System and method for segmented evaluation of database queries

A method of providing information from a database comprising the acts of:

• determining that a relational expression includes:
• a first join operator having:
• a first operand which includes a first instance of a first relation based on information stored in said database, said first relation having a set of rows and a set of columns;
• a second operand including a second instance of said first relation;
• and
• a first predicate which is, or conjunctively includes, an equality comparison between one or more columns of said first instance of said first relation and corresponding one or more columns of said second instance of said first relation;
• and
• a second join operator having:
• a third operand which includes the result of said first join operator;
• a fourth operand including a second relation based on information stored in said database;
• and
• a second predicate;
• performing a join of said second relation and said first relation using said second predicate to produce an intermediate result;
• segmenting said intermediate result based on said one or more columns to produce one or more segments of said intermediate result;
• and
• applying said first join operator including said first predicate separately to each of said segments.

A method of providing information from a database comprising the acts of:

• determining that a first relational expression includes a join operator having:
• a first operand which includes a first relation based on information stored in said database;
• a second operand which includes an operator calling for a relational fragment to be applied successively to segments of said second relation, said second relation being based on information stored in said database, said segments of said second relation being based on distinct values of one or more columns of said second relation;
• and
• a predicate;
• creating a second relational expression that includes:
• an operator calling for said relational fragment to be applied successively to segments of a third relation, said segments of said third relation being based on distinct values of said one or more columns and all columns of said first relation, said third relation being the result of a join operator having:
• a third operand which includes said first relation;
• a fourth operand which includes said second relation;
• and
• said predicate;
• and
• evaluating said second relational expression.