[TD-5594]<fix>:calculate tag index in table meta when modify tag type

src/client/src/tscSQLParser.c

@@ -6078,10 +6078,12 @@ int32_t setAlterTableInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
 
     SSchema* pSchema = tscGetTableTagSchema(pTableMetaInfo->pTableMeta);
     int16_t numOfTags = tscGetNumOfTags(pTableMetaInfo->pTableMeta);
-    int16_t i;
+    int32_t numOfCols = tscGetNumOfColumns(pTableMetaInfo->pTableMeta);
+    int32_t tagIndex = columnIndex.columnIndex - numOfCols;
+    assert(tagIndex>=0);
     uint32_t nLen = 0;
-    for (i = 0; i < numOfTags; ++i) {
-      nLen += (i != columnIndex.columnIndex) ? pSchema[i].bytes : pItem->bytes;
+    for (int i = 0; i < numOfTags; ++i) {
+      nLen += (i != tagIndex) ? pSchema[i].bytes : pItem->bytes;
     }
     if (nLen >= TSDB_MAX_TAGS_LEN) {
       return invalidOperationMsg(pMsg, msg24);

tests/script/general/parser/alter_stable.sim

@@ -35,7 +35,10 @@ sql alter table tb1 set tag name = ""
 sql alter table tb1 set tag name = "shenzhen"
 sql alter table tb1 set tag len = 379
 
+# case TD-5594
+sql create stable st5520(ts timestamp, f int) tags(t0 bool, t1 nchar(4093), t2 nchar(1))
+sql_error alter stable st5520 modify tag t2 nchar(2);
 # test end   
 sql drop database $db
 
-system sh/exec.sh -n dnode1 -s stop -x SIGINT
\ No newline at end of file
+system sh/exec.sh -n dnode1 -s stop -x SIGINT