feat: Implement $top and $bottom accumulator operators.

kofrasa · Dec 13, 2022 · 9c4e914 · 9c4e914
1 parent 053db02
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diff --git a/src/operators/accumulator/bottom.ts b/src/operators/accumulator/bottom.ts
@@ -0,0 +1,20 @@
+// https://www.mongodb.com/docs/manual/reference/operator/aggregation/bottom/#mongodb-group-grp.-bottom
+import { Options } from "../../core";
+import { AnyVal, RawObject } from "../../types";
+import { $bottomN } from "./bottomN";
+
+/**
+ * Returns the bottom element within a group according to the specified sort order.
+ *
+ * @param {Array} collection The input array
+ * @param {Object} expr The right-hand side expression value of the operator
+ * @param {Options} options The options to use for this operation
+ * @returns {*}
+ */
+export function $bottom(
+  collection: RawObject[],
+  expr: { sortBy: Record<string, number>; output: AnyVal },
+  options?: Options
+): AnyVal[] {
+  return $bottomN(collection, { ...expr, n: 1 }, options);
+}
diff --git a/src/operators/accumulator/index.ts b/src/operators/accumulator/index.ts
@@ -5,6 +5,7 @@
 export * from "./accumulator";
 export * from "./addToSet";
 export * from "./avg";
+export * from "./bottom";
 export * from "./bottomN";
 export * from "./count";
 export * from "./covariancePop";
@@ -18,4 +19,5 @@ export * from "./push";
 export * from "./stdDevPop";
 export * from "./stdDevSamp";
 export * from "./sum";
+export * from "./top";
 export * from "./topN";
diff --git a/src/operators/accumulator/top.ts b/src/operators/accumulator/top.ts
@@ -0,0 +1,20 @@
+// https://www.mongodb.com/docs/manual/reference/operator/aggregation/top/#mongodb-group-grp.-top
+import { Options } from "../../core";
+import { AnyVal, RawObject } from "../../types";
+import { $topN } from "./topN";
+
+/**
+ * Returns the top element within a group according to the specified sort order.
+ *
+ * @param {Array} collection The input array
+ * @param {Object} expr The right-hand side expression value of the operator
+ * @param {Options} options The options to use for this operation
+ * @returns {*}
+ */
+export function $top(
+  collection: RawObject[],
+  expr: { sortBy: Record<string, number>; output: AnyVal },
+  options?: Options
+): AnyVal[] {
+  return $topN(collection, { ...expr, n: 1 }, options);
+}
diff --git a/test/operators/accumulator/bottom.test.ts b/test/operators/accumulator/bottom.test.ts
@@ -0,0 +1,120 @@
+import * as samples from "../../support";
+
+const docs = [
+  { playerId: "PlayerA", gameId: "G1", score: 31 },
+  { playerId: "PlayerB", gameId: "G1", score: 33 },
+  { playerId: "PlayerC", gameId: "G1", score: 99 },
+  { playerId: "PlayerD", gameId: "G1", score: 1 },
+  { playerId: "PlayerA", gameId: "G2", score: 10 },
+  { playerId: "PlayerB", gameId: "G2", score: 14 },
+  { playerId: "PlayerC", gameId: "G2", score: 66 },
+  { playerId: "PlayerD", gameId: "G2", score: 80 },
+];
+
+samples.runTestPipeline("operators/accumulator/bottom", [
+  {
+    message: "Null and Missing Values",
+    input: [
+      { playerId: "PlayerA", gameId: "G1", score: 1 },
+      { playerId: "PlayerB", gameId: "G1", score: 2 },
+      { playerId: "PlayerC", gameId: "G1", score: 3 },
+      { playerId: "PlayerD", gameId: "G1" },
+      { playerId: "PlayerE", gameId: "G1", score: null },
+    ],
+    pipeline: [
+      {
+        $group: {
+          _id: "$gameId",
+          playerId: {
+            $bottom: {
+              output: ["$playerId", "$score"],
+              sortBy: { score: -1 },
+            },
+          },
+        },
+      },
+    ],
+    expected: [
+      {
+        _id: "G1",
+        playerId: [["PlayerE", null]],
+      },
+    ],
+  },
+  {
+    message: "Data Type Sort Ordering",
+    input: [
+      { playerId: "PlayerA", gameId: "G1", score: 1 },
+      { playerId: "PlayerB", gameId: "G1", score: "2" },
+      { playerId: "PlayerC", gameId: "G1", score: "" },
+    ],
+    pipeline: [
+      {
+        $group: {
+          _id: "$gameId",
+          playerId: {
+            $bottom: {
+              output: ["$playerId", "$score"],
+              sortBy: { score: -1 },
+            },
+          },
+        },
+      },
+    ],
+    expected: [
+      {
+        _id: "G1",
+        playerId: [["PlayerA", 1]],
+      },
+    ],
+  },
+
+  {
+    message: "Finding the Three Lowest Score Documents Across Multiple Games",
+    input: docs,
+    pipeline: [
+      {
+        $group: {
+          _id: "$gameId",
+          playerId: {
+            $bottom: {
+              output: ["$playerId", "$score"],
+              sortBy: { score: -1 },
+            },
+          },
+        },
+      },
+    ],
+    expected: [
+      {
+        _id: "G1",
+        playerId: [["PlayerD", 1]],
+      },
+      {
+        _id: "G2",
+        playerId: [["PlayerA", 10]],
+      },
+    ],
+  },
+  {
+    message: "Computing n Based on the Group Key for $group",
+    input: docs,
+    pipeline: [
+      {
+        $group: {
+          _id: { gameId: "$gameId" },
+          gamescores: {
+            $bottom: {
+              output: "$score",
+              sortBy: { score: -1 },
+            },
+          },
+        },
+      },
+    ],
+    expected: [
+      { _id: { gameId: "G1" }, gamescores: [1] },
+      { _id: { gameId: "G2" }, gamescores: [10] },
+    ],
+  },
+]);
diff --git a/test/operators/accumulator/top.test.ts b/test/operators/accumulator/top.test.ts
@@ -0,0 +1,92 @@
+import * as samples from "../../support";
+
+const docs = [
+  { playerId: "PlayerA", gameId: "G1", score: 31 },
+  { playerId: "PlayerB", gameId: "G1", score: 33 },
+  { playerId: "PlayerC", gameId: "G1", score: 99 },
+  { playerId: "PlayerD", gameId: "G1", score: 1 },
+  { playerId: "PlayerA", gameId: "G2", score: 10 },
+  { playerId: "PlayerB", gameId: "G2", score: 14 },
+  { playerId: "PlayerC", gameId: "G2", score: 66 },
+  { playerId: "PlayerD", gameId: "G2", score: 80 },
+];
+samples.runTestPipeline("operators/accumulator/top", [
+  {
+    message: "Null and Missing Values",
+    input: [
+      { playerId: "PlayerA", gameId: "G1", score: 1 },
+      { playerId: "PlayerB", gameId: "G1", score: 2 },
+      { playerId: "PlayerC", gameId: "G1", score: 3 },
+      { playerId: "PlayerD", gameId: "G1" },
+      { playerId: "PlayerE", gameId: "G1", score: null },
+    ],
+    pipeline: [
+      {
+        $group: {
+          _id: "$gameId",
+          playerId: {
+            $top: {
+              output: ["$playerId", "$score"],
+              sortBy: { score: 1 },
+            },
+          },
+        },
+      },
+    ],
+    expected: [
+      {
+        _id: "G1",
+        playerId: [["PlayerD", undefined]],
+      },
+    ],
+  },
+  {
+    message: "Data Type Sort Ordering",
+    input: [
+      { playerId: "PlayerA", gameId: "G1", score: 1 },
+      { playerId: "PlayerB", gameId: "G1", score: "2" },
+      { playerId: "PlayerC", gameId: "G1", score: "" },
+    ],
+    pipeline: [
+      {
+        $group: {
+          _id: "$gameId",
+          playerId: {
+            $top: {
+              output: ["$playerId", "$score"],
+              sortBy: { score: -1 },
+            },
+          },
+        },
+      },
+    ],
+    expected: [
+      {
+        _id: "G1",
+        playerId: [["PlayerB", "2"]],
+      },
+    ],
+  },
+
+  {
+    message: "Find the Top Score Across Multiple Games",
+    input: docs,
+    pipeline: [
+      {
+        $group: {
+          _id: "$gameId",
+          playerId: {
+            $top: {
+              output: ["$playerId", "$score"],
+              sortBy: { score: -1 },
+            },
+          },
+        },
+      },
+    ],
+    expected: [
+      { _id: "G1", playerId: [["PlayerC", 99]] },
+      { _id: "G2", playerId: [["PlayerD", 80]] },
+    ],
+  },
+]);