Index projection types (ALL, KEYS_ONLY, INCLUDE) in DynamoDB - Step-by-Step Execution

Concept Flow - Index projection types (ALL, KEYS_ONLY, INCLUDE)

Start: Query on GSI/LSI

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Check Projection Type

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ALL

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Return all attributes

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Result Set

When querying a secondary index, DynamoDB checks the projection type to decide which attributes to return: all attributes, only keys, or keys plus some included attributes.

Execution Sample

DynamoDB

Query GSI with ProjectionType = ALL
Query GSI with ProjectionType = KEYS_ONLY
Query GSI with ProjectionType = INCLUDE (attr1, attr2)

Shows how DynamoDB returns different sets of attributes based on the index's projection type during a query.

Execution Table

Step	Projection Type	Attributes Requested	Attributes Returned	Notes
1	ALL	PartitionKey, SortKey, AttrA, AttrB, AttrC	PartitionKey, SortKey, AttrA, AttrB, AttrC	Returns all attributes from the base table
2	KEYS_ONLY	PartitionKey, SortKey, AttrA, AttrB, AttrC	PartitionKey, SortKey	Returns only the keys of the index
3	INCLUDE	PartitionKey, SortKey, AttrA, AttrB, AttrC	PartitionKey, SortKey, AttrA, AttrB	Returns keys plus included attributes AttrA and AttrB
4	INCLUDE	PartitionKey, SortKey, AttrA, AttrB, AttrC	PartitionKey, SortKey, AttrA	If only AttrA included, returns keys plus AttrA
5	KEYS_ONLY	PartitionKey, SortKey	PartitionKey, SortKey	Query only keys, no other attributes
6	-	-	-	Query ends after returning projected attributes

💡 Query completes after returning attributes based on the projection type.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
Attributes Returned	None	All attributes	Only keys	Keys + included attrs	Keys + included attrs or keys only

Key Moments - 3 Insights

Why does a KEYS_ONLY projection return fewer attributes than ALL?

Because KEYS_ONLY projection returns only the partition and sort keys of the index, not the other attributes, as shown in execution_table row 2.

What happens if you query an index with INCLUDE projection but request attributes not included?

Only the keys and the explicitly included attributes are returned; other attributes are not available from the index, as shown in execution_table row 3.

Does ALL projection return attributes not present in the base table?

No, ALL projection returns all attributes from the base table for the items in the index, as shown in execution_table row 1.

Visual Quiz - 3 Questions

Look at the execution table, what attributes are returned at step 2 with KEYS_ONLY projection?

A Only partition and sort keys

B All attributes including keys

C Keys plus included attributes

D No attributes

💡 Hint

Refer to execution_table row 2 under 'Attributes Returned'

At which step does the query return keys plus some included attributes?

A Step 1

B Step 3

C Step 2

D Step 5

💡 Hint

Check execution_table rows for 'INCLUDE' projection type

If you want to get all attributes from the base table via an index, which projection type should you use?

A KEYS_ONLY

B INCLUDE

C ALL

D None

💡 Hint

See execution_table row 1 for ALL projection

Concept Snapshot

Index Projection Types in DynamoDB:
- ALL: Returns all attributes from the base table.
- KEYS_ONLY: Returns only the index keys (partition and sort keys).
- INCLUDE: Returns keys plus specified non-key attributes.
Choose projection type based on query needs and storage cost.

Full Transcript

When you query a DynamoDB secondary index, the database decides which attributes to return based on the index's projection type. There are three types: ALL returns every attribute from the base table, KEYS_ONLY returns only the partition and sort keys, and INCLUDE returns the keys plus some extra attributes you specify. This choice affects what data you get back and how much storage the index uses. The execution table shows step-by-step what attributes are returned for each projection type during queries.