[wiki:Haiti]
== 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]

=== Status ===
 * The Back-end is now done for HTML representation
 * The Back-end was already done for JSON representation, now done in the dataTables way
 * The Front-end is done: 50 records at a time :)
 * !ToDo:
  * ~~Push from Dev to Live~~
  * ~~Render as .represent~~
  * ~~Render the ID as View/Edit button depending on perms~~
   *  ~~Done via a .represent for RMS~~
  * ~~Return RMS to Live (1 line in Controller functions: response.s3.pagination = True)~~
  * Handle Component Views (use list_fields instead of all readable)
  * ~~Sort Columns (orderby)~~ need to enhance sorting for reference columns: it is expected to be alphabetic, and now it is per foreign ids
  * ~~Search (filtering)~~ need to include reference columns (lookup tables at least) which are being ignored currently 
  * XSLT to generate dataTables-compliant JSON? (update: was not needed for the current functionality)
=== Front-end implementation ===
 * http://datatables.net/examples/data_sources/server_side.html
 * http://datatables.net/usage/server-side
 * 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 <<<<--------- now sSortDir_x since jquery.dataTables.fixed.js 1.6.1 
                         need to watch out for the future upgrades compatibility!
                         
# Filtering (Search) - across all fields!
sSearch
}}}
response should be sent in this format:
{{{
{
"sEcho": 1,
"aaData": [
    [row1.id, row1.field2, ...],
    [row2.id, row2.field2, ...],
    [row3.id, row3.field2, ...]
],
"iTotalRecords": 3,
"iTotalDisplayRecords": 3
}
}}}
e.g. using a function like (although we've integarted into {{{models/01_RESTlike_controller.py}}}):
{{{
def callback():
    iDisplayStart = int(request.vars.iDisplayStart)
    iDisplayLength = int(request.vars.iDisplayLength)
    from gluon.serializers import json
    _table = '%s_%s' % (request.controller, request.function)
    table = db[_table]
    query = (table.id > 0)
    rows = db(query).select(limitby = (iDisplayStart, iDisplayStart + iDisplayLength))
    r = dict(sEcho = 1,
           iTotalRecords = len(rows),
           iTotalDisplayRecords = len(rows),
           aaData = [[row[f] for f in table.fields if table[f].readable] for row in rows])
    return json(r)
}}}

Problems:
 * ~~http://datatables.net/forums/comments.php?DiscussionID=1156&page=1#Item_1~~
 * ~~No .represent rendered~~
 * ~~Represent doesn't handle ID, so can't pledge Aid for Requests in RMS (or see record details in OR)~~
 * ~~Represent doesn't handle the marker_id, so gis_location has the big image for each marker visible~~

=== 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 unless this could be done via XSLT!?
  * still needs extension adding to shn_xml_export_formats in {{{models\01_RESTlike_controller.py}}} 
=== 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 ===
 * ExtJS
 * Maybe look at the currently-unused {{{modules/webgrid.py}}}: http://www.web2pyslices.com/main/slices/take_slice/39
  * pagenav in {{{models\01_RESTlike_Controller}}} was an older implementation of a webgrid...has been removed.

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[wiki:Haiti]