createdAt updatedAt attributes automatically managed?

[owain68]

I have been using Single Table Design for quite a while using the Document Client. I generally append createdAt and updatedAt on all entities in the table using the Document client within a database "wrapper". Here is a code snippet.

  update: async (updateItem: DocumentClient.UpdateItemInput) => {
    console.debug('updateItem: ', JSON.stringify(updateItem, null, 2))
    const amendedUpdateItem = updateItem
    amendedUpdateItem.TableName = tableName
    amendedUpdateItem.UpdateExpression = updateItem.UpdateExpression?.toLowerCase().includes('set ')
      ? `${updateItem.UpdateExpression}, updatedAt = :updatedAt`
      : `${updateItem.UpdateExpression} SET updatedAt = :updatedAt`
    amendedUpdateItem.ExpressionAttributeValues = { ...updateItem.ExpressionAttributeValues, ...{ ':updatedAt': new Date().toISOString() } }
    amendedUpdateItem.ReturnValues = updateItem.ReturnValues || 'ALL_NEW'

Is there a way I could do this more simply in ElectroDB with attribute Getters and Setters? Would I have to do this on each Entity within the single table or could it be done in some sort of context across all entities? Rather like #471 for the security context.

[zirkelc]

You need to add the timestamps to all your entities. Here's how I do it:

import {
  Attribute,
} from 'electrodb';

export const TIMESTAMP_ATTRIBUTES = {
  createdAt: {
    type: 'string',
    readOnly: true,
    // required: true,
    default: () => DateTime.now().iso(),
    set: (value, schema) => {
      return DateTime.now().iso();
    },
  },
  updatedAt: {
    type: 'string',
    readOnly: true,
    watch: '*',
    set: (value, schema) => {
      return DateTime.now().iso();
    },
  },
} as const satisfies { [attribute: string]: Attribute };

[owain68]

@zirkelc that looks very cool. So on all of the mutations this is done automatically under the covers. So on item creation the default is populated and on the update the watch: '*' means when any attribute that is updated then the set function is triggered. Is my understanding correct?

Thanks.

[zirkelc]

Yes, that's correct. Here's a playground link where you can see it: Playground

The examples uses Date.now() but the rest is the same.