Projection REST API

Projections have a dedicated query endpoint plus metadata endpoints under /api/dereg.

Query a Projection

Method	Route
GET	/api/projections/{name}/query

Query parameters:

• limit optional, default 1000
• offset optional, default 0

Behavior:

• Validates projection name as an identifier
• Confirms the projection exists in DeReg
• Reads query_sql from DESCRIBE PROJECTION {name}
• Executes that SQL with appended pagination
• Returns Arrow IPC

Projection Metadata

Method	Route
GET	/api/dereg/projections
GET	/api/dereg/projections/{name}

Creating Projections

Use the optional schema API:

Method	Route
POST	/api/deql/create

with a CREATE PROJECTION ... statement.

Errors

Status	Meaning
400	Invalid identifier
404	Projection not found
500	Missing query_sql or execution failure