Ignore duplicate metrics

CHANGES.rst

@@ -5,6 +5,7 @@ CHANGES for CrateDB Prometheus Adapter
 Unreleased
 ==========
 
+- Add option to configure primary key conflict behaviour.
 
 2024-01-23 0.5.1
 ================

crate.go

@@ -13,7 +13,7 @@ import (
 	"github.com/prometheus/common/model"
 )
 
-const crateWriteStatement = `INSERT INTO metrics ("labels", "labels_hash", "timestamp", "value", "valueRaw") VALUES ($1, $2, $3, $4, $5)`
+const crateWriteStatement = `INSERT INTO metrics ("labels", "labels_hash", "timestamp", "value", "valueRaw") VALUES ($1, $2, $3, $4, $5) ON CONFLICT DO NOTHING`
 
 type crateRow struct {
 	labels     model.Metric
@@ -112,17 +112,17 @@ func newCrateEndpoint(ep *endpointConfig) *crateEndpoint {
 }
 
 func (c *crateEndpoint) endpoint() endpoint.Endpoint {
-	/**
-	 * Initialize connection pools lazily here instead of in `newCrateEndpoint()`,
-	 * so that the adapter does not crash on startup if the endpoint is unavailable.
-	**/
-	return func(ctx context.Context, request interface{}) (response interface{}, err error) {
-
+		/**
+		* Initialize connection pools lazily here instead of in `newCrateEndpoint()`,
+		* so that the adapter does not crash on startup if the endpoint is unavailable.
+		**/
+		return func(ctx context.Context, request interface{}) (response interface{}, err error) {
+		
 		// Initialize database connection pools.
-		err = c.createPools(ctx)
+			err = c.createPools(ctx)
 
 		// Dispatch by request type.
-		switch r := request.(type) {
+			switch r := request.(type) {
 		case *crateWriteRequest:
 			return nil, c.write(ctx, r)
 		case *crateReadRequest: