MapGuide RFC 112 - sqlite based tile cache

This page contains a change request (RFC) for the MapGuide Open Source project. More MapGuide RFCs can be found on the RFCs page.

Status

RFC Template Version	(1.0)
Submission Date	(Date / Time submitted)
Last Modified	(your name here) (modification date here)
Author	Zac Spitzer
RFC Status	(draft)
Implementation Status	(pending)
Proposed Milestone	(2.3)
Assigned PSC guide(s)	(when determined)
Voting History	(vote date)

Overview

This is a proposal to implement a secondary tile cache persistance layer using a sqlite db.

Motivation

The file base tile cache can be problematic for backup or copying due to the massive number of files and directories.

A single sqlite db file per scale level, per tile cache solves this problem.

Generating tiles is currently done using a rather brute force approach, by storing
tiles in a database, it can be queried for existing tiles and only missing tiles
can be requested.

Using a sqlite database will use less disk space than a disk based tile cache.

Proposed Solution

Implement sqlite based persistance as an option for the tile cache.

Utilize FDO as the storage interface, perhaps using GDAL RasterLite ​http://www.gdal.org/frmt_rasterlite.html

Add additional API methods to the tile service to query and manage the tile cache (TBD)

Some way to convert between tile cache formats (standalone util?)

Each tile would be stored with it's extents/scale, allowing the coverage a tile cache could be visually mapped.

Implications

TBD

Test Plan

Existing Tile Cache unit tests still apply

Funding / Resources

Ennoble Community(?)