more alter table

source/dnode/mnode/impl/src/mndStb.c

@@ -386,7 +386,7 @@ static void *mndBuildVCreateStbReq(SMnode *pMnode, SVgObj *pVgroup, SStbObj *pSt
   req.schema.sver = pStb->version;
   req.schema.pSchema = pStb->pColumns;
   req.schemaTag.nCols = pStb->numOfTags;
-  req.schemaTag.nCols = 0;
+  req.schemaTag.sver = 1;
   req.schemaTag.pSchema = pStb->pTags;
 
   if (req.rollup) {

source/dnode/vnode/src/meta/metaTable.c

@@ -599,10 +599,41 @@ static int metaUpdateTableTagVal(SMeta *pMeta, int64_t version, SVAlterTbReq *pA
     goto _err;
   }
 
-  {
-    // TODO:
+  if (iCol == 0) {
+    // TODO : need to update tag index
   }
 
+  ctbEntry.version = version;
+  SKVRowBuilder kvrb = {0};
+  const SKVRow  pOldTag = (const SKVRow)ctbEntry.ctbEntry.pTags;
+  SKVRow        pNewTag = NULL;
+
+  tdInitKVRowBuilder(&kvrb);
+  for (int32_t i = 0; i < pTagSchema->nCols; i++) {
+    SSchema *pCol = &pTagSchema->pSchema[i];
+    if (iCol == i) {
+      tdAddColToKVRow(&kvrb, pCol->colId, pAlterTbReq->pTagVal, pAlterTbReq->nTagVal);
+    } else {
+      void *p = tdGetKVRowValOfCol(pOldTag, pCol->colId);
+      if (p) {
+        if (IS_VAR_DATA_TYPE(pCol->type)) {
+          tdAddColToKVRow(&kvrb, pCol->colId, p, varDataTLen(p));
+        } else {
+          tdAddColToKVRow(&kvrb, pCol->colId, p, pCol->bytes);
+        }
+      }
+    }
+  }
+
+  ctbEntry.ctbEntry.pTags = tdGetKVRowFromBuilder(&kvrb);
+  tdDestroyKVRowBuilder(&kvrb);
+
+  // save to table.db
+  metaSaveToTbDb(pMeta, &ctbEntry);
+
+  // save to uid.idx
+  tdbDbUpsert(pMeta->pUidIdx, &ctbEntry.uid, sizeof(tb_uid_t), &version, sizeof(version), &pMeta->txn);
+
   if (ctbEntry.pBuf) taosMemoryFree(ctbEntry.pBuf);
   if (stbEntry.pBuf) tdbFree(stbEntry.pBuf);
   tdbDbcClose(pTbDbc);