The minimum length of a partition key and sort key is 1 byte, while the maximum length is 2048 bytes (2048 characters when using String type). What is the maximum length of sort key in DynamoDB? Yes! Number is supported type as DynamoDB key. How do I use numeric id for DynamoDB key? All the attribute names, values, and keys are case sensitive. Similarly to the partition key, sort key cannot be changed after the table is provisioned. You can only provision a new table, move data there, and then remove the first table.
Once the table is setup, you cannot modify its Key Schema. Is it possible to change partition key in DynamoDB?
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Moreover, you cannot update or delete them after table creation while you can do so with GSIs.įrequently Asked Questions What can be a key in DynamoDB?įrom all of the DynamoDB Types, only String, Binary and Number can be used as the key attribute type. After that, you'll start getting ItemCollectionSizeLimitExceededException. LSIs have a maximum size of collection - 10 GB. Favor GSIs (Global Secondary Indexes) over LSIs (Local Secondary Indexes).This way they'll fit for multiple use cases and you'll be able to adapt to the new business requirements without altering your table definition. Prefer generic GSI attribute names, something like gsi1_pk, gsi2_sk, etc.For most applications, three GSIs are enough. This is especially important if you're going with Single-Table design. Plan your access patterns first, so you'll know what GSIs to create.This will reduce the likelihood of throttling Isolate frequently accessed items so they won't reside on the same partition. Use keys with high cardinality to avoid hot keys/partitions problem.They enable you sorting within one partition, they enable filtering without using FilterExpressions They offer more functionality without downsides. Favor composite keys over simple keys.It causes an intensified load on one of the partitions, while others are accessed much less often. What is a hot key? It's an item with the key that is accessed much more frequently than the rest of the items. If your application will not access the keyspace uniformly, you might encounter the hot partition problem also known as hot key. If you create a table with Local Secondary Index, that table is going to have a 10GB size limit per partition key value.Ĭhoosing the right keys is essential to keep your DynamoDB tables fast and performant.All LSIs must be specified on table creation. Unlike GSIs, you cannot update or delete them after table creation.Generally speaking, you should rather avoid LSIs for two reasons: This is useful if you need to be able to fetch a collection of items sorted based on more than one attribute, e.g. In LSIs, the partition key must remain the same as the primary key's partition key. It works similar to the GSI but with one difference. DynamoDB Local Secondary Index (LSI)Īnother variation of secondary key is the Local Secondary Index. When a mutation is made against the table, any of the global secondary indexes on that table are updated asynchronously in an eventually consistent manner.
In the background, DynamoDB keeps each of the GSIs automatically in sync with the base table. With GSIs, you can use GetItem and query operations using non-primary key attributes. If you index that attribute using Global Secondary Index, you don't have to use scan operation. DynamoDB Global Secondary Index (GSI)īut what if you want to fetch an item without knowing its key, you only know other attribute, let's say authorId of the Book. Thanks to that (and GSIs + LSIs, more on that later), our Key-Value store becomes much more sophisticated because it allows for more complex query access patterns. Choosing this option allows items to share the same partition/hash key, but the combination of hash key and sort key must be unique.Īs a consequence, you can now use Query, which allows to fetch a collection of items with the same partition key. DynamoDB Composite KeyĪnother option is to use a composite key, which is composed of partition key, also known as hash key, and sort key, also known as range key.
You lose the ability to perform a Query, to fetch data from a table with such key, you can use Scan or GetItem operation. With simple key, DynamoDB essentially works just like a Key-Value store. Each record needs to have one of these, and it needs to be unique. In DynamoDB there are two types of primary keys: Different DynamoDB Key TypesĭynamoDB simple key consists only of one value - the partition/hash key.
If you want to access an item in the DynamoDB table fast (with O(1) complexity), you'll need to know its key. Keys, like in many other NoSQL and SQL databases, act as a unique identifier of a record or item.
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