Do not check for enabled triggers / FKs for fallback workflow of PG i…

…f session_replication_role session variable is used (#2322)

Adding GRANT SQL for granting the SET on session_replication_role to source-db-user to utilize it in Fallback case for import data to source
Added a check in GetEnabledTriggersAndFks(), to not fetch the triggers/Fks in case this session parameter is used.

guardrails-scripts/yb-voyager-pg-grant-migration-permissions.sql

@@ -228,5 +228,14 @@ GRANT pg_read_all_stats to :voyager_user;
         WHERE 
             schema_name = ANY(string_to_array(:'schema_list', ','))
         \gexec
+
+        DO $$ 
+        BEGIN 
+        IF (substring((SELECT setting FROM pg_catalog.pg_settings WHERE name = 'server_version'), '^[0-9]+')::int >= 15) THEN
+            RAISE NOTICE 'Granting set on PARAMETER session_replication_role TO %;', current_setting('myvars.voyager_user');
+            EXECUTE format('GRANT SET ON PARAMETER session_replication_role TO %I;', current_setting('myvars.voyager_user'));
+        END IF;
+        END $$;
+
     \endif
 \endif

yb-voyager/src/tgtdb/postgres.go

@@ -33,6 +33,7 @@ import (
 	_ "github.com/jackc/pgx/v5/stdlib"
 	"github.com/samber/lo"
 	log "github.com/sirupsen/logrus"
+	"golang.org/x/exp/slices"
 
 	"github.com/yugabyte/yb-voyager/yb-voyager/src/callhome"
 	"github.com/yugabyte/yb-voyager/yb-voyager/src/constants"
@@ -115,6 +116,9 @@ func (pg *TargetPostgreSQL) Init() error {
 	if err != nil {
 		return err
 	}
+	if len(pg.tconf.SessionVars) == 0 {
+		pg.tconf.SessionVars = getPGSessionInitScript(pg.tconf)
+	}
 	schemas := strings.Split(pg.tconf.Schema, ",")
 	schemaList := strings.Join(schemas, "','") // a','b','c
 	checkSchemaExistsQuery := fmt.Sprintf(
@@ -241,12 +245,11 @@ func (pg *TargetPostgreSQL) InitConnPool() error {
 		pg.tconf.Parallelism = fetchDefaultParallelJobs(tconfs, PG_DEFAULT_PARALLELISM_FACTOR)
 		log.Infof("Using %d parallel jobs by default. Use --parallel-jobs to specify a custom value", pg.tconf.Parallelism)
 	}
-
 	params := &ConnectionParams{
 		NumConnections:    pg.tconf.Parallelism,
 		NumMaxConnections: pg.tconf.Parallelism,
 		ConnUriList:       targetUriList,
-		SessionInitScript: getYBSessionInitScript(pg.tconf),
+		SessionInitScript: pg.tconf.SessionVars,
 		// works fine as we check the support of any session variable before using it in the script.
 		// So upsert and disable transaction will never be used for PG
 	}
@@ -1054,6 +1057,10 @@ func (pg *TargetPostgreSQL) getSchemaList() []string {
 }
 
 func (pg *TargetPostgreSQL) GetEnabledTriggersAndFks() (enabledTriggers []string, enabledFks []string, err error) {
+	if slices.Contains(pg.tconf.SessionVars, SET_SESSION_REPLICATE_ROLE_TO_REPLICA) {
+		//Not check for any triggers / FKs in case this session parameter is used
+		return nil, nil, nil
+	}
 	querySchemaArray := pg.getSchemaList()
 	querySchemaList := strings.Join(querySchemaArray, ",")
 

yb-voyager/src/tgtdb/tconf.go

@@ -57,6 +57,7 @@ type TargetConf struct {
 	Parallelism                 int           `json:"parallelism"`
 	EnableYBAdaptiveParallelism utils.BoolStr `json:"enable_adaptive_parallelism"`
 	MaxParallelism              int           `json:"max_parallelism"` // in case adaptive parallelism is enabled.
+	SessionVars                 []string      `json:"session_vars"`
 }
 
 func (t *TargetConf) Clone() *TargetConf {

yb-voyager/src/tgtdb/yugabytedb.go

@@ -119,6 +119,10 @@ func (yb *TargetYugabyteDB) Init() error {
 		return err
 	}
 
+	if len(yb.tconf.SessionVars) == 0 {
+		yb.tconf.SessionVars = getYBSessionInitScript(yb.tconf)
+	}
+
 	checkSchemaExistsQuery := fmt.Sprintf(
 		"SELECT count(nspname) FROM pg_catalog.pg_namespace WHERE nspname = '%s';",
 		yb.tconf.Schema)
@@ -241,7 +245,7 @@ func (yb *TargetYugabyteDB) InitConnPool() error {
 		NumConnections:    yb.tconf.Parallelism,
 		NumMaxConnections: yb.tconf.MaxParallelism,
 		ConnUriList:       targetUriList,
-		SessionInitScript: getYBSessionInitScript(yb.tconf),
+		SessionInitScript: yb.tconf.SessionVars,
 	}
 	yb.connPool = NewConnectionPool(params)
 	redactedParams := &ConnectionParams{}
@@ -996,6 +1000,17 @@ const (
 	ERROR_MSG_PERMISSION_DENIED                 = "permission denied"
 )
 
+func getPGSessionInitScript(tconf *TargetConf) []string {
+	var sessionVars []string
+	if checkSessionVariableSupport(tconf, SET_CLIENT_ENCODING_TO_UTF8) {
+		sessionVars = append(sessionVars, SET_CLIENT_ENCODING_TO_UTF8)
+	}
+	if checkSessionVariableSupport(tconf, SET_SESSION_REPLICATE_ROLE_TO_REPLICA) {
+		sessionVars = append(sessionVars, SET_SESSION_REPLICATE_ROLE_TO_REPLICA)
+	}
+	return sessionVars
+}
+
 func getYBSessionInitScript(tconf *TargetConf) []string {
 	var sessionVars []string
 	if checkSessionVariableSupport(tconf, SET_CLIENT_ENCODING_TO_UTF8) {
@@ -1067,7 +1082,7 @@ func checkSessionVariableSupport(tconf *TargetConf, sqlStmt string) bool {
 				if !utils.AskPrompt("Are you sure you want to proceed?") {
 					utils.ErrExit("Aborting import.")
 				}
-				return true
+				return false // support is not there even if the target user doesn't have privileges to set this parameter.
 			}
 			utils.ErrExit("error while executing sqlStatement: %q: %v", sqlStmt, err)
 		} else {