fix(migration): check if ldap2 already exists (#9674)

# Which Problems Are Solved

With v2.71.0 the `idp_templates6_ldap3` projection was created but never
filled, as it was a subtable. To fix this we altered the
`idp_templates6_ldap3` to `idp_templates6_ldap2` with v2.71.5.
This was unfortunately without a check that the `idp_templates_ldap2`was
already existing, which resulted in an error in the setup step.

# How the Problems Are Solved

Add check if `idp_templates6_ldap2` is already existing, before renaming
`idp_templates6_ldap3` -> `idp_templates6_ldap2`.

# Additional Changes

None

# Additional Context

Closes #9669

cmd/setup/52.go

@@ -2,15 +2,19 @@ package setup
 
 import (
 	"context"
+	"database/sql"
 	_ "embed"
+	"errors"
 
 	"github.com/zitadel/zitadel/internal/database"
 	"github.com/zitadel/zitadel/internal/eventstore"
 )
 
 var (
-	//go:embed 52.sql
+	//go:embed 52/alter.sql
 	renameTableIfNotExisting string
+	//go:embed 52/check.sql
+	checkIfTableIsExisting string
 )
 
 type IDPTemplate6LDAP2 struct {
@@ -18,7 +22,23 @@ type IDPTemplate6LDAP2 struct {
 }
 
 func (mig *IDPTemplate6LDAP2) Execute(ctx context.Context, _ eventstore.Event) error {
-	_, err := mig.dbClient.ExecContext(ctx, renameTableIfNotExisting)
+	var count int
+	err := mig.dbClient.QueryRowContext(ctx,
+		func(row *sql.Row) error {
+			if err := row.Scan(&count); err != nil {
+				return err
+			}
+			return row.Err()
+		},
+		checkIfTableIsExisting,
+	)
+	if err == nil {
+		return nil
+	}
+	if !errors.Is(err, sql.ErrNoRows) {
+		return err
+	}
+	_, err = mig.dbClient.ExecContext(ctx, renameTableIfNotExisting)
 	return err
 }
 

cmd/setup/52/check.sql

@@ -0,0 +1,4 @@
+SELECT 1
+FROM information_schema.tables
+WHERE table_schema = 'projections'
+  AND table_name = 'idp_templates6_ldap2';