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/**
* Test the behavior of $first.
*/
(function() {
"use strict";
load("jstests/aggregation/extras/window_function_helpers.js");
const coll = db[jsTestName()];
coll.drop();
// Create a collection of tickers and prices.
const nDocsPerTicker = 10;
seedWithTickerData(coll, nDocsPerTicker);
// Run the suite of partition and bounds tests against the $first function.
testAccumAgainstGroup(coll, "$first");
// Like most other window functions, the default window for $first is [unbounded, unbounded].
coll.drop();
assert.commandWorked(coll.insert([
{x: 0, y: 0},
{x: 1, y: 42},
{x: 2, y: 67},
{x: 3, y: 99},
{x: 4, y: 20},
]));
let result = coll.aggregate([
{
$setWindowFields: {
sortBy: {x: 1},
output: {
first: {$first: "$y"},
}
}
},
{$unset: "_id"},
])
.toArray();
assert.sameMembers(result, [
{x: 0, y: 0, first: 0},
{x: 1, y: 42, first: 0},
{x: 2, y: 67, first: 0},
{x: 3, y: 99, first: 0},
{x: 4, y: 20, first: 0},
]);
// A default value of NULL is returned if there is no first document.
coll.drop();
assert.commandWorked(coll.insert([
{x: 1, y: 5},
{x: 2, y: 4},
{x: 3, y: 6},
{x: 4, y: 5},
]));
result = coll.aggregate([
{
$setWindowFields: {
sortBy: {x: 1},
partitionBy: "$x",
output: {
first: {$first: "$y", window: {documents: [-1, -1]}},
}
}
},
{$unset: "_id"},
])
.toArray();
assert.sameMembers(result, [
{x: 1, y: 5, first: null},
{x: 2, y: 4, first: null},
{x: 3, y: 6, first: null},
{x: 4, y: 5, first: null},
]);
// Nonobject window fields cause parse errors
result = coll.runCommand({
explain: {
aggregate: coll.getName(),
cursor: {},
pipeline: [
{
$setWindowFields: {
sortBy: {x: 1},
output: {
first: {$first: "$y", window: [0, 1]},
}
}
},
]
}
});
assert.commandFailedWithCode(result, ErrorCodes.FailedToParse, "'window' field must be an object");
})();
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