I'm pretty new to couchDB and even after reading (latest archive as now deleted) http://wiki.apache.org/couchdb/How_to_store_hierarchical_data (via ‘Store the full path to each node as an attribute in that node's document’) it's still not clicking just yet.
Instead of using the full path pattern as described in the wiki I'm hoping to keep track of children as an array of UUIDs and the parent as a single UUID. I'm leaning towards this pattern so I can maintain the order of children by their positions in the children array.
Here are some sample documents in couch, buckets can contain buckets and items, items can only contain other items. (UUIDs abbreviated for clarity):
{_id: 3944
name: "top level bucket with two items"
type: "bucket",
parent: null
children: [8989, 4839]
}
{_id: 8989
name: "second level item with no sub items"
type: "item"
parent: 3944
}
{
_id: 4839
name: "second level bucket with one item"
type: "bucket",
parent: 3944
children: [5694]
}
{
_id: 5694
name: "third level item (has one sub item)"
type: "item",
parent: 4839,
children: [5390]
}
{
_id: 5390
name: "fourth level item"
type: "item"
parent: 5694
}
Is it possible to look up a document by an embedded document id within a map function?
function(doc) {
if(doc.type == "bucket" || doc.type == "item")
emit(doc, null); // still working on my key value output structure
if(doc.children) {
for(var i in doc.children) {
// can i look up a document here using ids from the children array?
doc.children[i]; // psuedo code
emit(); // the retrieved document would be emitted here
}
}
}
}
In an ideal world final JSON output would look something like.
{"_id":3944,
"name":"top level bucket with two items",
"type":"bucket",
"parent":"",
"children":[
{"_id":8989, "name":"second level item with no sub items", "type":"item", "parent":3944},
{"_id": 4839, "name":"second level bucket with one item", "type":"bucket", "parent":3944, "children":[
{"_id":5694", "name":"third level item (has one sub item)", "type":"item", "parent": 4839, "children":[
{"_id":5390, "name":"fourth level item", "type":"item", "parent":5694}
]}
]}
]
}