[postgis-devel] [PostGIS] #593: [raster] Add a ST_BandIsNoData function

[PostGIS]

#593: [raster] Add a ST_BandIsNoData function
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  Reporter:  pracine         |       Owner:  jorgearevalo 
      Type:  task            |      Status:  closed       
  Priority:  medium          |   Milestone:  PostGIS 2.0.0
 Component:  postgis raster  |     Version:  trunk        
Resolution:  fixed           |    Keywords:               
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Comment(by pracine):

 Actually, tell me if I'm wrong, your change in raster2pgsql.py do not
 change anything in the database. To actually change the raster permanently
 you must do an UPDATE.

 And still it is not wise to load the raster and then UPDATE it.
 raster2pgsql.py should check the pixel values while loading them and set
 the flag properly BEFORE writing the INSERT statement. (I don't know if
 this is possible right now because the flag has to be set so early).

 Doing a full check of one table to reset the flag if needed is also
 problematic since ST_BandIsNoData just return TRUE or FALSE, not the
 updated raster with the flag correctly set. I guess we will need a
 ST_SetBandIsNoData returning a raster so we can do:

 UPDATE rastertable SET rast = ST_SetBandIsNodata(rast, 2) WHERE
 ST_BandIsNodata(rast, 2) != ST_BandIsNodata(rast, 2, TRUE);

 to update a complete table. (Any better way?)

 Anyway this ST_BandIsNoData is not a big optimization and should be low
 priority in comparison with the the other things needed for MapAlgebra. I
 would maybe just deactivate it until we have all the functions to synch it
 better with all the other edit functions. Sorry if this wasn't clear
 enough.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/593#comment:18>
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