fix tmp block clear

be/src/vec/exec/scan/vscanner.cpp

@@ -22,6 +22,7 @@
 #include "common/config.h"
 #include "pipeline/exec/scan_operator.h"
 #include "runtime/descriptors.h"
+#include "util/defer_op.h"
 #include "util/runtime_profile.h"
 #include "vec/core/column_with_type_and_name.h"
 #include "vec/exec/scan/vscan_node.h"
@@ -152,19 +153,21 @@ Status VScanner::get_block(RuntimeState* state, Block* block, bool* eof) {
 }
 
 Status VScanner::_filter_output_block(Block* block) {
+    Defer clear_tmp_block([&]() {
+        auto all_column_names = block->get_names();
+        for (auto& name : all_column_names) {
+            if (name.rfind(BeConsts::BLOCK_TEMP_COLUMN_PREFIX, 0) == 0) {
+                block->erase(name);
+            }
+        }
+    });
     if (block->has(BeConsts::BLOCK_TEMP_COLUMN_SCANNER_FILTERED)) {
         // scanner filter_block is already done (only by _topn_next currently), just skip it
         return Status::OK();
     }
     auto old_rows = block->rows();
     Status st = VExprContext::filter_block(_conjuncts, block, block->columns());
     _counter.num_rows_unselected += old_rows - block->rows();
-    auto all_column_names = block->get_names();
-    for (auto& name : all_column_names) {
-        if (name.rfind(BeConsts::BLOCK_TEMP_COLUMN_PREFIX, 0) == 0) {
-            block->erase(name);
-        }
-    }
     return st;
 }