PCDOE Manage Database Solutions Practice Question

Correct answer & explanation

Firestore automatically creates single-field indexes for scalar values. For array fields, to support array-contains queries, you must create an index exemption to include the array field. Actually, Firestore automatically creates an index for array fields as well, but for queries with array-contains, you need to explicitly create an index exemption to include the array. Wait, the domain says: 'index exemptions (for arrays and maps)'. The default behavior: Firestore automatically creates a single-field index for each field, including arrays. However, for arrays, the index automatically includes the array values. So no exemption needed. Exemptions are to exclude fields from automatic indexing. So if they want to query array-contains, they don't need to do anything special if the field is indexed. But the domain says 'index exemptions (for arrays and maps)' which might mean that arrays and maps are exempted from automatic indexing? Actually, in Firestore, automatic indexing covers all fields including arrays and maps. But you can create index exemptions to exclude certain fields from indexing. For arrays, to use array-contains, the field must be indexed. Since it's automatically indexed, no action is needed. However, the domain says 'index exemptions (for arrays and maps)' — that likely means that arrays and maps are not automatically indexed in Datastore mode? Let me check: In Native mode, all fields are automatically indexed. In Datastore mode, you must define indexes manually. The question says 'Firestore in Native mode', so automatic indexing applies. So the correct answer is that no additional configuration is needed. Option B says 'Create an index exemption for the array field' — that would exclude it from indexing, which is wrong. Option C 'Create a composite index' is not needed for a single array-contains query. Option D 'Use Datastore mode' is not necessary. So A is correct. But wait, the domain mentions 'single-field indexes (automatic), composite indexes (manual), index exemptions (for arrays and maps)'. This suggests that arrays and maps are exempted from automatic indexing by default? Actually, in Firestore Native mode, arrays are indexed as composite indexes? I recall that Firestore automatically indexes each field, including arrays. For array-contains queries, the array field must be indexed; it is by default. So no action needed. However, some sources say that array fields are not indexed automatically. I think the correct answer per GCP documentation is: In Native mode, all fields are automatically indexed. For arrays, the index includes each element. So no action required. So I'll go with A.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.