<para><varname>raster_overviews</varname> this view catalogs all the rasters tables in your database that server as overviews for a finer grained table. Tables of this type are generated when you use the <varname>-l</varname> switch during load.</para>
</listitem>
</orderedlist>
+ <sect2 id="RT_Raster_Columns">
+ <para>The <varname>raster_columns</varname> is a catalog of all columns in the table taht are of type raster. It is a view utilizing the constraints on the tables
+ so the information is always consistent even if you restore one raster table from a backup of another database. The following columns exist in the <varname>raster_columns</varname> catalog.</para>
+ <para>If you created your tables not with the loader or forgot to specified the <varname>-C</varname> flag during load, you can enforce the constraints after the
+ fact using <xref linkend="AddRasterConstraints" /> so that the <varname>raster_columns</varname> catalog registers the common information after your raster tiles.</para>
+
+ <orderedlist>
+ <listitem>
+ <para><varname>r_table_catalog</varname> The database the table is in. This will always read the current database.</para>
+ </listitem>
+ <listitem>
+ <para><varname>r_table_schema</varname> The database schema the raster table belongs to.</para>
+ </listitem>
+ <listitem>
+ <para><varname>r_table_name</varname> raster table</para>
+ </listitem>
+ <listitem>
+ <para><varname>r_raster_column</varname> the table that is of type raster. There is nothing in PostGIS preventing you from having multiple raster columns per table so its possible to have a raster table listed multiple times with a different raster column for each.</para>
+ </listitem>
+ <listitem>
+ <para><varname>srid</varname> The spatial reference identifier of the raster. Should be an entry in the <xref linkend="spatial_ref_sys" />.</para>
+ </listitem>
+ <listitem>
+ <para><varname>scale_x</varname> The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same <varname>scale_x</varname> and this constraint is applied. Refer to <xref linkend="RT_ST_ScaleX" /> for more details.</para>
+ </listitem>
+ <listitem>
+ <para><varname>scale_y</varname> The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same <varname>scale_y</varname> and the <varname>scale_y</varname> constraint is applied. Refer to <xref linkend="RT_ST_ScaleY" /> for more details.</para>
+ </listitem>
+ <listitem>
+ <para><varname>blocksize_x</varname> The width (number of pixels across) of each raster tile . Refer to <xref linkend="RT_ST_Width" /> for more details.</para>
+ </listitem>
+ <listitem>
+ <para><varname>blocksize_y</varname> The width (number of pixels down) of each raster tile . Refer to <xref linkend="RT_ST_Height" /> for more details.</para>
+ </listitem>
+ <listitem>
+ <para><varname>same_alignment</varname> A boolean that is true if all the raster tiles have the same alignment . Refer to <xref linkend="RT_ST_SameAlignment" /> for more details.</para>
+ </listitem>
+ <listitem>
+ <para><varname>regular_blocking</varname> This is a true/false constraint flag set on the table to denote if the tiles form a complete rectangle. It is not really validated but just taken as a given.</para>
+ </listitem>
+ <listitem>
+ <para><varname>num_bands</varname> The number of bands in each tile of your raster set. This is the same information as what is provided by <xref linkend="RT_ST_NumBands" /></para>
+ </listitem>
+ <listitem>
+ <para><varname>pixel_types</varname> An array defining the pixel type for each band. You will have the same number of elements in this array as you have number of bands. The pixel_types are one of the following defined in <xref linkend="RT_ST_BandPixelType" />.</para>
+ </listitem>
+ <listitem>
+ <para><varname>nodata_values</varname> An array of double precision numbers denoting the <varname>nodata_value</varname> for each band. You will have the same number of elements in this array as you have number of bands. These numbers define the pixel value for each band that should be ignored for most operations. This is similar information provided by <xref linkend="RT_ST_BandNoDataValue" />.</para>
+ </listitem>
+ <listitem>
+ <para><varname>extent</varname> This is the extent of all the raster rows in your raster set. If you plan to load more data that will change the extent of the set, you'll want to drop the <xref linkend="RT_DropRasterConstraints" /> function before load and then reapply constraints with <xref linkend="RT_AddRasterConstraints" /> after load. </para>
+ </listitem>
+ </orderedlist>
+ </sect2>
</sect1>
</chapter>
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