| CPC G06F 16/27 (2019.01) [G06F 9/466 (2013.01); G06F 16/9024 (2019.01)] | 20 Claims |

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1. A compute node comprising:
a processor;
a memory device that stores program code structured to cause the processor to:
receive, from a distributed query processor, a first query task and a hierarchical nested identifier, the hierarchical nested identifier including at least a statement-level identifier associated with a statement-level transaction, a vertex-level identifier associated with a vertex of a directed acyclic graph, and a task-level identifier associated with the first query task in the directed acyclic graph, the vertex-level identifier nested between the statement-level identifier and the task-level identifier;
determine a first visible version of data in a queried database according to data visibility rules based at least on the transaction-level identifier, the vertex-level identifier, and the task-level identifier; and
execute the first query task on the first visible version of data.
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