add debugging messages

go/vt/discovery/healthcheck.go

@@ -855,6 +855,7 @@ func (hc *HealthCheckImpl) TabletConnection(alias *topodata.TabletAlias, target
 	hc.mu.Unlock()
 	if thc == nil || thc.Conn == nil {
 		// TODO: test that throws this error
+		log.Warning("NOT_FOUND: tablet: %v is either down or nonexistent", alias)
 		return nil, vterrors.Errorf(vtrpc.Code_NOT_FOUND, "tablet: %v is either down or nonexistent", alias)
 	}
 	return thc.Connection(hc), nil

go/vt/vtgate/engine/set.go

@@ -540,6 +540,7 @@ func (svss *SysVarSetAware) Execute(ctx context.Context, vcursor VCursor, env *e
 			return vterrors.NewErrorf(vtrpcpb.Code_INVALID_ARGUMENT, vterrors.WrongValueForVar, "variable 'session_track_gtids' can't be set to the value of '%s'", str)
 		}
 	default:
+		log.Warning("NOT_FOUOND: unknown system variable '%s'", svss.Name)
 		return vterrors.NewErrorf(vtrpcpb.Code_NOT_FOUND, vterrors.UnknownSystemVariable, "unknown system variable '%s'", svss.Name)
 	}
 

go/vt/vtgate/plan_execute.go

@@ -201,12 +201,14 @@ func (e *Executor) handleTransactions(
 	case sqlparser.StmtSRollback:
 		qr, err := e.handleSavepoint(ctx, safeSession, plan.Original, "Rollback Savepoint", logStats, func(query string) (*sqltypes.Result, error) {
 			// Error as there is no transaction, so there is no savepoint that exists.
+			log.Warning("NOT_FOUND: SAVEPOINT does not exist: %s", query)
 			return nil, vterrors.NewErrorf(vtrpcpb.Code_NOT_FOUND, vterrors.SPDoesNotExist, "SAVEPOINT does not exist: %s", query)
 		}, vcursor.ignoreMaxMemoryRows)
 		return qr, err
 	case sqlparser.StmtRelease:
 		qr, err := e.handleSavepoint(ctx, safeSession, plan.Original, "Release Savepoint", logStats, func(query string) (*sqltypes.Result, error) {
 			// Error as there is no transaction, so there is no savepoint that exists.
+			log.Warning("NOT_FOUND: SAVEPOINT does not exist: %s", query)
 			return nil, vterrors.NewErrorf(vtrpcpb.Code_NOT_FOUND, vterrors.SPDoesNotExist, "SAVEPOINT does not exist: %s", query)
 		}, vcursor.ignoreMaxMemoryRows)
 		return qr, err

go/vt/vtgate/scatter_conn.go

@@ -831,6 +831,7 @@ func lockInfo(target *querypb.Target, session *SafeSession, lockFuncType sqlpars
 	info := &shardActionInfo{actionNeeded: nothing}
 	if session.LockSession != nil {
 		if !proto.Equal(target, session.LockSession.Target) {
+			log.Warning("NOT_FOUND: target does match the existing lock session target: (%v, %v)", target, session.LockSession.Target)
 			return nil, vterrors.Errorf(vtrpcpb.Code_NOT_FOUND, "target does match the existing lock session target: (%v, %v)", target, session.LockSession.Target)
 		}
 		info.reservedID = session.LockSession.ReservedId

go/vt/vtgate/semantics/derived_table.go

@@ -19,6 +19,7 @@ package semantics
 import (
 	"strings"
 
+	"vitess.io/vitess/go/vt/log"
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
 	"vitess.io/vitess/go/vt/sqlparser"
 	"vitess.io/vitess/go/vt/vterrors"
@@ -183,6 +184,7 @@ func (dt *DerivedTable) getExprFor(s string) (sqlparser.Expr, error) {
 			return dt.cols[i], nil
 		}
 	}
+	log.Warning("NOT_FOUND: Unknown column '%s' in 'field list'", s)
 	return nil, vterrors.NewErrorf(vtrpcpb.Code_NOT_FOUND, vterrors.BadFieldError, "Unknown column '%s' in 'field list'", s)
 }
 

go/vt/vtgate/tabletgateway.go

@@ -494,7 +494,8 @@ func (gw *TabletGateway) updateDefaultConnCollation(tablet *topodatapb.Tablet) {
 		return
 	}
 	if gw.defaultConnCollation.Load() != tablet.DefaultConnCollation {
-		log.Warning("this Vitess cluster has tablets with different default connection collations")
+		log.Warning("this Vitess cluster has tablets with different default connection collations: gw: %v, tablet:%v, host:%v",
+			gw.defaultConnCollation.Load(), tablet.DefaultConnCollation, tablet.Hostname)
 	}
 }
 

go/vt/vtgate/vindexes/vschema.go

@@ -29,6 +29,7 @@ import (
 	"vitess.io/vitess/go/mysql/collations"
 	"vitess.io/vitess/go/sqlescape"
 	"vitess.io/vitess/go/sqltypes"
+	"vitess.io/vitess/go/vt/log"
 	querypb "vitess.io/vitess/go/vt/proto/query"
 	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 	vschemapb "vitess.io/vitess/go/vt/proto/vschema"
@@ -493,6 +494,9 @@ func buildKeyspaceReferences(vschema *VSchema, ksvschema *KeyspaceSchema) error
 			if vterrors.Code(err) != vtrpcpb.Code_NOT_FOUND || vterrors.ErrState(err) != vterrors.BadDb {
 				return err
 			}
+			log.Warning("NOT_FOUND: source %q references a non-existent keyspace %q",
+				source,
+				sourceKsname)
 			return vterrors.Errorf(
 				vtrpcpb.Code_NOT_FOUND,
 				"source %q references a non-existent keyspace %q",
@@ -501,6 +505,10 @@ func buildKeyspaceReferences(vschema *VSchema, ksvschema *KeyspaceSchema) error
 			)
 		}
 		if sourceT == nil {
+			log.Warning("NOT_FOUND: source %q references a table %q that is not present in the VSchema of keyspace %q",
+				source,
+				sourceTname,
+				sourceKsname)
 			return vterrors.Errorf(
 				vtrpcpb.Code_NOT_FOUND,
 				"source %q references a table %q that is not present in the VSchema of keyspace %q",
@@ -606,6 +614,8 @@ func buildTables(ks *vschemapb.Keyspace, vschema *VSchema, ksvschema *KeyspaceSc
 			}
 			t.Type = table.Type
 		default:
+			log.Warning("NOT_FOUND: unidentified table type %s",
+				table.Type)
 			return vterrors.Errorf(
 				vtrpcpb.Code_NOT_FOUND,
 				"unidentified table type %s",
@@ -828,6 +838,9 @@ func resolveAutoIncrement(source *vschemapb.SrvVSchema, vschema *VSchema, parser
 				// Better to remove the table than to leave it partially initialized.
 				delete(ksvschema.Tables, tname)
 				delete(vschema.globalTables, tname)
+				log.Warning("NOT_FOUND: cannot resolve sequence %s: %s",
+					table.AutoIncrement.Sequence,
+					err.Error())
 				ksvschema.Error = vterrors.Errorf(
 					vtrpcpb.Code_NOT_FOUND,
 					"cannot resolve sequence %s: %s",