Add support for two step DB upsert

server/codegen/assets/templates/gocode/store/rdbms/rdbms.go.tpl

@@ -80,8 +80,29 @@ func (s *Store) Upsert{{ .expIdent }}(ctx context.Context, {{ template "extraArg
 			return
 		}
 
-		if err = s.Exec(ctx, {{ .ident }}UpsertQuery(s.Dialect.GOQU(), rr[i])); err != nil {
-			return
+		// @todo this solution is ok for now but could be problematic when we start
+		// batching together DB operations.
+		if s.Dialect.Nuances().TwoStepUpsert {
+			var rsp sql.Result
+			rsp, err = s.ExecR(ctx, {{ .ident }}UpdateQuery(s.Dialect.GOQU(), rr[i]))
+			if err != nil {
+				return
+			}
+			if c, err := rsp.RowsAffected(); err != nil {
+				return err
+			} else if c > 0 {
+				continue
+			}
+
+			err = s.Exec(ctx, {{ .ident }}InsertQuery(s.Dialect.GOQU(), rr[i]))
+			if err != nil {
+				return
+			}
+		} else {
+			err = s.Exec(ctx, {{ .ident }}UpsertQuery(s.Dialect.GOQU(), rr[i]))
+			if err != nil {
+				return
+			}
 		}
 	}
 

server/store/adapters/rdbms/drivers/dialect.go

@@ -3,6 +3,7 @@ package drivers
 import (
 	"encoding/json"
 	"fmt"
+
 	"github.com/cortezaproject/corteza/server/pkg/dal"
 	"github.com/cortezaproject/corteza/server/pkg/ql"
 	"github.com/cortezaproject/corteza/server/store/adapters/rdbms/ddl"
@@ -17,6 +18,13 @@ type (
 		// use of aliases inside HAVING clause and
 		// MySQL does not.
 		HavingClauseMustUseAlias bool
+
+		// TwoStepUpsert allows support for databases which don't have an upsert
+		// or we simply couldn't figure out how to make work.
+		//
+		// TwoStepUpsert uses the context from the update statement to figure out
+		// if it needs to do an insert.
+		TwoStepUpsert bool
 	}
 
 	Dialect interface {

server/store/adapters/rdbms/rdbms_store.go

@@ -114,17 +114,28 @@ func (s Store) Healthcheck(ctx context.Context) error {
 	return s.Ping(ctx)
 }
 
+// Exec executes the SQL and drops the result
 func (s Store) Exec(ctx context.Context, q sqlizer) error {
+	_, err := s.exec(ctx, q)
+	return err
+}
+
+// ExecR executes the SQL and returns the result
+func (s Store) ExecR(ctx context.Context, q sqlizer) (rs sql.Result, _ error) {
+	return s.exec(ctx, q)
+}
+
+func (s Store) exec(ctx context.Context, q sqlizer) (rs sql.Result, _ error) {
 	var (
 		query, args, err = q.ToSQL()
 	)
 
 	if err != nil {
-		return fmt.Errorf("could not build query: %w", err)
+		return rs, fmt.Errorf("could not build query: %w", err)
 	}
 
-	_, err = s.DB.ExecContext(ctx, query, args...)
-	return store.HandleError(err, s.ErrorHandler)
+	rs, err = s.DB.ExecContext(ctx, query, args...)
+	return rs, store.HandleError(err, s.ErrorHandler)
 }
 
 func (s Store) Query(ctx context.Context, q sqlizer) (*sql.Rows, error) {