"Table scan" CouchDB map-reduce.

gistfile1.js

/**
 * Run a chained map reduce on a couchdb view
 * 
 * @param db The db to use
 * @param view The view name
 * @param map_func The map function to use on the view results function({ key: , value: }) -> { key: , value: }
 * @param config Standard jquery.couch.js config options
 */
var chainCouch = (function() {
	
var cmp,
	icmp;

cmp = function(keya, keyb) {
	var ret = 0;
	
	if (Array.isArray(keya)) {
		$.each(keya, function(i, va) {
			var vb = keyb[i];
			ret = cmp(va, vb);
			if (ret !== 0) {
				return false;
			}
		});
		if ((ret === 0) && (keya.length < keyb.length)) {
			return -1;
		}
		return ret;
	}
	
	if (typeof(keya) == 'object') {
		if (typeof(keyb) == 'object') {
			return 0;
		}
		return 1;
	}
	if (typeof(keyb) == 'object') {
		return -1;
	}
	
	if (keya < keyb) {
		return -1;
	}
	if (keya > keyb) {
		return 1;
	}
	return 0;
}

icmp = function(keya, keyb) {
	return -cmp(keya, keyb);
}

return function(db, view, map_func, config) {
	var startkey = config.startkey,
		endkey = config.endkey,
		is_reverse = config.descending,
		c = cmp,
		limit = config.limit;
	
	if (is_reverse) {
		c = icmp;
	}
	
	db.view(view, {
		reduce: true,
		group: true,
		success: function(result) {
			var mapped = $.map(result.rows, map_func),
				sort_func;
	
			// slice
			mapped = $.map(mapped, function(row) {
				var key = row.key;
				
				if (c(startkey, key) > 0) {
					return;
				}
				if (c(endkey, key) < 0) {
					return;
				}
				
				return row;
			});
			
			mapped.sort(function(rowa, rowb) {
				return c(rowa.key, rowb.key);
			});
			
			if (limit) {
				mapped = mapped.slice(0, limit);
			}
			config.success({ rows: mapped });
		}
	});
};
}());