Datagraph Schema

Overview

The Schema page — Design and manage your data model schema — is where the Datagraph data model is built. Open DataHub → Datagraph → Schema. One Datagraph Schema exists per account, with a Draft and a Live version.

Before You Begin

The Datasources you want to model must already exist in the DataHub.
Column names and types are read from the Datasource field mapping, so review the field mapping first.
Publishing requires the update permission on Datagraph Schema.

Editor Layout

Tables, columns, and relations are edited through forms. Two side panels support the work:

Panel	Content
Tables	The tables already defined. Select one to edit it.
Datasources	A searchable list of the account Datasources. Click one to add it as a table.

Preview opens the model as a Diagram, with a zoom Reset control. Open in Explorer hands the model over to the Explorer for validation.

Adding a Table

Click Add table.
Select the Datasource in the Datasource field. The table name always matches the selected Datasource.
Optionally fill the Description to document what the table holds.
Add columns on the Columns tab, then relations on the Relations tab.
Click Save to store the Draft.

Removing a table uses Delete table and asks for confirmation.

Columns

Click Add column on the Columns tab. A column always mirrors a Datasource field.

Field	Description
Name	The column name used in Entity SQL. Must be unique within the table.
Datasource field	The Datasource field feeding the column. Required.
Type	The data type, inherited from the Datasource field mapping (for example `string`, `number`, `price`, `datetime_iso`, `array_string`).
Description	Optional documentation for the column.
Nullable	Whether the column accepts null values.

Add column is disabled when the table has no Datasource yet, or when every Datasource field is already a column. The column list shows the current count, so you can check coverage at a glance.

Optionally, a column can declare a default value. The default must match the column type: a number for a number column, a boolean for a boolean column, a string for a string column.

Relations

Relations are the links the Datagraph joins on. Click Add relation on the Relations tab.

Field	Description
Type	The relation type.
Columns	The columns from this table taking part in the relation.
References → Table	The referenced table. Select it before choosing its columns.
References → Columns	The columns in the referenced table, in the same order as the local columns.

Both sides must list the same number of columns, and every referenced column must exist.

Worked Example

A product catalogue Datasource and a purchases Datasource share a product reference.

Table	Column	Relation
`purchases`	`product_reference`	References `products.reference_id`
`products`	`reference_id`	Declared as a unique key

With that relation in place, an Entity can join purchases to the catalogue and return product names, prices, and images for a person’s past orders.

Validation Errors

Saving validates the whole model. The following definitions are rejected:

Error	Cause
Duplicate table	Two tables point at the same Datasource.
Duplicate column	Two columns in a table share a name, or a virtual column reuses a real column name.
Unknown column	A relation, unique key, or index references a column that does not exist.
Unknown referenced table	A relation points at a table that is not in the model.
Column count mismatch	A relation lists a different number of local and referenced columns.
Invalid default	A column default does not match the column type.

Publishing

Click Publish to promote the Draft. The confirmation dialog states that the Draft version will be promoted to Live. After publishing:

The previous Live version becomes Inactive.
A new Draft copy of the Live definition is created, so editing can continue.
Entity output columns are recomputed against the new Live model.

Structural validity is not the same as data quality. A model can be perfectly valid and still contain relations whose values barely overlap. Check the join match in the Explorer before publishing.

What’s Next?

Explorer

Inspect the diagram and the join match of every relation.

Entities

Query the model and expose the results to Workflows.

Field Mapping

Review how raw Datasource fields become typed fields.