Liya Fan created CALCITE-3827: --------------------------------- Summary: Reduce the time complexity of finding in-edges of a vertex in the graph Key: CALCITE-3827 URL: https://issues.apache.org/jira/browse/CALCITE-3827 Project: Calcite Issue Type: Improvement Components: core Reporter: Liya Fan
In the current graph implementation, it takes O(1) time to find the out-edges of a vertex, but O(e) time (where e is the total number of edges in the graph) to find the in-edges of a vertex. In some scenarios (e.g. clearing cache in hep planner), this may have severe performance penalty. To solve this problem, we add a inward edge table, in addition to the existing outward edge table, to the graph. This helps to reduce the time complexity for finding in-edges to O(1). Please note that, there is extra performance overhead for maintaining the in edge table, when adding/deleting vertices to the graph. However, the added overhead only takes O(1) time. Finally, it should be noted that, some existing operations can benefit from this improvement (topological sort). -- This message was sent by Atlassian Jira (v8.3.4#803005)