laravel/framework — pull request #3841 by JosephSilber (2014-03-09 18:46:47+00:00)
Title: Create a composite index for morphing columns

When creating morphing columns with `$table->morphs(...)`, we should also create a composite index with those columns.

I think this is a good default. If anyone doesn't want the index, they can fall back to creating those two columns separately.

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I pulled against master since I consider this a breaking change; re-running a migration shouldn't introduce a new index.