Row hash match scan join using summary contexts for a partitioned database system

A database system for selecting rows from a partitioned database table, the partitioned database table including rows and columns and being divide 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 the table by:
• a. creating a plurality of partition contexts, each partition context corresponding to a populated partition and storing at least a first value associated with a row;
• b. determining the lowest first value stored by the partition contexts;
• and
• c. identifying rows with a particular first value including:
• i reading the partition contexts;
• ii. creating a temporary file context corresponding to one of the partition contexts, the temporary file context including location data for a data block of rows in memory;
• and
• iii. reading rows from the data block rows in memory.

A computer program, stored in a tangible medium, for selecting rows from a partitioned database table, the program comprising executable instructions that cause a computer to:

• a. create a plurality of partition contexts, each partition context t corresponding to a populated partition and storing at least a first value associated with a row;
• b. determine the lowest first value stored by the partition contexts;
• and
• c. identify rows with a particular first value by:
• i. reading the partition contexts;
• ii. creating a temporary file context corresponding to one of the partition contexts, the temporary file context including location data for a data block of rows in memory;
• and
• iii. reading rows from the data block rows in memory.