OGR_PG_SKIP_CONFLICTS: optionally insert with ON CONFLICT DO NOTHING

autotest/ogr/ogr_pg.py

@@ -6067,3 +6067,57 @@ def test_ogr_pg_no_postgis_GEOMETRY_NAME(pg_ds):
             gdal.GetLastErrorMsg()
             == "GEOMETRY_NAME=foo ignored, and set instead to 'wkb_geometry' as it is the only geometry column name recognized for non-PostGIS enabled databases."
         )
+
+
+###############################################################################
+# Test ignored conflicts
+
+
+@only_without_postgis
+def test_ogr_pg_skip_conflicts(pg_ds):
+    pg_ds.ExecuteSQL(
+        "CREATE TABLE test_ogr_skip_conflicts(id SERIAL PRIMARY KEY, gml_id character(16), beginnt character(20), UNIQUE(gml_id, beginnt))"
+    )
+
+    with gdal.config_option("OGR_PG_SKIP_CONFLICTS", "YES"):
+        # OGR_PG_SKIP_CONFLICTS and OGR_PG_RETRIEVE_FID cannot be used at the same time
+        with gdal.config_option("OGR_PG_RETRIEVE_FID", "YES"):
+            pg_ds = reconnect(pg_ds, update=1)
+            lyr = pg_ds.GetLayerByName("test_ogr_skip_conflicts")
+            feat = ogr.Feature(lyr.GetLayerDefn())
+            feat["gml_id"] = "DERPLP0300000cG3"
+            feat["beginnt"] = "2020-07-10T04:48:14Z"
+            with gdal.quiet_errors():
+                assert lyr.CreateFeature(feat) != ogr.OGRERR_NONE
+
+    with gdal.config_option("OGR_PG_RETRIEVE_FID", "NO"):
+        pg_ds = reconnect(pg_ds, update=1)
+        lyr = pg_ds.GetLayerByName("test_ogr_skip_conflicts")
+
+        assert lyr.GetFeatureCount() == 0
+
+        feat = ogr.Feature(lyr.GetLayerDefn())
+        feat["gml_id"] = "DERPLP0300000cG3"
+        feat["beginnt"] = "2020-07-10T04:48:14Z"
+        assert lyr.CreateFeature(feat) == ogr.OGRERR_NONE
+        assert lyr.GetFeatureCount() == 1
+
+        # Insert w/o OGR_PG_SKIP_CONFLICTS=YES succeeds, but doesn't add a feature
+        with gdal.config_option("OGR_PG_SKIP_CONFLICTS", "YES"):
+            pg_ds = reconnect(pg_ds, update=1)
+            lyr = pg_ds.GetLayerByName("test_ogr_skip_conflicts")
+
+            assert lyr.GetFeatureCount() == 1
+
+            feat = ogr.Feature(lyr.GetLayerDefn())
+            feat["gml_id"] = "DERPLP0300000cG3"
+            feat["beginnt"] = "2020-07-10T04:48:14Z"
+            assert lyr.CreateFeature(feat) == ogr.OGRERR_NONE
+            assert lyr.GetFeatureCount() == 1
+
+        # Other feature succeeds and increments the feature count
+        feat = ogr.Feature(lyr.GetLayerDefn())
+        feat["gml_id"] = "DERPLP0300000cG4"
+        feat["beginnt"] = "2020-07-10T04:48:14Z"
+        assert lyr.CreateFeature(feat) == ogr.OGRERR_NONE
+        assert lyr.GetFeatureCount() == 2

doc/source/drivers/vector/nas.rst

@@ -45,6 +45,10 @@ population - which was default in ALKIS-Import. The information found there was
 redundant to the relation fields also contained in original elements/tables.
 Enabling the option also made progress reporting available.
 
+Duplicate data in datasets will usually causes errors.  When importing separate
+datasets into PostgreSQL it is useful to enable "OGR_PG_SKIP_CONFLICTS" to skip
+conflicting features.
+
 This driver was implemented within the context of the `PostNAS
 project <http://trac.wheregroup.com/PostNAS>`__, which has more
 information on its use and other related projects.

doc/source/drivers/vector/pg.rst

@@ -464,6 +464,16 @@ The following configuration options are available:
       create) the ``ogr_system_tables.metadata`` table to retrieve and store
       layer metadata.
 
+-  .. config:: OGR_PG_SKIP_CONFLICTS
+      :choices: YES, NO
+      :default: NO
+
+      If set to "YES" (not the default),
+      conflicts when inserting features will be skipped
+      (requires OGR_PG_RETRIEVE_FID to be off and only applies when PG_USE_COPY
+      is off).
+
+
 Examples
 ~~~~~~~~
 

ogr/ogrsf_frmts/pg/ogr_pg.h

@@ -339,6 +339,7 @@ class OGRPGTableLayer final : public OGRPGLayer
     void CheckGeomTypeCompatibility(int iGeomField, OGRGeometry *poGeom);
 
     int bRetrieveFID = true;
+    int bSkipConflicts = false;
     int bHasWarnedAlreadySetFID = false;
 
     char **papszOverrideColumnTypes = nullptr;

ogr/ogrsf_frmts/pg/ogrpgtablelayer.cpp

@@ -172,7 +172,9 @@ OGRPGTableLayer::OGRPGTableLayer(OGRPGDataSource *poDSIn,
       // Just in provision for people yelling about broken backward
       // compatibility.
       bRetrieveFID(
-          CPLTestBool(CPLGetConfigOption("OGR_PG_RETRIEVE_FID", "TRUE")))
+          CPLTestBool(CPLGetConfigOption("OGR_PG_RETRIEVE_FID", "TRUE"))),
+      bSkipConflicts(
+          CPLTestBool(CPLGetConfigOption("OGR_PG_SKIP_CONFLICTS", "FALSE")))
 {
     poDS = poDSIn;
     pszQueryStatement = nullptr;
@@ -2069,10 +2071,19 @@ OGRErr OGRPGTableLayer::CreateFeatureViaInsert(OGRFeature *poFeature)
     if (bRetrieveFID && pszFIDColumn != nullptr &&
         poFeature->GetFID() == OGRNullFID)
     {
+        if (bSkipConflicts)
+        {
+            CPLError(CE_Failure, CPLE_AppDefined,
+                     "fid retrieval and skipping conflicts are not supported "
+                     "at the same time.");
+            return OGRERR_FAILURE;
+        }
         bReturnRequested = TRUE;
         osCommand += " RETURNING ";
         osCommand += OGRPGEscapeColumnName(pszFIDColumn);
     }
+    else if (bSkipConflicts)
+        osCommand += " ON CONFLICT DO NOTHING";
 
     /* -------------------------------------------------------------------- */
     /*      Execute the insert.                                             */