> For the complete documentation index, see [llms.txt](https://docs.syntho.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.syntho.ai/configure-a-data-generation-job/configure-column-settings/key-generators.md).
# Key generators
Key generators control how primary key (PK) and foreign key (FK) values appear in generated data. They preserve referential integrity between related tables.
Choose **Duplicate**, **Generate**, or **Hash** based on whether you must preserve source values or relationships.
Choose a key generator based on how you need to handle key values and relationships.
| Generator | Description | When to use | When not to use |
| --------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Duplicate | Copies the original key values exactly as they appear in the source data, preserving both the correlations and referential integrity between primary and foreign keys. | When it’s essential to maintain the original key values and relationships, particularly in de-identification scenarios where the data structure must be preserved without generating new keys. | Upsampling is not supported when using Duplicate, as the original keys are simply copied, not expanded. Additionally, it is not recommended when the keys are sensitive and need to be protected, as this method retains the original key values without obfuscation. |
| Generate | Creates new, synthetic key values that do not correspond to the original keys. It preserves only the referential integrity, but not the correlations between key columns. | Use Generate for upsampling or creating synthetic datasets where there is no need to maintain relationships with the original data. It can also be used when creating data from scratch. | The Generate function creates new keys independently of the original key order, which disrupts correlations. As a result, it is unsuitable for scenarios where maintaining the correlations and order is essential. |
| Hash | Converts original key values into hashed representations. Both correlations between tables and relational integrity are maintained. | Use Hash when you need to obscure the original key values, while ensuring correlations and referential integrity are preserved. | Upsampling, or situations where the original key values must be maintained for direct referencing, such as cases where exact key values are essential for business logic (e.g. country codes) or traceability in audit scenarios. |
## Apply key generators
### Apply a generator to a key column
{% hint style="info" %}
Applying a key generator to any key column applies the same generator settings to all linked key columns. This preserves referential integrity.
{% endhint %}
1. Open **Column settings > Generator**.
2. Select **Duplicate**, **Generate**, or **Hash**.
3. Confirm the change.
Apply a key generator to a column.
### Set the workspace default
{% hint style="info" %}
Column-level settings override the workspace default. For example, a column set to **Duplicate** overrides a workspace default of **Hash**.
{% endhint %}
1. Open **Edit workspace** from the **Saved workspaces** or **Configuration** panel.
2. Select **Default settings**.
3. Set the key generator to **Duplicate**, **Generate**, or **Hash**.
You can also use `CTRL + SHIFT + ALT + 0` to open **Workspace settings**. The selected generator applies to every key column without an override.
### Composite keys
Set the generator on any composite key column. Syntho applies it to every column in that composite key.
### Examples
The example below shows two composite keys. Each composite key uses one generator across its linked columns.
Composite key columns: Birthdate and First.
Composite key columns: Birthdate and Birthplace.
## Limitations
* **Generate** does not support composite foreign keys or columns referencing a composite key.
* Key generators do not apply to tables in **Exclude** mode.
* The same input produces the same output to preserve PK and FK links.
* Images and large binary objects do not support key generation.
---
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