Reduced memory row hash match scan join for a partitioned database system

A database system for iteratively selecting rows from a first table, the database system including a second table, the first table including rows and columns and being divided by rows into partitions and at least one of the partitions in the table being populated by one or more rows, the system comprising:

• one or more nodes;
• a plurality of CPUs, each of the one or more nodes providing access to one or more CPUs;
• a plurality of processes, each of the one or more CPUs providing access to one or more virtual processes;
• each process configured to manage data, including the partitioned database table, stored in one of a plurality of data-storage facilities;
• a partitioned table access component configured to select rows from at least the first table by
• a. defining a subset of the populated partitions of the first table that excludes at least one populated partition of the first table;
• b. creating a file context, which stores at least location data for a row and a first value associated with the row, for each populated partition in the subset of the populated partitions of the first table;
• c. determining the lowest first value stored by the file contexts for the first table;
• d. identifying rows with a particular first value by at least reading the file contexts of the first table;
• and
• e. repeating a through d until the subsets of the populated partitions of the first table have included all the populated partitions of the first table.

A computer program, stored in a tangible medium, for selecting rows from a first table, the first table having rows and columns and divided by row into partitions, at least one of the partitions being populated by rows, the program comprising executable instructions that cause a computer to:

• a. define a subset of the populated partitions of the first table that excludes at least one populated partition of the first table;
• b. create a file context, which stores at least location data for a row and a first value associated with the row, for each populated partition in the subset of the populated partitions of the first table;
• c. determine the lowest first value stored by the file contexts for the first table;
• d. identify rows with a particular first value by at least reading the file contexts of the first table;
• and
• e. repeat a through d until the subsets of the populated partitions of the first table have included all the populated partitions of the first table.