Aggregation over high-cardinality dimensions using uniqueness indices

A method comprising:

• receiving a query specifying a database table, an aggregate function, a plurality of grouping columns and an aggregation column;
• determining a uniqueness index associated with each of the plurality of grouping columns, where each row of each uniqueness index corresponds to a row of the grouping column associated with the uniqueness index and indicates whether the value in the row of the associated grouping column is unique or not unique within the associated grouping column;
• determining whether a tuple of a first row of the grouping columns in the database tables is unique in the grouping columns based on the determined uniqueness indices;
• if it is determined that the tuple of the first row of the grouping columns is unique in the grouping columns, storing a result set entry including the tuple and an aggregation value determined based on a value of the aggregation column in the first row;
• and
• if it is determined that the tuple of the first row of the grouping columns is not unique in the grouping columns, determining a key based on the tuple and perform a hash lookup using the key.

A non-transitory medium storing processor-executable program code, the program code executable by a computing system to cause the computing system to:

• receive a query specifying a database table, an aggregate function, one or more grouping columns and an aggregation column;
• determine a uniqueness index associated with each of the one or more grouping columns, where each row of each uniqueness index corresponds to a row of the grouping column associated with the uniqueness index and indicates whether the value in the row of the associated grouping column is unique or not unique within the associated grouping column;
• determine whether a tuple of a first row of the one or more grouping columns in the database tables is unique in the one or more grouping columns based on the uniqueness indices;
• if it is determined that the tuple of the first row of the grouping columns is unique in the one or more grouping columns, store a result set entry including the tuple and an aggregation value determined based on a value of the aggregation column in the first row;
• and
• if it is determined that the tuple of the first row of the one or more grouping columns is not unique in the one or more grouping columns, determine a key based on the tuple and perform a hash lookup using the key.