The Columns step decides which columns a Lake table keeps, what each one stores, and how it loads. Open it whenever a column needs a type, a key, a statement, a description or a permission change.
Reading the step needs View Lake Objects; saving needs Add/Modify Lake Objects. See Who can do what in the Lake.
| Column | What it holds |
|---|---|
| Name | The column name, as the source reports it. Read-only. |
| Data Domain | The business type of the column, such as Amount or Email. |
| Data Type | The storage type behind the domain. |
| PII Domain | The kind of personal data the column holds. |
| PK | Marks the column as part of the table's primary key. The tooltip reads Primary Key. |
| SY | Whether the column is synchronised with each load. |
| MI | Whether the column is created in the Lake. |
| Permission Group | The permission groups that can read the column. |
| Statement | A SQL expression applied to the column during each load. |
| Source Type | The type the source reports. Read-only. |
Some rows come from the source locked. They show a lock icon, and hovering it reads "This column is locked and cannot be edited." Locked rows cannot be edited at all, including their PII Domain. Name and Source Type are read-only in every row, because they mirror source metadata. A table that reports no columns shows the empty message "No columns defined."
Tick PK on the column or columns that identify each row. A table needs at least one primary key column before it can be deployed, so set this up before your first deploy.
Ctrl+Space. Clear empties the expression, and Cancel closes without saving.The hint under the title reads "Enter a SQL expression for this column. Use Ctrl+Space for column and function suggestions." Expand Column expression · e.g. CAST(amount AS Decimal(18, 2)) for the reminder: "SQL expression applied to compute or transform this column during synchronization."
-. Hover the cell to copy the expression with the copy control.In the Permission Group cell, choose the groups that can read the column. The groups come from the table's General step.
The toolbar above the grid offers two helpers. Each opens a prompt box, and its results land in the grid as unsaved changes; review them and click Apply.
If a helper fails, nothing changes and the toast reads "Failed to generate column comments" or "Failed to suggest primary key".
Drag a column row to move it in the grid. Locked columns cannot be dragged, so they keep their place. The new order is saved when you click Apply.
Apply saves the step; Revert discards the changes. When you save, the grid checks:
Name and name clash.A failed check shows the Validation Error toast with the message (or "Please check the columns configuration."). A successful save reads "Columns saved successfully"; when the save fails for another reason, the toast shows the server's message, or "Failed to save columns". In the rare case that the table has no saved id, the save stops with "Table ID is required for saving columns."
A type change that would turn stored values into NULL is refused with the Type change refused toast. It names the column, the number of values that cannot be converted and an example, and it stays on screen for about 15 seconds. Nothing is saved. To make the change, truncate the table and reload it afterwards; see Run, stop and troubleshoot loads.
Data Type is editable only while the column's Data Domain is Custom. Point at the locked cell to read "Only custom data domain's data type can be edited." To set your own type, choose Custom first. On a locked row, no cell can be edited.
A primary key or partition column always keeps both ticked, and their boxes are locked. The tooltip reads "Sync and migrated must be enabled for primary key or partition columns." On other rows you can change them.
Yes. MI writes both boxes: ticking it also ticks SY, and clearing it also clears SY. SY is looser: ticking SY also ticks MI, while clearing SY leaves MI as it is.
It is a SQL expression applied to compute or transform the column during each load, such as concat("first_name", ' ', "last_name"). Click the Statement cell to edit it, and use Ctrl+Space for column and function suggestions.
Sync Schema found that the source now maps the column to a different type, while the Lake table keeps the type it has. Hover the amber cell to read "Source now maps to {new type}; the Lake column is {current type}". See Run, stop and troubleshoot loads for Sync Schema.
The change would turn existing stored values into NULL, so the platform refuses it and nothing is saved. The Type change refused message names the column, how many values cannot be converted and an example. To apply the change, truncate the table and reload it afterwards; see Run, stop and troubleshoot loads.
Any column that is open for editing. Locked columns cannot be dragged. The new order is saved when you click Apply.
From the table's General step, in Permission Groups. The admin group always has full access and is not added per column. With no groups on the table, the cell reads "No permission groups added to table" and offers Add in General. You can select up to 100 groups per column.
No. On a locked row the description control is hidden, so the description cannot be opened or changed.
The comments helper writes only to columns that do not have a description yet, and it is disabled when all columns have one. The primary key helper is available until a key is defined. Both write unsaved changes into the grid, so review them and click Apply.