MarkLogic interview: What is E-node and D-node in the MarkLogic?

 

Q.1. What is E-node and D-node in the MarkLogic?

Ans: Evaluator node (e-node):  E-node that evaluate xquery programs, XCC/XDBC request, and other server request also. E-node also talk with D-node if needs forest data otherwise e-node request evaluated entirely on the e-node.

Example-1: Suppose you run query to do some mathematical calculation and you have no need of forest data, in this case query run entirely on E-Node. Query will not talk with D-node in this case.    

Example-2: Suppose you want extract some forest data, in this case you will run a query on E-node and E-node send a request to D-node for fetching data. D-Node fetch the data and return to E-node. 

Data node (D-node): 

D-nodes are responsible for maintaining transaction integrity during insert, update and delete operations.  Or we can say D-node is responsible for only data.

Example: if you want to import data without using of E-node, in this case you use to MLCP for this.

MLCP work directly on D-node to import or export data. 

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