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fix(query-insights): traverse shard branches in planner-tree helpers #703

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fix(query-insights): traverse shard branches in planner-tree helpers #703

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hanhan761 May 29, 2026
26de0e4
fix: address Copilot review feedback for shard traversal in query-ins…
hanhan761 Jun 2, 2026
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115 changes: 115 additions & 0 deletions src/documentdb/queryInsights/ExplainPlanAnalyzer.addIndexStrategyAdvisories.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -288,6 +288,121 @@ describe('ExplainPlanAnalyzer.addIndexStrategyAdvisories', () => {
});
});

it('detects isBitmap under a shard branch in the winning plan', () => {
// Simulates a sharded cluster where the IXSCAN with isBitmap lives
// under a SHARD_MERGE > shards > FETCH > IXSCAN path.
// Before the fix, findStageInPlan() did not recurse into shards.
const analysis = makeAnalysis();
const explainResult: Document = {
queryPlanner: {
winningPlan: {
stage: 'SHARD_MERGE',
shards: [
{
stage: 'SINGLE_SHARD',
inputStage: {
stage: 'FETCH',
inputStage: {
stage: 'IXSCAN',
indexName: 'bitmapIndex_1',
isBitmap: true,
},
},
},
],
},
},
executionStats: {
nReturned: 100,
executionTimeMillis: 13,
totalDocsExamined: 100,
totalKeysExamined: 100,
executionStages: {
stage: 'SHARD_MERGE',
shards: [
{
stage: 'SINGLE_SHARD',
inputStage: {
stage: 'FETCH',
inputStage: {
stage: 'IXSCAN',
indexName: 'bitmapIndex_1',
indexUsage: [
{
scanKeys: [
'key 1: [(isInequality: false, estimatedEntryCount: 100)]',
],
},
],
},
},
},
],
},
},
};

ExplainPlanAnalyzer.addIndexStrategyAdvisories(analysis, 1000, explainResult);

const ids = getDiagnosticIds(analysis.performanceRating.diagnostics);
expect(ids).toContain('bitmap_index');
});

it('detects IXSCAN in planner shards even when exec stats use flat structure', () => {
// Verifies that bitmap index detection works when the queryPlanner
// includes shard info (SHARD_MERGE > SINGLE_SHARD > IXSCAN) but
// executionStats use a simplified flat structure (FETCH > IXSCAN)
// without shard wrappers. This is important because production
// sharded clusters may return plan trees in either format, and the
// bitmap detector must be able to traverse both shapes correctly.
const analysis = makeAnalysis();
const explainResult: Document = {
queryPlanner: {
winningPlan: {
stage: 'SHARD_MERGE',
shards: [
{
stage: 'SINGLE_SHARD',
inputStage: {
stage: 'FETCH',
inputStage: {
stage: 'IXSCAN',
indexName: 'bitmapIndex_1',
isBitmap: true,
},
},
},
],
},
},
executionStats: {
nReturned: 100,
executionTimeMillis: 13,
totalDocsExamined: 100,
totalKeysExamined: 100,
executionStages: {
stage: 'FETCH',
inputStage: {
stage: 'IXSCAN',
indexName: 'bitmapIndex_1',
indexUsage: [
{
scanKeys: [
'key 1: [(isInequality: false, estimatedEntryCount: 100)]',
],
},
],
},
},
},
};

ExplainPlanAnalyzer.addIndexStrategyAdvisories(analysis, 1000, explainResult);

const ids = getDiagnosticIds(analysis.performanceRating.diagnostics);
expect(ids).toContain('bitmap_index');
});

describe('cumulative advisory demotions', () => {
it('demotes score twice when both bitmap and severe multikey thresholds are met', () => {
// Single-field bitmap with 50% coverage + 25× multikey expansion
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13 changes: 13 additions & 0 deletions src/documentdb/queryInsights/ExplainPlanAnalyzer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -770,6 +770,19 @@ export class ExplainPlanAnalyzer {
}
}

// Traverse shard branches (sharded clusters)
if (plan.shards) {
const shardEntries = Array.isArray(plan.shards) ? plan.shards : Object.values(plan.shards);
for (const shardEntry of shardEntries) {
const shard = shardEntry as Document;
const planRoot = shard.winningPlan || shard.executionStages || shard.inputStage || shard;
const found = this.findStageInPlan(planRoot, stageName);
if (found) {
return found;
}
}
}

return undefined;
}

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18 changes: 15 additions & 3 deletions src/documentdb/queryInsights/StagePropertyExtractor.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ export class StagePropertyExtractor {

/**
* Collects all stages from the queryPlanner winning plan tree into a flat array.
* Traverses single inputStage, multiple inputStages, and shard branches (sharded clusters).
*/
private static collectPlannerStages(stage: Document, accumulator: Document[]): void {
if (!stage || !stage.stage) {
Expand All @@ -74,6 +75,14 @@ export class StagePropertyExtractor {
this.collectPlannerStages(child, accumulator);
});
}
if (stage.shards) {
const shardEntries = Array.isArray(stage.shards) ? stage.shards : Object.values(stage.shards);
for (const shardEntry of shardEntries) {
const shard = shardEntry as Document;
const planRoot = shard.winningPlan || shard;
this.collectPlannerStages(planRoot, accumulator);
}
}
}

/**
Expand Down Expand Up @@ -105,9 +114,12 @@ export class StagePropertyExtractor {
});
}
if (stage.shards) {
(stage.shards as Document[]).forEach((shard: Document) => {
this.traverseStages(shard, accumulator);
});
const shardEntries = Array.isArray(stage.shards) ? stage.shards : Object.values(stage.shards);
for (const shardEntry of shardEntries) {
const shard = shardEntry as Document;
const planRoot = shard.executionStages || shard.inputStage || shard;
this.traverseStages(planRoot, accumulator);
}
}
}

Expand Down