15. The apparatus according to claim 12 , wherein the instructions further cause the processor to be configured to: set a quantity of graph nodes in the reduction subgraph to 0; set a quantity of query nodes and a quantity of graph nodes matching the query nodes to 0, wherein a query node and a graph node matching the query node are stored in storage space; set a dynamic reduction parameter to a first preset value; store a start query node in the query topology structure and the start graph node into the storage space; read the query node and the graph node matching the query node stored in the storage space; determine whether the reduction subgraph comprises the read graph node; add the read graph node to the reduction subgraph when the reduction subgraph does not comprise the read graph node; determine that the resource occupied by the reduction subgraph does not exceed the preset available resource condition; calculate an access cost of a to-be-queried graph node adjacent to the read graph node, and filter out the second to-be-queried graph node whose access cost exceeds the preset first access cost and the association relationship comprising the second to-be-queried graph node whose access cost exceeds the first access cost, according to the query topology relationship between the query nodes in the query topology structure; output, according to the dynamic reduction parameter, an access sequence that is to be stored into the storage space; determine whether the storage space is empty; continue to read the query node and the graph node matching the query node stored in the storage space, until the quantity of query nodes and the quantity of graph nodes matching the query nodes are 0 when the storage space is not empty, wherein the query node and the graph node matching the query node are stored in the storage space; determine whether the reduction subgraph changes when the storage space is empty; and end the filter out process in order to obtain the reduction subgraph when the reduction subgraph does not change, wherein the start graph node matches the start query node, wherein the read graph node comprises the start graph node or the to-be-queried graph node, wherein an access cost of a to-be-queried graph node in the access sequence does not exceed the first access cost, and wherein the dynamic reduction parameter controls a quantity of to-be-queried graph nodes in the access sequence.
12. The apparatus according to claim 11 , wherein instructions further cause the processor to be configured to: generate a query topology structure according to the query condition; and filter out, according to a query topology relationship between query nodes in the query topology structure, a preset first access cost of accessing the first to-be-queried graph node, and the preset available resource condition, the second to-be-queried graph node in the graph data set whose access cost exceeds the preset first access cost and the association relationship in the graph data set comprising the second to-be-queried graph node in order to obtain the reduction subgraph, wherein the query topology structure comprises a plurality of query nodes and the query topology relationship between each query node and another query node in the plurality of query nodes, and wherein a resource occupied by the reduction subgraph does not exceed the preset available resource condition.