PROCESSING AGGREGATE QUERIES IN A GRAPH DATABASE
The disclosed embodiments provide a system for processing queries of a graph database. During operation, the system executes one or more processes for providing the graph database storing a graph, wherein the graph includes a set of nodes, a set of edges between pairs of nodes in the set of nodes, and a set of predicates. Next, the system obtains, from the query, an aggregation by a first attribute and a grouping by a second attribute. The system then uses the second attribute to generate a set of groupings of records in the graph database. For each grouping in the set of groupings, the system applies the aggregation to the first attribute in a subset of the records in the grouping to generate an aggregation result. Finally, the system uses the aggregation result to provide a response to the query.
1 . A method, comprising:
executing a set of processes for processing queries of a graph database storing a graph, wherein the graph comprises a set of nodes, a set of edges between pairs of nodes in the set of nodes, and a set of predicates; and
when a query of the graph database is received, using one or more of the processes to process the query by:
obtaining, from the query, an aggregation by a first attribute and a grouping by a second attribute;
using the second attribute to generate a set of groupings of records in the graph database;
for each grouping in the set of groupings, applying the aggregation to the first attribute in a subset of the records in the grouping to generate an aggregation result; and
using the aggregation result to provide a response to the query.
2 . The method of claim 1 , further comprising:
expanding the query into a set of base terms comprising the aggregation and the grouping prior to generating the aggregation result.
3 . The method of claim 2 , further comprising:
assigning, to the base terms, a set of positions in an evaluation order for the query; and
evaluating the base terms according to the positions in the evaluation order.
4 . The method of claim 3 , wherein assigning the set of positions in the evaluation order to the base terms comprises:
assigning a first position in the evaluation order to a first subset of the base terms comprising the aggregation; and
assigning a second position that is later than the first position in the evaluation order to a second subset of the base terms comprising a subquery in which the aggregation is nested.
5 . The method of claim 4 , wherein assigning the set of positions in the evaluation order to the base terms further comprises:
assigning a third position that is earlier than the first position to a third subset of the base terms comprising a set of edges to which the aggregation is applied.
6 . The method of claim 4 , wherein evaluating the base terms according to the positions in the evaluation order comprises:
evaluating the first subset of the base terms to obtain the aggregation result; and
providing the aggregation result as input to the second subset of the base terms.
7 . The method of claim 2 , wherein the set of base terms comprises a set of edges.
8 . The method of claim 2 , wherein expanding the query into the set of base terms comprises:
using a schema to transform one or more terms in the query into the set of base terms.
9 . The method of claim 1 , wherein generating the aggregation result comprises:
producing the aggregation result as a subgraph of the graph.
10 . The method of claim 1 , wherein the aggregation is at least one of:
a count;
a sum;
a maximum;
a minimum;
an average; and
a percentile.
11 . The method of claim 1 , wherein the aggregation is at least one of:
a rank; and
a pagination.
12 . An apparatus, comprising:
one or more processors; and
memory storing instructions that, when executed by the one or more processors, cause the apparatus to:
execute a set of processes for processing queries of a graph database storing a graph, wherein the graph comprises a set of nodes, a set of edges between pairs of nodes in the set of nodes, and a set of predicates; and
when a query of the graph database is received, use one or more of the processes to process the query by:
obtaining, from the query, an aggregation by a first attribute and a grouping by a second attribute;
using the second attribute to generate a set of groupings of records in the graph database;
for each grouping in the set of groupings, applying the aggregation to the first attribute in a subset of the records in the grouping to generate an aggregation result; and
using the aggregation result to provide a response to the query.
13 . The apparatus of claim 12 , wherein the memory further stores instructions that, when executed by the one or more processors, cause the apparatus to:
expand the query into a set of base terms comprising the aggregation and the grouping prior to generating the aggregation result.
14 . The apparatus of claim 13 , wherein the memory further stores instructions that, when executed by the one or more processors, cause the apparatus to:
assign, to the base terms, a set of positions in an evaluation order for the query; and
evaluate the base terms according to the positions in the evaluation order.
15 . The apparatus of claim 14 , wherein assigning the set of positions in the evaluation order to the base terms comprises:
assigning a first position in the evaluation order to a first subset of the base terms comprising the aggregation; and
assigning a second position that is later than the first position in the evaluation order to a second subset of the base terms comprising a subquery in which the aggregation is nested.
16 . The apparatus of claim 15 , wherein evaluating the base terms according to the positions in the evaluation order comprises:
evaluating the first subset of the base terms to obtain the aggregation result; and
providing the aggregation result as input to the second subset of the base terms.
17 . The apparatus of claim 13 , wherein expanding the query into the set of base terms comprises:
using a schema to transform one or more terms in the query into the set of base terms.
18 . The apparatus of claim 12 , wherein generating the aggregation result comprises:
producing the aggregation result as a subgraph of the graph.
19 . A system, comprising:
a graph database storing a graph, wherein the graph comprises a set of nodes, a set of edges between pairs of nodes in the set of nodes, and a set of predicates; and
a processing module comprising a non-transitory computer-readable medium comprising instructions that, when executed, cause the system to process a query of the graph database by:
obtaining, from the query, an aggregation by a first attribute and a grouping by a second attribute;
using the second attribute to generate a set of groupings of records in the graph database;
for each grouping in the set of groupings, applying the aggregation to the first attribute in a subset of the records in the grouping to generate an aggregation result; and
using the aggregation result to provide a response to the query.
20 . The system of claim 19 , wherein the non-transitory computer-readable medium of the processing module further comprises instructions that, when executed, cause the system to:
expand the query into a set of base terms comprising the aggregation and the grouping prior to generating the aggregation result;
assign, to the base terms, a set of positions in an evaluation order for the query; and
evaluate the base terms according to the positions in the evaluation order.