Re: pg_migrator and handling dropped columns

Peter Eisentraut wrote:
> Tom Lane wrote:
> >> Is this acceptable to everyone?  We could name the option
> >> -u/--upgrade-compatible.
> >
> > If the switch is specifically for pg_upgrade support (enabling this as
> > well as any other hacks we find necessary), which seems like a good
> > idea, then don't chew up a short option letter for it.  There should be
> > a long form only.
>
> Note that pg_dump's output is already upgrade compatible.  That's what
> pg_dump is often used for after all.  I believe what we are after here
> is something like "in-place upgrade compatible" or "upgrade binary
> compatible".
>
> > And probably not even list it in the user documentation.
>
> I think we should still list it somewhere and say it is for use by
> in-place upgrade utilities.  It will only confuse people if it is not
> documented at all.

OK, I have completed the patch;  attached.

I ran into a little problem, as documented by this comment in
catalog/heap.c:

        /*
         * Set the type OID to invalid.  A dropped attribute's type link
         * cannot be relied on (once the attribute is dropped, the type might
         * be too). Fortunately we do not need the type row --- the only
         * really essential information is the type's typlen and typalign,
         * which are preserved in the attribute's attlen and attalign.  We set
         * atttypid to zero here as a means of catching code that incorrectly
         * expects it to be valid.
         */

Basically, drop column zeros pg_attribute.atttypid, and there doesn't
seem to be enough information left in pg_attribute to guess the typid
that, combined with atttypmod, would restore the proper values for
pg_attribute.atttypid and pg_attribute.attalign.  Therefore, I just
brute-forced an UPDATE into dump to set the values properly after
dropping the fake TEXT column.

I did a minimal documentation addition by adding something to the
"Notes" section of the manual pages.

Here is what a dump of a table with dropped columns looks like:

    --
    -- Name: test; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
    --

    CREATE TABLE test (
        x integer,
        "........pg.dropped.2........" TEXT
    );
    ALTER TABLE ONLY test DROP COLUMN "........pg.dropped.2........";

    -- For binary upgrade, recreate dropped column's length and alignment.
    UPDATE pg_attribute
    SET attlen = -1, attalign = 'i'
    WHERE   attname = '........pg.dropped.2........'
            AND attrelid =
            (
                    SELECT oid
                    FROM pg_class
                    WHERE   relnamespace = (SELECT oid FROM pg_namespace WHERE nspname = CURRENT_SCHEMA)
                            AND relname = 'test'
            );

    ALTER TABLE public.test OWNER TO postgres;

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +
Index: doc/src/sgml/ref/pg_dump.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/ref/pg_dump.sgml,v
retrieving revision 1.109
diff -c -c -r1.109 pg_dump.sgml
*** doc/src/sgml/ref/pg_dump.sgml    10 Feb 2009 00:55:21 -0000    1.109
--- doc/src/sgml/ref/pg_dump.sgml    17 Feb 2009 01:57:10 -0000
***************
*** 827,832 ****
--- 827,837 ----
     editing of the dump file might be required.
    </para>

+   <para>
+    <application>pg_dump</application> also supports a
+    <literal>--binary-upgrade</> option for upgrade utility usage.
+   </para>
+
   </refsect1>

   <refsect1 id="pg-dump-examples">
Index: doc/src/sgml/ref/pg_dumpall.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/ref/pg_dumpall.sgml,v
retrieving revision 1.75
diff -c -c -r1.75 pg_dumpall.sgml
*** doc/src/sgml/ref/pg_dumpall.sgml    7 Feb 2009 14:31:30 -0000    1.75
--- doc/src/sgml/ref/pg_dumpall.sgml    17 Feb 2009 01:57:10 -0000
***************
*** 489,494 ****
--- 489,499 ----
     locations.
    </para>

+   <para>
+    <application>pg_dump</application> also supports a
+    <literal>--binary-upgrade</> option for upgrade utility usage.
+   </para>
+
   </refsect1>


Index: src/bin/pg_dump/pg_dump.c
===================================================================
RCS file: /cvsroot/pgsql/src/bin/pg_dump/pg_dump.c,v
retrieving revision 1.521
diff -c -c -r1.521 pg_dump.c
*** src/bin/pg_dump/pg_dump.c    16 Feb 2009 23:06:55 -0000    1.521
--- src/bin/pg_dump/pg_dump.c    17 Feb 2009 01:57:10 -0000
***************
*** 99,104 ****
--- 99,106 ----
  /* default, if no "inclusion" switches appear, is to dump everything */
  static bool include_everything = true;

+ static int    binary_upgrade = 0;
+
  char        g_opaque_type[10];    /* name for the opaque type */

  /* placeholders for the delimiters for comments */
***************
*** 236,242 ****
      static int  outputNoTablespaces = 0;
      static int    use_setsessauth = 0;

!     static struct option long_options[] = {
          {"data-only", no_argument, NULL, 'a'},
          {"blobs", no_argument, NULL, 'b'},
          {"clean", no_argument, NULL, 'c'},
--- 238,245 ----
      static int  outputNoTablespaces = 0;
      static int    use_setsessauth = 0;

!     struct option long_options[] = {
!         {"binary-upgrade", no_argument, &binary_upgrade, 1},    /* not documented */
          {"data-only", no_argument, NULL, 'a'},
          {"blobs", no_argument, NULL, 'b'},
          {"clean", no_argument, NULL, 'c'},
***************
*** 4611,4616 ****
--- 4614,4621 ----
      int            i_attnotnull;
      int            i_atthasdef;
      int            i_attisdropped;
+     int            i_attlen;
+     int            i_attalign;
      int            i_attislocal;
      PGresult   *res;
      int            ntups;
***************
*** 4655,4661 ****
              appendPQExpBuffer(q, "SELECT a.attnum, a.attname, a.atttypmod, "
                                   "a.attstattarget, a.attstorage, t.typstorage, "
                                     "a.attnotnull, a.atthasdef, a.attisdropped, "
!                                  "a.attislocal, "
                     "pg_catalog.format_type(t.oid,a.atttypmod) AS atttypname "
               "FROM pg_catalog.pg_attribute a LEFT JOIN pg_catalog.pg_type t "
                                "ON a.atttypid = t.oid "
--- 4660,4666 ----
              appendPQExpBuffer(q, "SELECT a.attnum, a.attname, a.atttypmod, "
                                   "a.attstattarget, a.attstorage, t.typstorage, "
                                     "a.attnotnull, a.atthasdef, a.attisdropped, "
!                                    "a.attlen, a.attalign, a.attislocal, "
                     "pg_catalog.format_type(t.oid,a.atttypmod) AS atttypname "
               "FROM pg_catalog.pg_attribute a LEFT JOIN pg_catalog.pg_type t "
                                "ON a.atttypid = t.oid "
***************
*** 4674,4680 ****
              appendPQExpBuffer(q, "SELECT a.attnum, a.attname, "
                                "a.atttypmod, -1 AS attstattarget, a.attstorage, "
                                "t.typstorage, a.attnotnull, a.atthasdef, "
!                               "false AS attisdropped, false AS attislocal, "
                                "format_type(t.oid,a.atttypmod) AS atttypname "
                                "FROM pg_attribute a LEFT JOIN pg_type t "
                                "ON a.atttypid = t.oid "
--- 4679,4686 ----
              appendPQExpBuffer(q, "SELECT a.attnum, a.attname, "
                                "a.atttypmod, -1 AS attstattarget, a.attstorage, "
                                "t.typstorage, a.attnotnull, a.atthasdef, "
!                               "false AS attisdropped, 0 AS attlen, "
!                               "' ' AS attalign, false AS attislocal, "
                                "format_type(t.oid,a.atttypmod) AS atttypname "
                                "FROM pg_attribute a LEFT JOIN pg_type t "
                                "ON a.atttypid = t.oid "
***************
*** 4690,4696 ****
                                "-1 AS attstattarget, attstorage, "
                                "attstorage AS typstorage, "
                                "attnotnull, atthasdef, false AS attisdropped, "
!                               "false AS attislocal, "
                                "(SELECT typname FROM pg_type WHERE oid = atttypid) AS atttypname "
                                "FROM pg_attribute a "
                                "WHERE attrelid = '%u'::oid "
--- 4696,4703 ----
                                "-1 AS attstattarget, attstorage, "
                                "attstorage AS typstorage, "
                                "attnotnull, atthasdef, false AS attisdropped, "
!                               "0 AS attlen, ' ' AS attalign, "
!                                "false AS attislocal, "
                                "(SELECT typname FROM pg_type WHERE oid = atttypid) AS atttypname "
                                "FROM pg_attribute a "
                                "WHERE attrelid = '%u'::oid "
***************
*** 4714,4719 ****
--- 4721,4728 ----
          i_attnotnull = PQfnumber(res, "attnotnull");
          i_atthasdef = PQfnumber(res, "atthasdef");
          i_attisdropped = PQfnumber(res, "attisdropped");
+         i_attlen = PQfnumber(res, "attlen");
+         i_attalign = PQfnumber(res, "attalign");
          i_attislocal = PQfnumber(res, "attislocal");

          tbinfo->numatts = ntups;
***************
*** 4724,4729 ****
--- 4733,4740 ----
          tbinfo->attstorage = (char *) malloc(ntups * sizeof(char));
          tbinfo->typstorage = (char *) malloc(ntups * sizeof(char));
          tbinfo->attisdropped = (bool *) malloc(ntups * sizeof(bool));
+         tbinfo->attlen = (int *) malloc(ntups * sizeof(int));
+         tbinfo->attalign = (char *) malloc(ntups * sizeof(char));
          tbinfo->attislocal = (bool *) malloc(ntups * sizeof(bool));
          tbinfo->notnull = (bool *) malloc(ntups * sizeof(bool));
          tbinfo->attrdefs = (AttrDefInfo **) malloc(ntups * sizeof(AttrDefInfo *));
***************
*** 4747,4752 ****
--- 4758,4765 ----
              tbinfo->attstorage[j] = *(PQgetvalue(res, j, i_attstorage));
              tbinfo->typstorage[j] = *(PQgetvalue(res, j, i_typstorage));
              tbinfo->attisdropped[j] = (PQgetvalue(res, j, i_attisdropped)[0] == 't');
+             tbinfo->attlen[j] = atoi(PQgetvalue(res, j, i_attlen));
+             tbinfo->attalign[j] = *(PQgetvalue(res, j, i_attalign));
              tbinfo->attislocal[j] = (PQgetvalue(res, j, i_attislocal)[0] == 't');
              tbinfo->notnull[j] = (PQgetvalue(res, j, i_attnotnull)[0] == 't');
              tbinfo->attrdefs[j] = NULL; /* fix below */
***************
*** 4760,4765 ****
--- 4773,4793 ----

          PQclear(res);

+
+         /*
+          *    ALTER TABLE DROP COLUMN clears pg_attribute.atttypid, so we
+          *    set the column data type to 'TEXT;  we will later drop the
+          *    column.
+          */
+         if (binary_upgrade)
+         {
+             for (j = 0; j < ntups; j++)
+             {
+                 if (tbinfo->attisdropped[j])
+                     tbinfo->atttypnames[j] = strdup("TEXT");
+             }
+         }
+
          /*
           * Get info about column defaults
           */
***************
*** 9680,9686 ****
          for (j = 0; j < tbinfo->numatts; j++)
          {
              /* Is this one of the table's own attrs, and not dropped ? */
!             if (!tbinfo->inhAttrs[j] && !tbinfo->attisdropped[j])
              {
                  /* Format properly if not first attr */
                  if (actual_atts > 0)
--- 9708,9715 ----
          for (j = 0; j < tbinfo->numatts; j++)
          {
              /* Is this one of the table's own attrs, and not dropped ? */
!             if (!tbinfo->inhAttrs[j] &&
!                 (!tbinfo->attisdropped[j] || binary_upgrade))
              {
                  /* Format properly if not first attr */
                  if (actual_atts > 0)
***************
*** 9786,9791 ****
--- 9815,9867 ----

          appendPQExpBuffer(q, ";\n");

+         /*
+          * For binary-compatible heap files, we create dropped columns
+          * above and drop them here.
+          */
+         if (binary_upgrade)
+         {
+             for (j = 0; j < tbinfo->numatts; j++)
+             {
+                 if (tbinfo->attisdropped[j])
+                 {
+                     appendPQExpBuffer(q, "ALTER TABLE ONLY %s ",
+                                       fmtId(tbinfo->dobj.name));
+                     appendPQExpBuffer(q, "DROP COLUMN %s;\n",
+                                       fmtId(tbinfo->attnames[j]));
+
+                     /*
+                      *    ALTER TABLE DROP COLUMN clears pg_attribute.atttypid,
+                      *    so we have to set pg_attribute.attlen and
+                      *    pg_attribute.attalign values because that is what
+                      *    is used to skip over dropped columns in the heap tuples.
+                      *    We have atttypmod, but it seems impossible to know the
+                      *    correct data type that will yield pg_attribute values
+                      *    that match the old installation.
+                      *    See comment in backend/catalog/heap.c::RemoveAttributeById()
+                      */
+                     appendPQExpBuffer(q, "\n-- For binary upgrade, recreate dropped column's length and
alignment.\n");
+                     appendPQExpBuffer(q, "UPDATE pg_attribute\n"
+                                          "SET attlen = %d, "
+                                          "attalign = '%c'\n"
+                                          "WHERE    attname = '%s'\n"
+                                          "    AND attrelid = \n"
+                                          "    (\n"
+                                          "        SELECT oid\n"
+                                          "        FROM pg_class\n"
+                                          "        WHERE    relnamespace = "
+                                          "(SELECT oid FROM pg_namespace "
+                                          "WHERE nspname = CURRENT_SCHEMA)\n"
+                                          "            AND relname = '%s'\n"
+                                          "    );",
+                                          tbinfo->attlen[j],
+                                          tbinfo->attalign[j],
+                                          tbinfo->attnames[j],
+                                          tbinfo->dobj.name);
+                 }
+             }
+         }
+
          /* Loop dumping statistics and storage statements */
          for (j = 0; j < tbinfo->numatts; j++)
          {
Index: src/bin/pg_dump/pg_dump.h
===================================================================
RCS file: /cvsroot/pgsql/src/bin/pg_dump/pg_dump.h,v
retrieving revision 1.150
diff -c -c -r1.150 pg_dump.h
*** src/bin/pg_dump/pg_dump.h    2 Feb 2009 19:31:39 -0000    1.150
--- src/bin/pg_dump/pg_dump.h    17 Feb 2009 01:57:10 -0000
***************
*** 245,250 ****
--- 245,252 ----
      char       *attstorage;        /* attribute storage scheme */
      char       *typstorage;        /* type storage scheme */
      bool       *attisdropped;    /* true if attr is dropped; don't dump it */
+     int           *attlen;            /* attribute length, used by binary_upgrade */
+     char       *attalign;        /* attribute align, used by binary_upgrade */
      bool       *attislocal;        /* true if attr has local definition */

      /*
Index: src/bin/pg_dump/pg_dumpall.c
===================================================================
RCS file: /cvsroot/pgsql/src/bin/pg_dump/pg_dumpall.c,v
retrieving revision 1.113
diff -c -c -r1.113 pg_dumpall.c
*** src/bin/pg_dump/pg_dumpall.c    22 Jan 2009 20:16:08 -0000    1.113
--- src/bin/pg_dump/pg_dumpall.c    17 Feb 2009 01:57:10 -0000
***************
*** 90,97 ****
      const char *std_strings;
      int            c,
                  ret;

!     static struct option long_options[] = {
          {"data-only", no_argument, NULL, 'a'},
          {"clean", no_argument, NULL, 'c'},
          {"inserts", no_argument, NULL, 'd'},
--- 90,99 ----
      const char *std_strings;
      int            c,
                  ret;
+     int            binary_upgrade = 0;

!     struct option long_options[] = {
!         {"binary-upgrade", no_argument, &binary_upgrade, 1},    /* not documented */
          {"data-only", no_argument, NULL, 'a'},
          {"clean", no_argument, NULL, 'c'},
          {"inserts", no_argument, NULL, 'd'},
***************
*** 310,315 ****
--- 312,319 ----
      }

      /* Add long options to the pg_dump argument list */
+     if (binary_upgrade)
+         appendPQExpBuffer(pgdumpopts, " --binary-upgrade");
      if (disable_dollar_quoting)
          appendPQExpBuffer(pgdumpopts, " --disable-dollar-quoting");
      if (disable_triggers)