== Server-Side Pagination ==
Currently we do all pagination client-side which won't be possible to keep doing as we accumulate more data

This will be needed for:
 * [wiki:HaitiRMSToDo Request Management System]
 * [wiki:HaitiOrgsToDo Organisation Registry]
 * [wiki:HaitiVolToDo Volunteer Registry]

fractalis has offered to look at this

=== Status ===
 * The Back-end is now done for HTML representation
 * The Back-end was already done for JSON representation
 * The Front-end still needs doing

=== Front-end implementation ===
 * http://datatables.net/examples/data_sources/server_side.html
 * We'll also need to hand-off the Searching & Sorting!

Client-side, we need to add these options to {{{views/dataTables.html}}} [make them Optional per-REST Controller?]:
{{{
    "bProcessing": true,
    "bServerSide": true,
    "sAjaxSource": "{{=URL(r=request, c='module', r='resource', vars={'...':'...'})}}"
}}}

Server-side, we need to understand these vars:
{{{
# Pagination
iDisplayStart - maps to 'start'
iDisplayLength - maps to 'limit'
# Ordering
iSortCol_0
iSortingCols
iSortCol_x
iSortDir_x
# Filtering (Search) - across all fields!
sSearch
}}}
response should be sent in tbhis format:
{{{
aaData": [
    [row1.field1.value, row1.field2.value, row1.field3.value],
    [row2.field1.value, row2.field2.value, row2.field3.value]
]
}}}
e.g. using a function like:
{{{
def callback():
    print request.vars
    from gluon.serializers import json
    query = ....
    rows = db(query).select() #<<<
    r=dict(rEcho=1,
           iTotalRecords=len(rows),
           iTotalDisplayRecords=len(rows),
           aaData=[[row.field1,row.field2] for row in rows])
    return json(r)
}}}
If you print request.vars you can easy figure out what paramers are being passed and change the <<< line accordingly.
=== JSON Back-end implementation ===
 * Support already present in {{{modules\s3xrc.py}}}
  * {{{http://S3_PUBLIC_URL/module/resource.json?limit=x&start=y}}}
 * needs patching for dataTables-expectations:
{{{
if "start" in self.request.vars:
    start = int(self.request.vars["start"])
elif "iDisplayStart" in self.request.vars:
    # dataTables
    start = int(self.request.vars["iDisplayStart"])
else:
    start = None

if "limit" in self.request.vars:
    limit = int(self.request.vars["limit"])
elif "iDisplayLength" in self.request.vars:
    # dataTables
    limit = int(self.request.vars["iDisplayLength"])
else:
    limit = None
}}}
 * actually needs a complete new representation!
=== HTML Back-end implementation ===
Patched the {{{models\01_RESTlike_Controller}}} to support {{{http://S3_PUBLIC_URL/module/resource?limit=x&start=y}}}
{{{
shn_list()
...
     if request.vars.limit:
        limit = int(request.vars.limit)
        if request.vars.start:
            start = int(request.vars.start)
            limitby = (start, start + limit)
        else:
            limitby = (0, limit)
    else:
        limitby = None
...
items = crud.select(table, query=query,
            ...
            limitby=limitby, 
            ...
            )
}}}

=== Other Options ===
 * Maybe look at the currently-unused {{{modules/webgrid.py}}}.
 * pagenav in {{{models\01_RESTlike_Controller}}} seems unused currently...was an older implementation of a webgrid...can probably be removed.

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[wiki:Haiti]