Link tables

It’s useful to keep track of the link between a Source record and a Target record in a so called “Link table”. Benefits of a link table:

It’s a log of all records that have been successfully synced to the target
It can be used to lookup the id in the target of a parent record, when adding a child
It can be used for rollback (delete records in target)

This table can be created manually in Peliqan for each object type in the sync, and the table contains at minimum 2 columns:

source_id
target_id

Example link table for “Task” objects: Table name: link_table_tasks

source_id	target_id
1	abc456
6	def789
8	ghi432

Pseudo-code:

GET SOURCE ROWS

FOR EACH SOURCE ROW:

		CHECK IF RECORD ALREADY IN TARGET (LOOKUP IN LINK TABLE) ? IF NOT:
					
			1. DO FIELD MAPPING
			
			2. ADD TO TARGET
			
			3. ADD ROW IN "LINK TABLE"

Here’s the pseudo code in a bit more detail for records of type “Task”:

source_rows = dw.fetch(table)    	               # e.g. list of "Tasks"

for row in source_rows:

		source_id = row["task_id"]
		if source_id not in link_table_tasks:       # Task is not in target yet
		  
				# Field mapping
				target_row = {
					target_field = source_field,
					target_field = source_field,
					target_field = source_field
				}
				
				target_id = target.add(target_row)
				dw.insert("link_table_tasks", source_id, target_id)

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