enh: write idx ahead of writing its log entry in WAL

source/libs/wal/src/walWrite.c

@@ -449,6 +449,11 @@ static FORCE_INLINE int32_t walWriteImpl(SWal *pWal, int64_t index, tmsg_t msgTy
   pWal->writeHead.cksumBody = walCalcBodyCksum(body, bodyLen);
   wDebug("vgId:%d, wal write log %ld, msgType: %s", pWal->cfg.vgId, index, TMSG_INFO(msgType));
 
+  code = walWriteIndex(pWal, index, offset);
+  if (code < 0) {
+    goto END;
+  }
+
   if (taosWriteFile(pWal->pLogFile, &pWal->writeHead, sizeof(SWalCkHead)) != sizeof(SWalCkHead)) {
     terrno = TAOS_SYSTEM_ERROR(errno);
     wError("vgId:%d, file:%" PRId64 ".log, failed to write since %s", pWal->cfg.vgId, walGetLastFileFirstVer(pWal),
@@ -465,11 +470,6 @@ static FORCE_INLINE int32_t walWriteImpl(SWal *pWal, int64_t index, tmsg_t msgTy
     goto END;
   }
 
-  code = walWriteIndex(pWal, index, offset);
-  if (code < 0) {
-    goto END;
-  }
-
   // set status
   if (pWal->vers.firstVer == -1) pWal->vers.firstVer = index;
   pWal->vers.lastVer = index;