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// Tests the behavior of explain() when used with the aggregation pipeline and limits.
// @tags: [do_not_wrap_aggregations_in_facets]
(function() {
"use strict";
load("jstests/libs/analyze_plan.js"); // For getAggPlanStages().
let coll = db.explain_limit;
const kMultipleSolutionLimit = 101;
const kCollSize = kMultipleSolutionLimit + 5;
const kLimit = 10;
// Return whether or explain() was successful and contained the appropriate fields given the
// requested verbosity. Checks that the number of documents examined is correct based on
// 'multipleSolutions', which indicates there was more than one plan available.
function checkResults({results, verbosity, multipleSolutions}) {
let cursorSubdocs = getAggPlanStages(results, "$cursor");
assert.gt(cursorSubdocs.length, 0);
for (let stageResult of cursorSubdocs) {
assert(stageResult.hasOwnProperty("$cursor"));
let result = stageResult.$cursor;
assert.eq(result.limit, NumberLong(kLimit), tojson(results));
if (verbosity === "queryPlanner") {
assert(!result.hasOwnProperty("executionStats"), tojson(results));
} else {
// If it's "executionStats" or "allPlansExecution".
if (multipleSolutions) {
// If there's more than one plan available, we may run several of them against
// each other to see which is fastest. During this, our limit may be ignored
// and so explain may return that it examined more documents than we asked it
// to.
assert.lte(
result.executionStats.nReturned, kMultipleSolutionLimit, tojson(results));
assert.lte(result.executionStats.totalDocsExamined,
kMultipleSolutionLimit,
tojson(results));
} else {
assert.eq(result.executionStats.nReturned, kLimit, tojson(results));
assert.eq(result.executionStats.totalDocsExamined, kLimit, tojson(results));
}
}
}
}
// explain() should respect limit.
coll.drop();
assert.commandWorked(coll.createIndex({a: 1}));
for (let i = 0; i < kCollSize; i++) {
assert.writeOK(coll.insert({a: 1}));
}
const pipeline = [{$match: {a: 1}}, {$limit: kLimit}];
let plannerLevel = coll.explain("queryPlanner").aggregate(pipeline);
checkResults({results: plannerLevel, verbosity: "queryPlanner"});
let execLevel = coll.explain("executionStats").aggregate(pipeline);
checkResults({results: execLevel, verbosity: "executionStats", multipleSolutions: false});
let allPlansExecLevel = coll.explain("allPlansExecution").aggregate(pipeline);
checkResults(
{results: allPlansExecLevel, verbosity: "allPlansExecution", multipleSolutions: false});
// Create a second index so that more than one plan is available.
assert.commandWorked(coll.createIndex({a: 1, b: 1}));
plannerLevel = coll.explain("queryPlanner").aggregate(pipeline);
checkResults({results: plannerLevel, verbosity: "queryPlanner"});
execLevel = coll.explain("executionStats").aggregate(pipeline);
checkResults({results: execLevel, verbosity: "executionStats", multipleSolutions: true});
allPlansExecLevel = coll.explain("allPlansExecution").aggregate(pipeline);
checkResults(
{results: allPlansExecLevel, verbosity: "allPlansExecution", multipleSolutions: true});
})();
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