mirror of https://github.com/mongodb/mongo
96 lines
4.1 KiB
JavaScript
96 lines
4.1 KiB
JavaScript
// Tests that an aggregation that only needs a finite set of fields to do its computations can
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// sometimes use the query system to provide a covered plan which only returns those fields without
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// fetching the full document.
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//
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// Relies on the initial $match being pushed into the query system in order for the planner to
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// consider an index scan, so the pipelines cannot be wrapped in facet stages.
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// @tags: [
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// do_not_wrap_aggregations_in_facets,
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// ]
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(function() {
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"use strict";
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load("jstests/libs/analyze_plan.js"); // For 'aggPlanHasStage' and other explain helpers.
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const coll = db.use_query_projection;
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coll.drop();
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const bulk = coll.initializeUnorderedBulkOp();
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for (let i = 0; i < 100; ++i) {
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bulk.insert({_id: i, x: "string", a: -i, y: i % 2});
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}
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assert.commandWorked(bulk.execute());
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function assertQueryCoversProjection(
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{pipeline = [], pipelineOptimizedAway = true, options = {}} = {}) {
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const explainOutput = coll.explain().aggregate(pipeline, options);
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if (pipelineOptimizedAway) {
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assert(isQueryPlan(explainOutput), explainOutput);
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assert(!planHasStage(db, explainOutput, "FETCH"), explainOutput);
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assert(planHasStage(db, explainOutput, "IXSCAN"), explainOutput);
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} else {
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assert(isAggregationPlan(explainOutput), explainOutput);
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assert(!aggPlanHasStage(explainOutput, "FETCH"), explainOutput);
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assert(aggPlanHasStage(explainOutput, "IXSCAN"), explainOutput);
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}
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assert(!hasRejectedPlans(explainOutput), explainOutput);
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return explainOutput;
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}
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function assertQueryDoesNotCoverProjection({pipeline = [], pipelineOptimizedAway = true} = {}) {
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const explainOutput = coll.explain().aggregate(pipeline);
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if (pipelineOptimizedAway) {
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assert(isQueryPlan(explainOutput), explainOutput);
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assert(planHasStage(db, explainOutput, "FETCH") || aggPlanHasStage("COLLSCAN"),
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explainOutput);
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} else {
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assert(isAggregationPlan(explainOutput), explainOutput);
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assert(aggPlanHasStage(explainOutput, "FETCH") || aggPlanHasStage("COLLSCAN"),
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explainOutput);
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}
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assert(!hasRejectedPlans(explainOutput), explainOutput);
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return explainOutput;
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}
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assert.commandWorked(coll.createIndex({x: 1, a: -1, _id: 1}));
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// Test that a pipeline requiring a subset of the fields in a compound index can use that index
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// to cover the query.
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assertQueryCoversProjection({pipeline: [{$match: {x: "string"}}, {$project: {_id: 1, x: 1}}]});
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assertQueryCoversProjection({pipeline: [{$match: {x: "string"}}, {$project: {_id: 0, x: 1}}]});
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assertQueryCoversProjection(
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{pipeline: [{$match: {x: "string"}}, {$project: {_id: 0, x: 1, a: 1}}]});
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assertQueryCoversProjection(
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{pipeline: [{$match: {x: "string"}}, {$project: {_id: 1, x: 1, a: 1}}]});
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assertQueryCoversProjection({
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pipeline: [{$match: {_id: 0, x: "string"}}, {$project: {_id: 1, x: 1, a: 1}}],
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options: {hint: {x: 1, a: -1, _id: 1}}
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});
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// Test that a pipeline requiring a field that is not in the index cannot use a covered plan.
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assertQueryDoesNotCoverProjection({pipeline: [{$match: {x: "string"}}, {$project: {notThere: 1}}]});
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// Test that a covered plan is the only plan considered, even if another plan would be equally
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// selective. Add an equally selective index, then rely on assertQueryCoversProjection() to
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// assert that there is only one considered plan, and it is a covered plan.
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assert.commandWorked(coll.createIndex({x: 1}));
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assertQueryCoversProjection({
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pipeline: [
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{$match: {_id: 0, x: "string"}},
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{$sort: {x: 1, a: 1}}, // Note: not indexable, but doesn't add any additional dependencies.
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{$project: {_id: 1, x: 1, a: 1}},
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],
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options: {hint: {x: 1, a: -1, _id: 1}}
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});
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// Test that a multikey index will prevent a covered plan.
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assert.commandWorked(coll.dropIndex({x: 1})); // Make sure there is only one plan considered.
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assert.commandWorked(coll.insert({x: ["an", "array!"]}));
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assertQueryDoesNotCoverProjection(
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{pipeline: [{$match: {x: "string"}}, {$project: {_id: 1, x: 1}}]});
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assertQueryDoesNotCoverProjection(
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{pipeline: [{$match: {x: "string"}}, {$project: {_id: 1, x: 1, a: 1}}]});
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}());
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