and
• appending the output column to the ordered set of rows as part of a query resultant of the query;
• and
• communicate the query resultant for the query.

A computer readable memory device that comprises:

• a memory that stores operational instructions that, when executed by a first computing node of a plurality of computing nodes of plurality of computing devices of a computing device cluster of a plurality of computing device clusters, cause the first computing node to:
• receive a query, wherein the query includes a plurality of sets of code terms, wherein a set of code terms of the plurality of sets of code terms includes a call to a computing window function, the call including:
• a computing window function keyword identifying the computing window function in accordance with a computing window function definition;
• a window definition identifying an ordered set of rows of a dataset stored in a store and compute sub-system, wherein the dataset includes a plurality of rows of columnar data, and wherein the columnar data includes a plurality of columns of data;
• and
• an argument indicating a basis upon which output for the ordered set of rows is generated, wherein the argument includes a column reference that includes a prior row index identifier identifying a column value of a previous row relative to a given row of the ordered set of rows;
• and
• execute the computing window function in accordance with execution of the query by:
• accessing the ordered set of rows of the dataset identified by the window definition;
• generating an output column for the ordered set of rows by evaluating the argument of the computing window function for rows of the ordered set of rows, wherein generating the output column includes performing an operation upon the column value of the previous row relative to the given row as identified by the prior row index identifier of the column reference;
• and
• appending the output column to the ordered set of rows as part of a query resultant of the query;
• and
• communicate the query resultant for the query.