MDEV-38347 Debugging functions

Extend current dbug_print* functions in such a way as to facilitate easy
high level debugging.  Introduce a single overloaded print function
defined in dbp.h, DBUG_PRINT_FUNCTION, settable to your preference.
Allow a shell environment variable DBUG_PRINT_FUNCTION to override
this definition

CMakeLists.txt

@@ -377,6 +377,11 @@ ELSEIF(TRASH_FREED_MEMORY MATCHES "AUTO" AND NOT WIN32 AND NOT WITH_VALGRIND AND
   SET(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DTRASH_FREED_MEMORY")
 ENDIF()
 
+# override preferred overloaded debugging routine name
+IF(DEFINED ENV{DBUG_PRINT_FUNCTION})
+  ADD_DEFINITIONS(-DDBUG_PRINT_FUNCTION=$ENV{DBUG_PRINT_FUNCTION})
+ENDIF()
+
 INCLUDE(wsrep)
 
 # Set commonly used variables

sql/dbp.h

@@ -0,0 +1,48 @@
+/* Copyright (c) 2026, MariaDB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#ifndef __DBP_H__
+#define __DBP_H__
+
+#include <sys/types.h>
+#include "my_global.h"
+#include "my_json_writer.h"
+
+#ifndef DBUG_PRINT_FUNCTION
+#  define DBUG_PRINT_FUNCTION dbug_print
+#endif
+#define DBUG_PRINT_ROW  dbp_row
+#define DBUG_PRINT_TRACE  dbp_trace
+#define DBUG_ITEM_BUFFER_SIZE 2048
+extern void dbug_strlcat( char *dest, uint dest_size, const char *src);
+
+extern void dbug_sprintfcat(char *dest, uint dest_size, const char *format, ...);
+extern const char *dbug_add_print_field(Field *field);
+extern void dbug_add_print_field_value(Field *field);
+
+#define DBUG_CAT(...) dbug_strlcat(dbug_big_buffer, DBUG_BIG_BUFFER_SIZE, \
+                                   __VA_ARGS__)
+
+#define DBUG_SPRINTF_CAT(...) dbug_sprintfcat(dbug_big_buffer,\
+                                DBUG_BIG_BUFFER_SIZE, __VA_ARGS__)
+
+#define DBUG_TRASH_CHAR      0xa5
+
+#define DBUG_BIG_BUFFER_SIZE 20480
+static char dbug_big_buffer[DBUG_BIG_BUFFER_SIZE];
+
+#define DBUG_ROW_BUFFER_SIZE 1024
+
+#endif

sql/item.cc

@@ -11467,9 +11467,12 @@ const char *dbug_print_unit(SELECT_LEX_UNIT *un)
     return "Couldn't fit into buffer";
 }
 
+#if 0
+// these overloads now defined in dbp.cc
 const char *dbug_print(Item *x)            { return dbug_print_item(x);   }
 const char *dbug_print(SELECT_LEX *x)      { return dbug_print_select(x); }
 const char *dbug_print(SELECT_LEX_UNIT *x) { return dbug_print_unit(x);   }
+#endif
 
 
 /*
@@ -11989,3 +11992,5 @@ bool ignored_list_includes_table(ignored_tables_list_t list, TABLE_LIST *tbl)
   }
   return false;
 }
+
+#include "dbp.cc"

sql/opt_range.cc

@@ -298,6 +298,22 @@ public:
 
   bool without_ranges() { return keys_map.is_clear_all(); }
   bool without_imerges() { return merges.is_empty(); }
+#ifndef DBUG_OFF
+  key_map get_keys_map()
+  {
+    return keys_map;
+  }
+
+  SEL_ARG *get_key(uint keyno)
+  {
+    return keys[keyno];
+  }
+
+  uint get_type()
+  {
+    return (uint)type;
+  }
+#endif
 };
 
 
@@ -17007,3 +17023,70 @@ void print_keyparts_name(String *out, const KEY_PART_INFO *key_part,
   }
   out->append(STRING_WITH_LEN(")"));
 }
+
+#ifndef DBUG_OFF
+#include "dbp.h"
+
+// "1 <= a < 'x'": a range as a string, values quoted SQL style
+void dbug_add_print_sel_arg(SEL_ARG *arg, KEY_PART *part)
+{
+  DBUG_CAT("\"");
+  if (!(arg->min_flag & NO_MIN_RANGE))
+  {
+    store_key_image_to_rec(part->field, arg->min_value, part->length);
+    dbug_add_print_field_value(part->field);
+    if (arg->min_flag & NEAR_MIN)
+      DBUG_CAT(" < ");
+    else
+      DBUG_CAT(" <= ");
+  }
+
+  DBUG_SPRINTF_CAT("%s", part->field->field_name.str);
+
+  if (!(arg->max_flag & NO_MAX_RANGE))
+  {
+    if (arg->max_flag & NEAR_MAX)
+      DBUG_CAT(" < ");
+    else
+      DBUG_CAT(" <= ");
+    store_key_image_to_rec(part->field, arg->max_value, part->length);
+    dbug_add_print_field_value(part->field);
+  }
+  DBUG_CAT("\"");
+}
+
+
+const char *DBUG_PRINT_FUNCTION(SEL_ARG *arg, KEY_PART *part)
+{
+  *dbug_big_buffer= (char)0;
+  DBUG_SPRINTF_CAT("(SEL_ARG*)%p", arg);
+  dbug_add_print_sel_arg(arg, part);
+  return dbug_big_buffer;
+}
+
+
+const char *DBUG_PRINT_FUNCTION(SEL_TREE *arg, KEY_PART *parts)
+{
+  static const char *type_names[]=
+    {"IMPOSSIBLE", "ALWAYS", "MAYBE", "KEY", "KEY_SMALLER"};
+  *dbug_big_buffer= (char)0;
+  DBUG_SPRINTF_CAT("(SEL_TREE*)%p{type:%s, keys:[", arg,
+                   arg->type < array_elements(type_names) ?
+                     type_names[arg->type] : "UNKNOWN");
+  key_map::Iterator it(arg->keys_map);
+  int key_no;
+  bool first= true;
+  while ((key_no= it++) != key_map::Iterator::BITMAP_END)
+  {
+    SEL_ARG *key1= arg->get_key(key_no);
+    if (!first)
+      DBUG_CAT(", ");
+    first= false;
+    dbug_add_print_sel_arg( key1, parts+key1->part );
+  }
+  DBUG_CAT("]}");
+
+  return dbug_big_buffer;
+}
+
+#endif