Following on from my related prior question, let me elaborate this topic a bit.
raster2pgsql is a raster loader executable that loads GDAL supported raster formats in PostGIS. It has a
-C flag defined as follows:
-C Set the standard set of constraints on the raster column after the rasters are loaded. Some constraints may fail if one or more rasters violate the constraint.
When I am importing my raster file like this:
gislinux@gislinux-Precision-M4600:~$ raster2pgsql -d -I -C -M -F -t 100x100 -s 4326 us_tmin_2012.01.asc chp05.us_tmin_new | psql -h localhost -p 5432 -U postgres -d pgrouting
ANALYZE NOTICE: Adding SRID constraint CONTEXT: PL/pgSQL function addrasterconstraints line 53 at RETURN NOTICE: Adding scale-X constraint
Few constraints have been applied to this new table by the
pgrouting=# \d+ chp05.us_tmin_new
Indexes: "us_tmin_new_pkey" PRIMARY KEY, btree (rid) "us_tmin_new_rast_gist" gist (st_convexhull(rast)) Check constraints: "enforce_height_rast" CHECK (st_height(rast) = ANY (ARRAY[100, 21])) "enforce_max_extent_rast" CHECK (st_coveredby(st_convexhull(rast),
The standard constraints comprise the following rules (although these constraints are acting independently on all the incoming raster tiles):
- Width and height: This rule states that all the rasters must have the same width and height.
- Scale X and Y: This rule states that all the rasters must have the same scale X and Y.
- SRID: This rule states that all rasters must have the same SRID.
- Same alignment: This rule states that all rasters must be aligned to one another.
- Maximum extent: This rule states that all rasters must be within the table's maximum extent.
- Number of bands: This rule states that all rasters must have the same number of bands (means this ensures that all the coming rasters must have a specific number of bands, it's not comparing existing raster tiles).
- NODATA values: This rule states that all raster bands at a specific index must have the same NODATA value.
- Out-db: This rule states that all raster bands at a specific index must be in-db or out-db, not both.
- Pixel type: This rule states that all raster bands at a specific index must be of the same pixel type.
NOW, in order to run
ST_MapAlgebra function, I had to drop these std constraints individually, which I did using:
ALTER TABLE chp05.us_tmin_new DROP CONSTRAINT enforce_scalex_rast
in pgAdmin SQL Editor for each of those std constraints. But now I don't know how to bring these standard constraints back? The following command is not working:
ALTER TABLE chp05.us_tmin_new ADD CONSTRAINT enforce_scalex_rast unique (rast);
and giving the following error:
ERROR: data type raster has no default operator class for access method "btree" HINT: You must specify an operator class for the index or define a default operator class for the data type.