/ /

$setIsSubset（式演算子）

定義

$setIsSubset

2 つの配列を受け取り、最初の配列が 2 番目の配列のサブセットである場合はtrueを返し、最初の配列が 2 番目の配列と等しい場合を返し、それ以外の場合はfalseを返します。

$setIsSubset の構文は次のとおりです。

{ $setIsSubset: [ <expression1>, <expression2> ] }

引数は、それぞれが配列に変換される限り、どのような有効な式でも使用できます。式の詳細については、「式」を参照してください。

動作

$setIsSubset performs set operation on arrays, treating arrays as sets. If an array contains duplicate entries, $setIsSubset ignores the duplicate entries. $setIsSubset ignores the order of the elements.

If a set contains a nested array element, $setIsSubset does not descend into the nested array but evaluates the array at top-level.

例

結果

{ $setIsSubset: [ [ "a", "b", "a" ], [ "b", "a" ] ] }

true

{ $setIsSubset: [ [ "a", "b" ], [ [ "a", "b" ] ] ] }

false

例

以下のドキュメントを持つflowersコレクションを検討してください。

db.flowers.insertMany( [
   { "_id" : 1, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid" ] },
   { "_id" : 2, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "orchid", "rose", "orchid" ] },
   { "_id" : 3, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid", "jasmine" ] },
   { "_id" : 4, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "jasmine", "rose" ] },
   { "_id" : 5, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ ] },
   { "_id" : 6, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose" ], [ "orchid" ] ] },
   { "_id" : 7, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose", "orchid" ] ] },
   { "_id" : 8, "flowerFieldA" : [ ], "flowerFieldB" : [ ] },
   { "_id" : 9, "flowerFieldA" : [ ], "flowerFieldB" : [ "rose" ] }
] )

The following operation uses the $setIsSubset operator to determine if the flowerFieldA array is a subset of the flowerFieldB array:

db.flowers.aggregate(
   [
     { $project: { flowerFieldA:1, flowerFieldB: 1, AisSubset: { $setIsSubset: [ "$flowerFieldA", "$flowerFieldB" ] }, _id:0 } }
   ]
)

この操作は次の結果を返します。

{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid" ], "AisSubset" : true }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "orchid", "rose", "orchid" ], "AisSubset" : true }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid", "jasmine" ], "AisSubset" : true }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "jasmine", "rose" ], "AisSubset" : false }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ ], "AisSubset" : false }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose" ], [ "orchid" ] ], "AisSubset" : false }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose", "orchid" ] ], "AisSubset" : false }
{ "flowerFieldA" : [ ], "flowerFieldB" : [ ], "AisSubset" : true }
{ "flowerFieldA" : [ ], "flowerFieldB" : [ "rose" ], "AisSubset" : true }

戻る

$setIntersection

$setUnion