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  1. Core Server
  2. SERVER-17148

Remove plans do not need a FETCH stage

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    • Type: Icon: Improvement Improvement
    • Resolution: Unresolved
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: Querying
    • None
    • Query Optimization
    • Quint 9 09/18/15, QO 2024-02-19

      Currently, indexed .remove() plans will always fetch the documents associated with the index keys before performing the remove:

      > t.drop()
true
> t.ensureIndex({x: 1})
{
	"createdCollectionAutomatically" : true,
	"numIndexesBefore" : 1,
	"numIndexesAfter" : 2,
	"ok" : 1
}
> t.explain().remove({x: {$gte: 5, $lte: 10}})
{
	"queryPlanner" : {
		"plannerVersion" : 1,
		"namespace" : "test.t",
		"indexFilterSet" : false,
		"parsedQuery" : {
			"$and" : [
				{
					"x" : {
						"$lte" : 10
					}
				},
				{
					"x" : {
						"$gte" : 5
					}
				}
			]
		},
		"winningPlan" : {
			"stage" : "DELETE",
			"inputStage" : {
				"stage" : "FETCH", // This stage is not needed!
				"inputStage" : {
					"stage" : "IXSCAN",
					"keyPattern" : {
						"x" : 1
					},
					"indexName" : "x_1",
					"isMultiKey" : false,
					"direction" : "forward",
					"indexBounds" : {
						"x" : [
							"[5.0, 10.0]"
						]
					}
				}
			}
		},
		"rejectedPlans" : [ ]
	},
	"serverInfo" : {
		"host" : "dstorch-desktop",
		"port" : 27017,
		"version" : "3.1.0-pre-",
		"gitVersion" : "ee4db2a36eb894e2694fea781ab70f0cca33d0b8"
	},
	"ok" : 1
}

      As an optimization, we could change the query planner to generate indexed .remove() plans without the FETCH stage.

            Assignee:
            backlog-query-optimization [DO NOT USE] Backlog - Query Optimization
            Reporter:
            david.storch@mongodb.com David Storch
            Votes:
            5 Vote for this issue
            Watchers:
            35 Start watching this issue

              Created:
              Updated: