| 531 | | PostGIS is using the typmod feature of PostgreSQL to 'store' metadata about a table and then display them in the geometry_column view. Unfortunately the typmod is limited to XXX byte and there is too much information to 'store' about a raster table to use typmod. PostGIS raster will therefore use another technique to 'store' metadata about a raster table: constraint. A set of constraint will be applied to a raster table and those constraint will be read and displyed by the raster_column view. |
| | 531 | PostGIS is using the typmod feature of PostgreSQL to 'store' metadata about a table and then display them in the geometry_column view. Unfortunately the typmod is limited to XXX byte and there is too much information to 'store' about a raster table to use typmod. PostGIS raster will therefore use another approch consisting in 'store' metadata about a raster table as constraint on the table. A set of constraint will be applied to a raster table and those constraint will be read and displayed by the raster_column view. |
| | 532 | |
| | 533 | The major changes concerning the raster_column table are as follow: |
| | 534 | |
| | 535 | * There will be a flexible ApplyRasterConstraint() function trying to apply a set of constraint on a table. As for any constraint, the constraints will be successfully applied only when all the rows of the table fulfil the constraint. |
| | 536 | |
| | 537 | * This function will be called by the new C raster2pgsql C loader. |
| | 538 | |
| | 539 | * The raster_column view rows will be determined by querying the PostgreSQL catalog. A typical query exist for this. |
| | 540 | |
| | 541 | * The raster_column will derive columns of metadata from the constraints applied to each table listed. When a constraint could not be applied successfully to the table, the column for this table will be null. |
| | 542 | |
| | 543 | The major changes concerning the raster_column table are as follow: |
| | 544 | |
| | 545 | * We will provide two functions to support the creation of the raster_overview view and application of two additional constraints specific to overviews (ApplyOverviewConstraints) and a function for creating overviews (ST_CreateOverview()). |
| | 546 | |
| | 547 | * The raster_overview table will NOT be created by default by the rtpostgis.sql script. It will be up to applications to use the ApplyOverviewConstraints and ST_CreateOverview() function to enable overviews support. |
| | 548 | |
| | 549 | The major changes concerning the raster2pgsql loader are as follow: |
| | 550 | |
| | 551 | * We are working on a new C importer to get rid of any Python, Numpy and Python GDAL binding dependency. |
| | 552 | * This new importer will NOT have any option to create the raster_overview view, nor to create overview tables. We think that it is more important to be able to create overview in SQL as a post process query so overviews can be updated/recreated when rasters tiles are edited, added or deleted. |
| | 553 | * We will stop supporting the old raster2pgsql.py which was creating overview tables and filling the raster_overview table. It will be available in the script/python folder for people wishing to create overviews after a slight modification. |
| | 554 | |
| | 555 | |
| | 556 | '''More Details''' |
