Question 1

What changes when Redshift is serverless?

Accepted Answer

Standard Redshift takes a host, port and database user, optionally over SSH, and accepts an access key or an IAM role for S3. Serverless uses IAM role authorization, identifies a workgroup, database and region, and connects through either the Redshift Data API or a Serverless VPC endpoint. Bind the IAM role to a Redshift database role and allow Redshift to assume it.

Question 2

How do MongoDB documents land in a warehouse table?

Accepted Answer

Top level fields become columns. Embedded documents and arrays each become a single JSON valued column rather than being expanded into separate columns, because schema inference here is deliberately non-recursive. If you want something like address.city as its own column, unwind it in the model or derive it in the warehouse afterwards.

Question 3

Which fields will I actually be offered?

Accepted Answer

Whatever appears in a sample of the hundred most recent documents in the collection. A field that only exists on older documents, or on a rare document shape, will not be offered until it turns up in a later sample and you refresh the schema. This surprises people coming from a relational source, where the schema is declared rather than inferred.

Question 4

What if the same field holds different types?

Accepted Answer

Polytomic does not construct a union type. Inference keeps the first usable type it encounters in the sample, so a field that is sometimes a string and sometimes a number lands as whichever it saw first. Heterogeneous collections usually need normalising before they are much use in a data warehouse.

Question 5

Is an S3 bucket still needed?

Accepted Answer

Yes, and in the same region. Both standard Redshift and Serverless stage loads through S3. Serverless removes the cluster you would otherwise size, not the staging storage.

Sync MongoDB to Redshift Serverless

Sync MongoDB to Redshift Serverless with Polytomic

IAM role authorization

Documents as JSON columns

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