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  1. Core Server
  2. SERVER-12055

Use better bounds (like undefined) when matching empty array

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    • Type: Icon: Bug Bug
    • Resolution: Duplicate
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: Querying
    • None
    • Fully Compatible
    • ALL

      When searching for an empty array if we match on "undefined" in the index we can use the index to find them. Also, searching for $size:0 could also be re-written to the empty array, and use the same bounds.

      Currently searching for an empty array with an index on the array does this:

      // 2.4.x
find({a:[]}).explain()
{
	"cursor" : "BtreeCursor a_1 multi",
	"isMultiKey" : false,
	"n" : 1,
	"nscannedObjects" : 1,
	"nscanned" : 1,
	"nscannedObjectsAllPlans" : 1,
	"nscannedAllPlans" : 1,
	"scanAndOrder" : false,
	"indexOnly" : false,
	"nYields" : 0,
	"nChunkSkips" : 0,
	"millis" : 0,
	"indexBounds" : {
		"a" : [
			[ null, null ],
			[ [], [] ]
		]}}

// 2.5.5--pre (12/11/13)
{
	"cursor" : "BtreeCursor a_1",
	"isMultiKey" : false,
	"n" : 1,
	"nscannedObjects" : 2,
	"nscanned" : 2,
	"nscannedObjectsAllPlans" : 4,
	"nscannedAllPlans" : 4,
	"scanAndOrder" : false,
	"indexOnly" : false,
	"nYields" : 1,
	"nChunkSkips" : 0,
	"millis" : 2,
	"indexBounds" : {
		"a" : [[{
					"$minElement" : 1
				},
				{
					"$maxElement" : 1
				}]]}}

            Assignee:
            david.storch@mongodb.com David Storch
            Reporter:
            scotthernandez Scott Hernandez (Inactive)
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              Created:
              Updated:
              Resolved: