Changes between Version 41 and Version 42 of WKTRaster/GDALDriverSpecificationWorking

Timestamp:

09/14/11 10:51:05 (14 years ago)

Author:

jorgearevalo

Comment:

Question responded

WKTRaster/GDALDriverSpecificationWorking

@@ -146 +146 @@
 So, basically the psc for IRasterIO is right, but as GDAL is prepared for a blocked I/O with same size blocks and PostGIS Raster can't ensure all the coverage tiles have the same size, we must take a decission:
   * Get rid of the GDAL block concept and simply get all the requested data in a query from IRasterIO method. That implies getting rid of GDAL block cache too.
-  * Adapt our ''messy'' arrangement to GDAL block system, by dividing the data fetched from database in equally sized blocks, and manually adding them to the cache. An important thing here is what happens when some raster data, stored in the cache, is modified. Using the GDAL cache system, you can simply replace the data in the cache and mark the block as ''dirty'' (using GDALRasterBlock::MarkDirty method), but... '''Q: Are the dirty blocks written to disk (database, in our case) by IWriteBlock method? If not, how?'''
+  * Adapt our ''messy'' arrangement to GDAL block system, by dividing the data fetched from database in equally sized blocks, and manually adding them to the cache. An important thing here is what happens when some raster data, stored in the cache, is modified. Using the GDAL cache system, you can simply replace the data in the cache and mark the block as ''dirty'' (using GDALRasterBlock::MarkDirty method), but... '''Q: Are the dirty blocks written to disk (database, in our case) by IWriteBlock method? If not, how?''' '''Response (jorgearevalo): Yes, IWriteBlock persists the blocks to database'''
 
 After a conversation between Pierre Racine and Jorge Arevalo, we agree on the approach of getting all data in IRasterIO, dividing it into equally sized blocks and storing them in the cache. Jorge Arevalo is working on it (September 2011).