Does the order of index_together matter in a Django model?

Question

When defining a model with an index_together Meta property, does the order of the columns matter?

In other words, is there a difference between

Class myModel(models.Model):
    name = models.CharField(max_length=100)
    address = models.CharField(max_length=100)
    favorite_color = models.CharField(max_length=20)

    class Meta:
        index_together = ('name', 'address', 'favorite_color')

vs

Class myModel(models.Model):
    name = models.CharField(max_length=100)
    address = models.CharField(max_length=100)
    favorite_color = models.CharField(max_length=20)

    class Meta:
        index_together = ('favorite_color', 'name', 'address')

I only ask because I've noticed when looking at the structure of a table, each column in the key has an "index in key" property. Does MySQL/PostgreSQL expect the columns to be queried in that order?

Just as an aside, is there a great deal of difference between indexing the columns together vs separately?

Answer 1

The order of index_together explains the "path" the index is created. You can query from left to the right to profit from the index.

So with your first index_together:

    index_together = ('name', 'address', 'favorite_color')

if your first filter is name the index is used. If the first is name and the second is address the index is used, too.

But if you filter by address and then name or address, favorite_color the index can't be used.