AddOverviewConstraints
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## Name

AddOverviewConstraints — Tag a raster column as being an overview of another.

## Synopsis

`boolean AddOverviewConstraints(`name ovschema, name ovtable, name ovcolumn, name refschema, name reftable, name refcolumn, int ovfactor`)`;

`boolean AddOverviewConstraints(`name ovtable, name ovcolumn, name reftable, name refcolumn, int ovfactor`)`;

## Description

Adds constraints on a raster column that are used to display information in the `raster_overviews` raster catalog.

The `ovfactor` parameter represents the scale multiplier in the overview column: higher overview factors have lower resolution.

When the `ovschema` and `refschema` parameters are omitted, the first table found scanning the `search_path` will be used.

Availability: 2.0.0

## Examples

    CREATE TABLE res1 AS SELECT
    ST_AddBand(
      ST_MakeEmptyRaster(1000, 1000, 0, 0, 2),
      1, '8BSI'::text, -129, NULL
    ) r1;

    CREATE TABLE res2 AS SELECT
    ST_AddBand(
      ST_MakeEmptyRaster(500, 500, 0, 0, 4),
      1, '8BSI'::text, -129, NULL
    ) r2;

    SELECT AddOverviewConstraints('res2', 'r2', 'res1', 'r1', 2);

    -- verify if registered correctly in the raster_overviews view --
    SELECT o_table_name ot, o_raster_column oc,
           r_table_name rt, r_raster_column rc,
           overview_factor f
    FROM raster_overviews WHERE o_table_name = 'res2';
      ot  | oc |  rt  | rc | f
    ------+----+------+----+---
     res2 | r2 | res1 | r1 | 2
    (1 row)

## See Also

Section 11.2.2, “Raster Overviews”, DropOverviewConstraints, ST_CreateOverview, AddRasterConstraints

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