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Add first, firstN, last, lastN operators and tests (mongodb#14)
* Add first,firstN,last,lastN operators and tests * Add tests on $first and $last
1 parent 0bedc20 commit a939aa0

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lines changed

‎generator/config/accumulator/first.yaml

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name: expression
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type:
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- expression
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tests:
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-
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name: 'Use in $group Stage'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/first/#use-in--group-stage'
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pipeline:
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-
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$sort:
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item: 1
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date: 1
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-
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$group:
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_id: '$item'
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firstSale:
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$first: '$date'
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-
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name: 'Use in $setWindowFields Stage'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/first/#use-in--setwindowfields-stage'
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pipeline:
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-
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$setWindowFields:
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partitionBy: '$state'
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sortBy:
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orderDate: 1
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output:
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firstOrderTypeForState:
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$first: '$type'
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window:
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documents:
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- 'unbounded'
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- 'current'

‎generator/config/accumulator/firstN.yaml

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@@ -6,17 +6,52 @@ type:
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- window
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encode: object
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description: |
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Returns a specified number of elements from the beginning of an array. Distinct from the $firstN accumulator.
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Returns an aggregation of the first n elements within a group.
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The elements returned are meaningful only if in a specified sort order.
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If the group contains fewer than n elements, $firstN returns all elements in the group.
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arguments:
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-
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name: input
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type:
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- resolvesToArray
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- expression
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description: |
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An expression that resolves to the array from which to return n elements.
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-
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name: 'n'
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type:
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- resolvesToInt
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description: |
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An expression that resolves to a positive integer. The integer specifies the number of array elements that $firstN returns.
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A positive integral expression that is either a constant or depends on the _id value for $group.
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tests:
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-
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name: 'Null and Missing Values'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/firstN/#null-and-missing-values'
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pipeline:
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-
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$documents:
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-
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playerId: 'PlayerA'
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gameId: 'G1'
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score: 1
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-
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playerId: 'PlayerB'
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gameId: 'G1'
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score: 2
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-
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playerId: 'PlayerC'
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gameId: 'G1'
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score: 3
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-
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playerId: 'PlayerD'
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gameId: 'G1'
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-
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playerId: 'PlayerE'
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gameId: 'G1'
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score: ~
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-
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$group:
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_id: '$gameId'
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firstFiveScores:
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$firstN:
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input: '$score'
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n: 5

‎generator/config/accumulator/last.yaml

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name: expression
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type:
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- expression
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tests:
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-
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name: 'Use in $group Stage'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/last/'
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pipeline:
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-
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$sort:
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item: 1
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date: 1
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-
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$group:
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_id: '$item'
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lastSalesDate:
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$last: '$date'
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-
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name: 'Use in $setWindowFields Stage'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/last/#use-in--setwindowfields-stage'
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pipeline:
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-
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$setWindowFields:
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partitionBy: '$state'
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sortBy:
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orderDate: 1
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output:
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lastOrderTypeForState:
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$last: '$type'
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window:
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documents:
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- 'current'
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- 'unbounded'

‎generator/config/accumulator/lastN.yaml

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name: $lastN
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN/'
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type:
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- accumulator
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- window
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encode: object
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description: |
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Returns a specified number of elements from the end of an array. Distinct from the $lastN accumulator.
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Returns an aggregation of the last n elements within a group.
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The elements returned are meaningful only if in a specified sort order.
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If the group contains fewer than n elements, $lastN returns all elements in the group.
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arguments:
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-
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name: input
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- resolvesToInt
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description: |
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An expression that resolves to a positive integer. The integer specifies the number of array elements that $firstN returns.
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tests:
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-
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name: 'Find the Last Three Player Scores for a Single Game'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN/#find-the-last-three-player-scores-for-a-single-game'
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pipeline:
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-
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$match:
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gameId: 'G1'
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-
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$group:
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_id: '$gameId'
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lastThreeScores:
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$lastN:
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input:
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- '$playerId'
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- '$score'
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n: 3
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-
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name: 'Finding the Last Three Player Scores Across Multiple Games'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN/#finding-the-last-three-player-scores-across-multiple-games'
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pipeline:
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-
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$group:
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_id: '$gameId'
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playerId:
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$lastN:
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input:
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- '$playerId'
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- '$score'
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n: 3
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-
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name: 'Using $sort With $lastN'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN/#using--sort-with--lastn'
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pipeline:
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-
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$sort:
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score: -1
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-
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$group:
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_id: '$gameId'
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playerId:
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$lastN:
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input:
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- '$playerId'
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- '$score'
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n: 3
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-
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name: 'Computing n Based on the Group Key for $group'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN/#computing-n-based-on-the-group-key-for--group'
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pipeline:
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-
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$group:
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_id:
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gameId: '$gameId'
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gamescores:
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$lastN:
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input: '$score'
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n:
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$cond:
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if:
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$eq:
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- '$gameId'
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- 'G2'
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then: 1
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else: 3

‎generator/config/expression/first.yaml

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# $schema: ../schema.json
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name: $first
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/first/'
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type:
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- resolvesToAny
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encode: single
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description: |
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Returns the result of an expression for the first document in an array.
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arguments:
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-
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name: expression
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type:
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- resolvesToArray
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tests:
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-
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name: 'Use in $addFields Stage'
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pipeline:
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-
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$addFields:
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firstItem:
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$first: '$items'

‎generator/config/expression/firstN.yaml

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# $schema: ../schema.json
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name: $firstN
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/firstN-array-element/'
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type:
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- resolvesToArray
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encode: object
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description: |
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Returns a specified number of elements from the beginning of an array.
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arguments:
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-
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name: 'n'
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type:
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- resolvesToInt
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description: |
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An expression that resolves to a positive integer. The integer specifies the number of array elements that $firstN returns.
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-
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name: input
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type:
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- resolvesToArray
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description: |
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An expression that resolves to the array from which to return n elements.
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tests:
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-
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name: Example
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link: https://www.mongodb.com/docs/manual/reference/operator/aggregation/firstN-array-element/#example
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pipeline:
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-
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$addFields:
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firstScores:
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$firstN:
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n: 3
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input: '$score'

‎generator/config/expression/last.yaml

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# $schema: ../schema.json
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name: $last
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/last/'
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type:
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- resolvesToAny
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encode: single
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description: |
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Returns the result of an expression for the last document in an array.
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arguments:
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-
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name: expression
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type:
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- resolvesToArray
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tests:
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-
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name: 'Use in $addFields Stage'
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pipeline:
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-
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$addFields:
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lastItem:
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$last: '$items'

‎generator/config/expression/lastN.yaml

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# $schema: ../schema.json
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name: $lastN
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN-array-element/'
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type:
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- resolvesToArray
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encode: object
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description: |
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Returns a specified number of elements from the end of an array.
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arguments:
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-
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name: 'n'
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type:
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- resolvesToInt
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description: |
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An expression that resolves to a positive integer. The integer specifies the number of array elements that $firstN returns.
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-
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name: input
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type:
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- resolvesToArray
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description: |
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An expression that resolves to the array from which to return n elements.
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tests:
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-
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name: Example
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN-array-element/#example'
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pipeline:
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-
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$addFields:
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lastScores:
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$lastN:
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n: 3
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input: '$score'
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-
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name: 'Using $lastN as an Aggregation Expression'
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link: 'https://www.mongodb.com/docs/manual/reference/operator/aggregation/lastN/#using--lastn-as-an-aggregation-expression'
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pipeline:
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-
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$documents:
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-
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array:
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- 10
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- 20
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- 30
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- 40
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-
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$project:
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lastThreeElements:
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$lastN:
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input: '$array'
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n: 3

‎generator/config/stage/project.yaml

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-
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name: specification
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type:
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- bool
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- int
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- expression
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- projection
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- resolvesToBool
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- object
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variadic: object

‎generator/config/stage/setWindowFields.yaml

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description: |
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Specifies the field(s) to append to the documents in the output returned by the $setWindowFields stage. Each field is set to the result returned by the window operator.
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A field can contain dots to specify embedded document fields and array fields. The semantics for the embedded document dotted notation in the $setWindowFields stage are the same as the $addFields and $set stages.
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-
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name: window
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type:
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- window
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optional: true
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description: |
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Specifies the window boundaries and parameters. Window boundaries are inclusive. Default is an unbounded window, which includes all documents in the partition.

‎src/Builder/Accumulator/FactoryTrait.php

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