Mapping Indexes with Yaml in Doctrine 2

indexing_columns_doctrine2.yml

# Example. A category entity with a url friendly 'slug'
# we want to index on this slug because we will be using it 
# to query with.

Vendor\CategoryBundle\Entity\Category:
    type: entity
    table: category
    indexes:
        # the name of the index
        category_slug_idx:
            # Columns is an array, specify multiple columns for 
            # a compound index
            columns: [ slug ]
    id:
        id:
            type: integer
            generator: { strategy: AUTO }

    fields:
        name:
            type: string
        slug:
            type: string

join_table_metadata.yml

# Example 2: a blog article with multiple image entities
# We want to add a caption for each image so we create a Join table 
# with meta data, and the primary key is a composite of the primary keys 
# from both the blog and image entity 

Vendor\BlogBundle\Entity\BlogImage:
    type: entity
    table: blog_image
    
    # use two fields for our identifier
    id:
        blog:
            # flag as an association key 
            associationKey: true
        image:
            associationKey: true
    fields:
        caption:
            type: string

    # Specify our relationships for above
    manyToOne:
        project:
            targetEntity: Vendor\BlogBundle\Entity\Blog
            inversedBy: images

    oneToOne:
        image:
            targetEntity: Vendor\ImageBundle\Entity\Image