PG raster: support mosaics with no metadata

Fixes #39017

src/providers/postgres/raster/qgspostgresrasterprovider.cpp

@@ -1221,10 +1221,7 @@ bool QgsPostgresRasterProvider::init()
     where = QStringLiteral( "WHERE %1" ).arg( subsetString() );
   }
 
-  // If we dropped here from the fast track because there was something wrong reading metadata
-  // we can safely assume that the raster is NOT tiled and add LIMIT 1 in the query below to
-  // speed things up.
-
+  // Unfortunately we cannot safely assume that the raster is untiled and just LIMIT 1
   // Fastest SQL: fetch all metadata in one pass
   //   0           1          3           3        4       5         6       7       8       9      10          11           12           13      14
   // encode | upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands | pixeltype | nodatavalue | isoutdb | path
@@ -1237,9 +1234,7 @@ bool QgsPostgresRasterProvider::init()
                         (ST_Metadata( band  )).*,
                         (ST_BandMetadata( band )).*
                       FROM cte_band
-  )" ).arg( quotedIdentifier( mRasterColumn ),
-                                          tableToQuery,
-                                          where.isEmpty() &&mUseEstimatedMetadata ? QStringLiteral( "LIMIT 1" ) : where ) };
+  )" ).arg( quotedIdentifier( mRasterColumn ), tableToQuery, where ) };
 
   QgsDebugMsgLevel( QStringLiteral( "Raster information sql: %1" ).arg( sql ), 4 );
 

tests/src/python/test_provider_postgresraster.py

@@ -80,6 +80,7 @@ class TestPyQgsPostgresRasterProvider(unittest.TestCase):
         cls._load_test_table(
             'public', 'int16_regression_36689', 'bug_36689_pg_raster')
         cls._load_test_table('public', 'bug_37968_dem_linear_cdn_extract')
+        cls._load_test_table('public', 'bug_39017_untiled_no_metadata')
 
         # Fix timing issues in backend
         # time.sleep(1)
@@ -493,8 +494,8 @@ class TestPyQgsPostgresRasterProvider(unittest.TestCase):
                 table='bug_37968_dem_linear_cdn_extract', schema='public'), 'pg_layer', 'postgresraster')
 
         self.assertTrue(rl.isValid())
-        compareWkt(rl.extent().asWktPolygon(
-        ), 'POLYGON((-40953.223387096 170588, -40873.21532258 170588, -40873.21532258 170668, -40953.223387096 170668, -40953.23387096))')
+        self.assertTrue(compareWkt(rl.extent().asWktPolygon(
+        ), 'POLYGON((-40953 170588, -40873 170588, -40873 170668, -40953 170668, -40953 170588))', 1))
         block = rl.dataProvider().block(1, rl.extent(), 6, 6)
         data = []
         for i in range(6):
@@ -503,6 +504,57 @@ class TestPyQgsPostgresRasterProvider(unittest.TestCase):
 
         self.assertEqual(data, [52, 52, 52, 52, 44, 43, 52, 52, 52, 48, 44, 44, 49, 52, 49, 44, 44, 44, 43, 47, 46, 44, 44, 44, 42, 42, 43, 44, 44, 48, 42, 43, 43, 44, 44, 47])
 
+    def testUntiledMosaicNoMetadata(self):
+        """Test regression https://github.com/qgis/QGIS/issues/39017
+
+            +-----------+------------------------------+
+            |           |                              |
+            |  rid = 1  |          rid = 2             |
+            |           |                              |
+            +-----------+------------------------------+
+
+        """
+
+        rl = QgsRasterLayer(
+            self.dbconn + " sslmode=disable table={table} schema={schema}".format(
+                table='bug_39017_untiled_no_metadata', schema='public'), 'pg_layer', 'postgresraster')
+        self.assertTrue(rl.isValid())
+        self.assertTrue(compareWkt(rl.extent().asWktPolygon(
+        ), 'POLYGON((47.061 40.976, 47.123 40.976, 47.123 41.000, 47.061 41.000, 47.061 40.976))', 0.01))
+
+        rl1 = QgsRasterLayer(
+            self.dbconn + " sslmode=disable table={table} schema={schema} sql=\"rid\"=1".format(
+                table='bug_39017_untiled_no_metadata', schema='public'), 'pg_layer', 'postgresraster')
+        self.assertTrue(rl1.isValid())
+        self.assertTrue(compareWkt(rl1.extent().asWktPolygon(
+        ), 'POLYGON((47.061 40.976, 47.070 40.976, 47.070 41.000, 47.061 41.000, 47.061 40.976))', 0.01))
+
+        rl2 = QgsRasterLayer(
+            self.dbconn + " sslmode=disable table={table} schema={schema} sql=\"rid\"=2".format(
+                table='bug_39017_untiled_no_metadata', schema='public'), 'pg_layer', 'postgresraster')
+        self.assertTrue(rl2.isValid())
+        self.assertTrue(compareWkt(rl2.extent().asWktPolygon(
+        ), 'POLYGON((47.061 40.976, 47.123 40.976, 47.123 41.000, 47.070 41.000, 47.070 40.976))', 0.01))
+
+        extent_1 = rl1.extent()
+        extent_2 = rl2.extent()
+
+        def _6x6_block_data(layer, extent):
+            block = layer.dataProvider().block(1, extent, 6, 6)
+            data = []
+            for i in range(6):
+                for j in range(6):
+                    data.append(int(block.value(i, j)))
+            return data
+
+        rl_r1 = _6x6_block_data(rl, extent_1)
+        r1_r1 = _6x6_block_data(rl1, extent_1)
+        self.assertEqual(rl_r1, r1_r1)
+
+        rl_r2 = _6x6_block_data(rl, extent_2)
+        r2_r2 = _6x6_block_data(rl2, extent_2)
+        self.assertEqual(rl_r2, r2_r2)
+
 
 if __name__ == '__main__':
     unittest.main()