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This is an extended version of the Pruning Var Expand algorithm, improving performance on paths with a max length of 5 or more, on randomized graphs. The Full Pruning Var Expand (FullPrune) manages to prune paths below the min-length by storing emit-state for all touched nodes, apart from the full expand depths. This also makes the algorithm fully distinct, so no additional distinct operator is needed afterwards.
systay
reviewed
Mar 21, 2017
| assert(min <= max) | ||
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| /* | ||
| This algorithm has been implemented using a state machine. This Cypher statement shows the static connections between the states. |
systay
reviewed
Mar 21, 2017
| * @return the full expand depth | ||
| */ | ||
| def minOutgoingDepth(incomingRelId: Long): Int = { | ||
| var max = Constants.VERY_BIG_VALUE |
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How about using Integer.MAX_VALUE instead of this arbitrarily chosen VERY_BIG_VALUE?
This is the only place VERY_BIG_VALUE is used, so if that is changed, we no longer need to declare that constant - making the code easier to read (because a reader no longer needs to try to understand why the value is what it is).
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New Cypher operator for improved handling of longer var-length expands with distinct start node / end node combinations. This new operator is called FullPruningVarExpand, and is planned for var-lengths above
4..5. Above this length the FullPruningVarExpand gives improved execution times in most cases, with speed-ups of an order of magnitude or more on even longer var-lengths.changelog: Improved cypher execution speed on variable length queries where only the distinct pairs of start and end node are of interest. One query to benefit would be
MATCH (a)-[*4..5]->(b) RETURN DISTINCT a, b.