[From Postgres to Mongo] : Added temp collections to lower data unavailability time

[antoineludeau]

Context

Currently, when transfering data from main db (postgresql) to our exploitation db (mongodb), we are, in this order, :

• deleting old data from mongo
• creating temp sql tables with code postal calculation
• then, page per page (page = 100 items) we are :
  • getting data
  • formating data
  • inserting data into mongo

This can take a long time to processing especially for big cities like 'Toulouse' for example (around 15 minutes). As a consequence, the data in our exploitation db, that has been deleted at the beginning, is unavailable during that processing time.

Enhancement

To solve this issue, this PRs adds a mechanism of "temp collection" :

• all the processed data will be inserted in those temp collection (temp_voies_${cog} and temp_numero_${cog})
• when all the data is inserted, the old data is deleted and replaced by the data from those temp collections
• the temp collections are deleted