Subject area

Reading data

Reading an object and deciding exactly which fields and references come back: field selection, wildcards, nested references, abstract types, and what happens in the database.

Topics in this subject area

1.Reading an object
How POST /read/{id} and GET /read/{id} work, what comes back for a missing or invisible object, and how singleton and abstract model differ.
2.Field selection with response
The response list decides what comes back, and it is mandatory. This page lists the possible entries and what happens when the list is missing or a field is unknown.
3.Wildcards + and *
How you request many fields at once with + and *, what the partial wildcards name+, +name, name* and *name match, and why * needs more permissions than you might think.
4.Expanding references and lists
How a reference is fully loaded with { field, response }, how lists get their own filter, sorting and page size, and how deep this may go.
5.Reading through abstract types
If a reference points to an abstract model, CDMS returns the fields of all possible subtypes. This page explains how that is resolved and how the client tells the types apart.
6.What happens in the database when reading
The field selection drives the SQL query: only the requested columns, references via LEFT JOIN, no loading in the background. This page explains why this is fast and when it gets expensive.