Proposal: PageLayout footprint - Mailing list pgsql-hackers

Current content of control file is insufficient to check if database is
compatible with postgres server. I think we should create footprint file which
will contains all page data structures and their member offset and length (and
maybe more).

As a first step which is useful at least for in-place-upgrade is footprint
switch which prints page layout structures. I attach WIP patch.

I'm thinking also to create pg_footprint view with (version, structure name,
attribute, offset, size) columns. But I'm not sure about usefulness of this
catalog (?maybe for regression tests?).

    Comments, ideas?

        Thanks Zdenek



--
Zdenek Kotala              Sun Microsystems
Prague, Czech Republic     http://sun.com/postgresql

*** pgsql_footprint.76863ce445f3/src/backend/main/main.c    po srp 11 06:48:20 2008
--- pgsql_footprint/src/backend/main/main.c    ne srp 10 19:15:03 2008
***************
*** 34,39 ****
--- 34,40 ----
  #include <sys/param.h>
  #endif

+ #include "access/itup.h"
  #include "bootstrap/bootstrap.h"
  #include "postmaster/postmaster.h"
  #include "tcop/tcopprot.h"
***************
*** 44,50 ****
  #include "libpq/pqsignal.h"
  #endif

-
  const char *progname;


--- 45,50 ----
***************
*** 52,60 ****
  static void help(const char *progname);
  static void check_root(const char *progname);
  static char *get_current_username(const char *progname);


-
  int
  main(int argc, char *argv[])
  {
--- 52,60 ----
  static void help(const char *progname);
  static void check_root(const char *progname);
  static char *get_current_username(const char *progname);
+ static void footprint(void);


  int
  main(int argc, char *argv[])
  {
***************
*** 149,154 ****
--- 149,159 ----
              puts("postgres (PostgreSQL) " PG_VERSION);
              exit(0);
          }
+         if ( strcmp(argv[1], "--footprint") == 0 )
+         {
+             footprint();
+             exit(0);
+         }
      }

      /*
***************
*** 301,306 ****
--- 306,312 ----
      printf(_("  -t pa|pl|ex     show timings after each query\n"));
      printf(_("  -T              send SIGSTOP to all backend servers if one dies\n"));
      printf(_("  -W NUM          wait NUM seconds to allow attach from a debugger\n"));
+     printf(_("  --footprint     output page structure layout, then exit\n"));

      printf(_("\nOptions for single-user mode:\n"));
      printf(_("  --single        selects single-user mode (must be first argument)\n"));
***************
*** 396,398 ****
--- 402,439 ----
      return name;
  #endif
  }
+
+ #define PRT_STRUCT(str) \
+     printf("%s (%i/%i)\n", CppAsString(str), sizeof(str), MAXALIGN(sizeof(str)));
+ #define PRT_ATTR(str, attr) \
+     printf("\t%s - %i,%i\n", CppAsString(attr), offsetof(str,attr), sizeof(((str *)0)->attr));
+
+ static void
+ footprint(void)
+ {
+     PRT_STRUCT(PageHeaderData);
+     PRT_ATTR(PageHeaderData, pd_lsn);
+     PRT_ATTR(PageHeaderData, pd_tli);
+     PRT_ATTR(PageHeaderData, pd_flags);
+     PRT_ATTR(PageHeaderData, pd_lower);
+     PRT_ATTR(PageHeaderData, pd_upper);
+     PRT_ATTR(PageHeaderData, pd_special);
+     PRT_ATTR(PageHeaderData, pd_pagesize_version);
+     PRT_ATTR(PageHeaderData, pd_prune_xid);
+     PRT_ATTR(PageHeaderData, pd_linp);
+
+     PRT_STRUCT(HeapTupleHeaderData);
+     PRT_ATTR(HeapTupleHeaderData, t_choice.t_heap.t_xmin);
+     PRT_ATTR(HeapTupleHeaderData, t_choice.t_heap.t_xmax);
+     PRT_ATTR(HeapTupleHeaderData, t_choice.t_heap.t_field3.t_cid);
+     PRT_ATTR(HeapTupleHeaderData, t_ctid);
+     PRT_ATTR(HeapTupleHeaderData, t_infomask2);
+     PRT_ATTR(HeapTupleHeaderData, t_infomask);
+     PRT_ATTR(HeapTupleHeaderData, t_hoff);
+     PRT_ATTR(HeapTupleHeaderData, t_bits);
+
+     PRT_STRUCT(IndexTupleData);
+     PRT_ATTR(IndexTupleData, t_tid);
+     PRT_ATTR(IndexTupleData, t_info);
+ }
+