--- a/pkg/imports/errors.go	Mon May 06 17:45:24 2019 +0200
+++ b/pkg/imports/errors.go	Mon May 06 18:18:17 2019 +0200
@@ -29,13 +29,25 @@
 
 // Handle PostgreSQL error codes
 const (
-	noDataFound = "P0002"
+	foreignKeyViolation = "23503"
+	noDataFound         = "P0002"
 )
 
 type dbError pgx.PgError
 
 func (err dbError) Error() string {
 	switch err.Code {
+	case foreignKeyViolation:
+		switch err.SchemaName {
+		case "waterway":
+			switch err.TableName {
+			case "gauge_measurements":
+				switch err.ConstraintName {
+				case "gauge_key":
+					return "Referenced gauge is not in database"
+				}
+			}
+		}
 	case noDataFound:
 		// Most recent line from stacktrace contains name of failed function
 		recent := strings.SplitN(err.Where, "\n", 1)[0]

--- a/pkg/imports/gm.go	Mon May 06 17:45:24 2019 +0200
+++ b/pkg/imports/gm.go	Mon May 06 18:18:17 2019 +0200
@@ -4,13 +4,14 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 // License-Filename: LICENSES/AGPL-3.0.txt
 //
-// Copyright (C) 2018 by via donau
+// Copyright (C) 2018, 2019 by via donau
 //   – Österreichische Wasserstraßen-Gesellschaft mbH
 // Software engineering by Intevation GmbH
 //
 // Author(s):
 //  * Raimund Renkert <raimund.renkert@intevation.de>
 //  * Sascha L. Teichmann <sascha.teichmann@intevation.de>
+//  * Tom Gottfried <tom.gottfried@intevation.de>
 
 package imports
 
@@ -18,7 +19,6 @@
 	"context"
 	"database/sql"
 	"fmt"
-	"sort"
 	"strings"
 	"time"
 
@@ -40,16 +40,6 @@
 const GMJobKind JobKind = "gm"
 
 const (
-	listGaugesSQL = `
-SELECT
-  (location).country_code,
-  (location).locode,
-  (location).fairway_section,
-  (location).orc,
-  (location).hectometre
-FROM waterway.gauges
-WHERE (location).country_code = users.current_user_country()`
-
 	// Note: we do not expect corrections of data through this service.  So
 	// any constraint conflicts are triggered by actual redundat data which
 	// can be dropped.
@@ -164,39 +154,6 @@
 	)
 }
 
-func loadGauges(ctx context.Context, tx *sql.Tx) ([]string, error) {
-
-	rows, err := tx.QueryContext(ctx, listGaugesSQL)
-	if err != nil {
-		return nil, err
-	}
-	defer rows.Close()
-
-	var gauges []string
-
-	for rows.Next() {
-		var g models.Isrs
-		if err = rows.Scan(
-			&g.CountryCode,
-			&g.LoCode,
-			&g.FairwaySection,
-			&g.Orc,
-			&g.Hectometre,
-		); err != nil {
-			return nil, err
-		}
-		gauges = append(gauges, g.String())
-	}
-
-	if err = rows.Err(); err != nil {
-		return nil, err
-	}
-
-	sort.Strings(gauges)
-
-	return gauges, nil
-}
-
 func storeGaugeMeasurements(
 	ctx context.Context,
 	importID int64,
@@ -207,37 +164,19 @@
 
 	start := time.Now()
 
-	tx, err := conn.BeginTx(ctx, nil)
+	// TODO get date_issue for selected gauges
+	gids, err := doForGM(ctx, fetch, conn, feedback)
 	if err != nil {
-		return nil, err
-	}
-	defer tx.Rollback()
-
-	// Get available gauges from database for use as filter in SOAP request
-	gauges, err := loadGauges(ctx, tx)
-	if err != nil {
-		return nil, err
-	}
-
-	// TODO get date_issue for selected gauges
-	gids, err := doForGM(ctx, gauges, fetch, tx, feedback)
-	if err != nil {
-		feedback.Error("Error processing %d gauges: %v", len(gauges), err)
+		feedback.Error("Error processing gauges: %v", err)
 		return nil, err
 	}
 
 	if len(gids) == 0 {
-		feedback.Info("No new gauge measurements found")
 		return nil, UnchangedError("No new gauge measurements found")
 	}
 
-	if err = tx.Commit(); err != nil {
-		feedback.Info(
-			"Importing gauge measurements failed after %s", time.Since(start))
-		return nil, err
-	}
 	feedback.Info(
-		"Importing gauge measurements successfully took %s", time.Since(start))
+		"Importing gauge measurements took %s", time.Since(start))
 
 	// TODO: needs to be filled more useful.
 	summary := struct {
@@ -276,24 +215,17 @@
 
 func doForGM(
 	ctx context.Context,
-	gauges []string,
 	fetch func() ([]*nts.RIS_Message_Type, error),
-	tx *sql.Tx,
+	conn *sql.Conn,
 	feedback Feedback,
 ) ([]string, error) {
 
-	insertStmt, err := tx.PrepareContext(ctx, insertGMSQL)
+	insertStmt, err := conn.PrepareContext(ctx, insertGMSQL)
 	if err != nil {
 		return nil, err
 	}
 	defer insertStmt.Close()
 
-	// lookup to see if we have gauges in the database.
-	isKnown := func(s string) bool {
-		idx := sort.SearchStrings(gauges, s)
-		return idx < len(gauges) && gauges[idx] == s
-	}
-
 	result, err := fetch()
 	if err != nil {
 		return nil, err
@@ -310,10 +242,6 @@
 				continue
 			}
 			feedback.Info("Found measurements for %s", curr)
-			if !isKnown(curr) {
-				feedback.Warn("Gauge '%s' is not in database.", curr)
-				continue
-			}
 
 			var referenceCode string
 			if wrm.Reference_code == nil {
@@ -363,7 +291,7 @@
 				case err == sql.ErrNoRows:
 					// thats expected, nothing to do
 				case err != nil:
-					return nil, err
+					feedback.Warn(handleError(err).Error())
 				default:
 					newCnt++
 				}

--- a/schema/gemma.sql	Mon May 06 17:45:24 2019 +0200
+++ b/schema/gemma.sql	Mon May 06 18:18:17 2019 +0200
@@ -297,7 +297,7 @@
 
     CREATE TABLE gauge_measurements (
         id int PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
-        fk_gauge_id isrs NOT NULL REFERENCES gauges,
+        fk_gauge_id isrs NOT NULL CONSTRAINT gauge_key REFERENCES gauges,
         measure_date timestamp with time zone NOT NULL,
         country_code char(2) NOT NULL REFERENCES countries,
         -- TODO: add relations to stuff provided as enumerations