Content Management Systems - MongoDB Applied Design Patterns - page 124

Since our queries tend to use both metadata.parent_id and metadata.slug , a unique index
on this combination is sufficient to get good performance:

>>> >>> db . cms . assets . files . ensure_index ([

... ... ( 'metadata.parent_id' , 1 ), ( 'metadata.slug' , 1 )], unique = True )

Locate and render a node

To locate a “normal” node based on the value of metadata.parent_id and metadata.slug ,
we can use the find_one operation rather than find :

node = db . nodes . find_one ({ 'metadata.parent_id' : parent_id ,
'metadata.slug' : slug })

To locate an image based on the value of metadata.parent_id and metadata.slug , we use
the GridFS method get_version :

code , sourceCode , python
fs = GridFS ( db , 'cms.assets' )
with with fs . get_version ({ 'metadata.parent_id' : parent_id , 'metadata.slug' : slug })

aas img_fpo :
# do something with the image file

Search for nodes by tag

To retrieve a list of “normal” nodes based on their tags, the query is straightforward:

nodes = db . nodes . find ({ 'metadata.tags' : tag })

To retrieve a list of images based on their tags, we'll perform a search on cms.assets.files
directly:

image_file_objects = db . cms . assets . files . find ({ 'metadata.tags' : tag })
fs = GridFS ( db , 'cms.assets' )
for

for image_file_object iin db . cms . assets . files . find (
{ 'metadata.tags' : tag }):
image_file = fs . get ( image_file_object [ '_id' ])
# do something with the image file