fix upper expression return empty string in oracle mode bug

src/sql/engine/expr/ob_expr.cpp

@@ -622,6 +622,7 @@ int ObExpr::eval_one_datum_of_batch(ObEvalCtx &ctx, common::ObDatum *&datum) con
     } else {
       reset_datum_ptr(frame, ctx.get_batch_size(), ctx.get_batch_idx());
       ret = eval_func_(*this, ctx, *datum);
+      CHECK_STRING_LENGTH((*this), (*datum));
       if (OB_SUCC(ret)) {
         ObBitVector *evaluated_flags = to_bit_vector(frame + eval_flags_off_);
         evaluated_flags->set(ctx.get_batch_idx());
@@ -676,6 +677,16 @@ int ObExpr::do_eval_batch(ObEvalCtx &ctx,
           info->cnt_ = size;
           info->evaluated_ = true;
         }
+        #ifndef NDEBUG
+          if (is_oracle_mode() && (ob_is_string_tc(datum_meta_.type_) || ob_is_raw(datum_meta_.type_))) {
+            ObDatum *datum = reinterpret_cast<ObDatum *>(frame + datum_off_);
+            for (int64_t i = 0; i < size; i++) {
+              if (!skip.contain(i) && 0 == datum[i].len_ && !datum[i].is_null()) {
+                SQL_ENG_LOG(ERROR, "unexpected datum length", KPC(this));
+              }
+            }
+          }
+        #endif
       } else {
         ObDatum *datum = reinterpret_cast<ObDatum *>(frame + datum_off_);
         ObDatum *datum_end = datum + size;
@@ -706,6 +717,7 @@ int expr_default_eval_batch_func(const ObExpr &expr,
       // set current evaluate index
       batch_info_guard.set_batch_idx(i);
       ret = expr.eval_func_(expr, ctx, datum[i]);
+      CHECK_STRING_LENGTH(expr, datum[i]);
       evaluated_flags->set(i);
       if (datum[i].is_null()) {
         got_null = true;

src/sql/engine/expr/ob_expr.h

@@ -351,6 +351,18 @@ typedef common::ObFixedArray<common::ObString, common::ObIAllocator> ObStrValues
 #define EVAL_FUNC_ARG_DECL const ObExpr &expr, ObEvalCtx &ctx, ObDatum &expr_datum
 #define EVAL_FUNC_ARG_LIST expr, ctx, expr_datum
 
+
+#ifndef NDEBUG
+#define CHECK_STRING_LENGTH(expr, datum)   \
+  if (OB_SUCC(ret) && 0 == datum.len_ && !datum.is_null() && is_oracle_mode() &&\
+      (ob_is_string_tc(expr.datum_meta_.type_) || ob_is_raw(expr.datum_meta_.type_))) {  \
+    SQL_ENG_LOG(ERROR, "unexpected datum length", K(expr)); \
+  }
+#else
+#define CHECK_STRING_LENGTH(expr, datum)
+#endif
+
+
 // default evaluate batch function which call eval() for every datum of batch.
 extern int expr_default_eval_batch_func(BATCH_EVAL_FUNC_ARG_DECL);
 
@@ -1016,6 +1028,7 @@ OB_INLINE int ObExpr::eval(ObEvalCtx &ctx, common::ObDatum *&datum) const
         datum->ptr_ = frame + res_buf_off_;
       }
       ret = eval_func_(*this, ctx, *datum);
+      CHECK_STRING_LENGTH((*this), (*datum));
       if (OB_LIKELY(common::OB_SUCCESS == ret)) {
         eval_info->evaluated_ = true;
       } else {

src/sql/engine/expr/ob_expr_lower.cpp

@@ -446,7 +446,12 @@ int ObExprLowerUpper::calc_common(const ObExpr &expr, ObEvalCtx &ctx,
       }
     }
     if (OB_SUCC(ret)) {
-      expr_datum.set_string(str_result);
+      if (OB_UNLIKELY(is_oracle_mode() && str_result.length() == 0
+                      && ob_is_string_tc(expr.datum_meta_.type_))) {
+        expr_datum.set_null();
+      } else {
+        expr_datum.set_string(str_result);
+      }
     }
   }
   return ret;