When we allow a user to link up to a new social network, we'd like to be able to add their ID to the social_identities collection without any regard to its current contents. To do so, we use a syntax similar to that of element replacement in a list:
UPDATE "users" SET "social_identities"['instagram'] = 9839025, "social_identities"['yo'] = 25 WHERE "username" = 'alice';
It's also perfectly valid to overwrite a value at an existing key; since keys are unique, the previous value will be replaced with the given one:
UPDATE "users" SET "social_identities"['twitter'] = 2725634 WHERE "username" = 'alice';
Checking the value of the map in the alice row, we can confirm that the Twitter ID is the most recently ...
