Add dbug_print_sel_arg() debugging help function

sql/opt_range.cc

@@ -14786,6 +14786,113 @@ static void print_ror_scans_arr(TABLE *table, const char *msg,
   DBUG_VOID_RETURN;
 }
 
+static String dbug_print_sel_arg_buf;
+
+static void
+print_sel_arg_key(Field *field, const uchar *key, String *out)
+{
+  TABLE *table= field->table;
+  my_bitmap_map *old_sets[2];
+  dbug_tmp_use_all_columns(table, old_sets, table->read_set, table->write_set);
+
+  if (field->real_maybe_null())
+  {
+    if (*key)
+    {
+      out->append("NULL");
+      goto end;
+    }
+    key++;					// Skip null byte
+  }
+
+  field->set_key_image(key, field->pack_length());
+
+  if (field->type() == MYSQL_TYPE_BIT)
+    (void) field->val_int_as_str(out, 1);
+  else
+    field->val_str(out);
+
+end:
+  dbug_tmp_restore_column_maps(table->read_set, table->write_set, old_sets);
+}
+
+
+/*
+  @brief
+    Produce a string representation of an individual SEL_ARG and return pointer
+    to it
+
+  @detail
+    Intended usage:
+
+     (gdb) p dbug_print_sel_arg(ptr)
+*/
+
+const char *dbug_print_sel_arg(SEL_ARG *sel_arg)
+{
+  StringBuffer<64> buf;
+  String &out= dbug_print_sel_arg_buf;
+  out.length(0);
+
+  if (!sel_arg)
+  {
+    out.append("NULL");
+    goto end;
+  }
+
+  out.append("SEL_ARG(");
+
+  const char *stype;
+  switch(sel_arg->type) {
+  case SEL_ARG::IMPOSSIBLE:
+    stype="IMPOSSIBLE";
+    break;
+  case SEL_ARG::MAYBE:
+    stype="MAYBE";
+    break;
+  case SEL_ARG::MAYBE_KEY:
+    stype="MAYBE_KEY";
+    break;
+  case SEL_ARG::KEY_RANGE:
+  default:
+    stype=nullptr;
+  }
+
+  if (stype)
+  {
+    out.append("type=");
+    out.append(stype);
+    goto end;
+  }
+
+  if (sel_arg->min_flag & NO_MIN_RANGE)
+    out.append("-inf");
+  else
+  {
+    print_sel_arg_key(sel_arg->field, sel_arg->min_value, &buf);
+    out.append(buf);
+  }
+
+  out.append((sel_arg->min_flag & NEAR_MIN)? "<" : "<=");
+
+  out.append(sel_arg->field->field_name);
+
+  out.append((sel_arg->max_flag & NEAR_MAX)? "<" : "<=");
+
+  if (sel_arg->max_flag & NO_MAX_RANGE)
+    out.append("+inf");
+  else
+  {
+    print_sel_arg_key(sel_arg->field, sel_arg->max_value, &buf);
+    out.append(buf);
+  }
+
+  out.append(")");
+
+end:
+  return dbug_print_sel_arg_buf.c_ptr_safe();
+}
+
 
 /*****************************************************************************
 ** Print a quick range for debugging