proxysql/deps/mariadb-client-library/cr_new_stmt_metadata_removal.patch

diff --git libmariadb/mariadb_stmt.c libmariadb/mariadb_stmt.c
index bbc2831..2168065 100644
--- libmariadb/mariadb_stmt.c
+++ libmariadb/mariadb_stmt.c
@@ -2013,7 +2013,61 @@ int stmt_read_execute_response(MYSQL_STMT *stmt)
     stmt->state= MYSQL_STMT_WAITING_USE_OR_STORE;
     /* in certain cases parameter types can change: For example see bug
        4026 (SELECT ?), so we need to update field information */
-    if (mysql->field_count == stmt->field_count)
+
+    /* ProxySQL #1574: We never set the CR_NEW_STMT_METADATA error because
+       we get the information about the changes on the metadata from the
+       column definitions in the resulset itself. This change allows ProxySQL
+       to avoid a extra query for MEDATADA fetch that otherwise would need
+       to be performed in case of 'CR_NEW_STMT_METADATA' being returned
+       from the library.
+    */
+    /*********************************************************************/
+    if (mysql->field_count != stmt->field_count)
+    {
+      MA_MEM_ROOT *fields_ma_alloc_root=
+                   &((MADB_STMT_EXTENSION *)stmt->extension)->fields_ma_alloc_root;
+      uint i;
+
+      // 'ma_free_root' will free all the allocated memory for 'fields_ma_alloc_root'
+      // for this reason we need to allocate again all the fields and also allocate
+      // the required space for 'MYSQL_BIND'.
+      ma_free_root(fields_ma_alloc_root, MYF(0));
+      if (!(stmt->bind= (MYSQL_BIND *)ma_alloc_root(fields_ma_alloc_root,
+              sizeof(MYSQL_BIND) * mysql->field_count)) ||
+          !(stmt->fields= (MYSQL_FIELD *)ma_alloc_root(fields_ma_alloc_root,
+              sizeof(MYSQL_FIELD) * mysql->field_count)))
+      {
+        SET_CLIENT_STMT_ERROR(stmt, CR_OUT_OF_MEMORY, SQLSTATE_UNKNOWN, 0);
+        return(1);
+      }
+      memset(stmt->bind, 0, sizeof(MYSQL_BIND) * mysql->field_count);
+      stmt->field_count= mysql->field_count;
+
+      // We need to copy again all the data of freed fields in case the number
+      // of fields doesn't match because the number of fields isn't the expected.
+      /*********************************************************************/
+      for (i=0; i < stmt->field_count; i++)
+      {
+        memcpy(&stmt->fields[i], &mysql->fields[i], sizeof(MYSQL_FIELD));
+
+        stmt->fields[i].extension= 0; /* not in use yet */
+        if (mysql->fields[i].db)
+          stmt->fields[i].db= ma_strdup_root(fields_ma_alloc_root, mysql->fields[i].db);
+        if (mysql->fields[i].table)
+          stmt->fields[i].table= ma_strdup_root(fields_ma_alloc_root, mysql->fields[i].table);
+        if (mysql->fields[i].org_table)
+          stmt->fields[i].org_table= ma_strdup_root(fields_ma_alloc_root, mysql->fields[i].org_table);
+        if (mysql->fields[i].name)
+          stmt->fields[i].name= ma_strdup_root(fields_ma_alloc_root, mysql->fields[i].name);
+        if (mysql->fields[i].org_name)
+          stmt->fields[i].org_name= ma_strdup_root(fields_ma_alloc_root, mysql->fields[i].org_name);
+        if (mysql->fields[i].catalog)
+          stmt->fields[i].catalog= ma_strdup_root(fields_ma_alloc_root, mysql->fields[i].catalog);
+        if (mysql->fields[i].def)
+          stmt->fields[i].def= ma_strdup_root(fields_ma_alloc_root, mysql->fields[i].def);
+      }
+      /*********************************************************************/
+    }
     {
       uint i;
       for (i=0; i < stmt->field_count; i++)
@@ -2025,12 +2079,8 @@ int stmt_read_execute_response(MYSQL_STMT *stmt)
         stmt->fields[i].charsetnr= mysql->fields[i].charsetnr;
         stmt->fields[i].max_length= mysql->fields[i].max_length;
       }
-    } else
-    {
-      /* table was altered, see test_wl4166_2  */
-      SET_CLIENT_STMT_ERROR(stmt, CR_NEW_STMT_METADATA, SQLSTATE_UNKNOWN, 0);
-      return(1);
     }
+    /*********************************************************************/
   }
   return(0);
 }