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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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110 changes: 110 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 +288,116 @@ 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', () => {
// Edge case: planner is sharded, execution stats may not be
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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10 changes: 10 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 +770,16 @@ export class ExplainPlanAnalyzer {
}
}

// Traverse shard branches (sharded clusters)
if (plan.shards && Array.isArray(plan.shards)) {
for (const shard of plan.shards) {
const found = this.findStageInPlan(shard as Document, stageName);
if (found) {
return found;
}
}
}

return undefined;
}

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6 changes: 6 additions & 0 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 +75,11 @@ export class StagePropertyExtractor {
this.collectPlannerStages(child, accumulator);
});
}
if (stage.shards && Array.isArray(stage.shards)) {
for (const shard of stage.shards) {
this.collectPlannerStages(shard as Document, accumulator);
}
}
}

/**
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