Re: Distinct types

Peter Eisentraut wrote:
> Here is an implementation of distinct types,

I'm withdrawing this patch from the current commit fest for further
work.  For the record, I have attached the current patch, including the
documentation work by Jeff Davis.
Index: doc/src/sgml/ref/create_domain.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/ref/create_domain.sgml,v
retrieving revision 1.32
diff -u -3 -p -r1.32 create_domain.sgml
--- doc/src/sgml/ref/create_domain.sgml    14 Nov 2008 10:22:46 -0000    1.32
+++ doc/src/sgml/ref/create_domain.sgml    25 Nov 2008 10:13:18 -0000
@@ -58,6 +58,12 @@ where <replaceable class="PARAMETER">con
    Define a domain rather than setting up each table's constraint
    individually.
   </para>
+
+  <para>
+   Domains are similar to distinct types, described in <xref
+   linkend="sql-createtype">, except that you can specify defaults or
+   constraints, and a domain can be implicitly cast to its base type.
+  </para>
  </refsect1>

  <refsect1>
Index: doc/src/sgml/ref/create_type.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/ref/create_type.sgml,v
retrieving revision 1.78
diff -u -3 -p -r1.78 create_type.sgml
--- doc/src/sgml/ref/create_type.sgml    14 Nov 2008 10:22:46 -0000    1.78
+++ doc/src/sgml/ref/create_type.sgml    25 Nov 2008 10:13:18 -0000
@@ -27,6 +27,8 @@ CREATE TYPE <replaceable class="paramete
 CREATE TYPE <replaceable class="parameter">name</replaceable> AS ENUM
     ( '<replaceable class="parameter">label</replaceable>' [, ... ] )

+CREATE TYPE <replaceable class="parameter">name</replaceable> AS <replaceable
class="parameter">data_type</replaceable>
+
 CREATE TYPE <replaceable class="parameter">name</replaceable> (
     INPUT = <replaceable class="parameter">input_function</replaceable>,
     OUTPUT = <replaceable class="parameter">output_function</replaceable>
@@ -96,10 +98,25 @@ CREATE TYPE <replaceable class="paramete
   </refsect2>

   <refsect2>
+   <title>Distinct Types</title>
+
+   <para>
+    The third form of <command>CREATE TYPE</command> creates a
+    distinct type. Distinct types are similar to domains, as described
+    in <xref linkend="sql-createdomain">, except that they do not have
+    defaults or constraints, and they cannot be implicitly cast to
+    their base type. Distinct types are useful to avoid making
+    mistakes by comparing two unrelated values that happen to be the
+    same type, such as two integers representing supplier number and
+    part number.
+   </para>
+  </refsect2>
+
+  <refsect2>
    <title>Base Types</title>

   <para>
-   The third form of <command>CREATE TYPE</command> creates a new base type
+   The fourth form of <command>CREATE TYPE</command> creates a new base type
    (scalar type).  To create a new base type, you must be a superuser.
    (This restriction is made because an erroneous type definition could
    confuse or even crash the server.)
Index: src/backend/commands/typecmds.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/commands/typecmds.c,v
retrieving revision 1.126
diff -u -3 -p -r1.126 typecmds.c
--- src/backend/commands/typecmds.c    2 Nov 2008 01:45:28 -0000    1.126
+++ src/backend/commands/typecmds.c    25 Nov 2008 10:13:18 -0000
@@ -648,7 +648,7 @@ RemoveTypeById(Oid typeOid)

 /*
  * DefineDomain
- *        Registers a new domain.
+ *        Registers a new domain or distinct type.
  */
 void
 DefineDomain(CreateDomainStmt *stmt)
@@ -721,18 +721,27 @@ DefineDomain(CreateDomainStmt *stmt)
     basetypeoid = HeapTupleGetOid(typeTup);

     /*
-     * Base type must be a plain base type, another domain or an enum. Domains
+     * Base type must be a plain base type, another domain, distinct type, or an enum. Domains
      * over pseudotypes would create a security hole.  Domains over composite
      * types might be made to work in the future, but not today.
      */
     typtype = baseType->typtype;
     if (typtype != TYPTYPE_BASE &&
         typtype != TYPTYPE_DOMAIN &&
+        typtype != TYPTYPE_DISTINCT &&
         typtype != TYPTYPE_ENUM)
-        ereport(ERROR,
-                (errcode(ERRCODE_DATATYPE_MISMATCH),
-                 errmsg("\"%s\" is not a valid base type for a domain",
-                        TypeNameToString(stmt->typename))));
+    {
+        if (stmt->distinct_type)
+            ereport(ERROR,
+                    (errcode(ERRCODE_DATATYPE_MISMATCH),
+                     errmsg("\"%s\" is not a valid base type for a distinct type",
+                            TypeNameToString(stmt->typename))));
+        else
+            ereport(ERROR,
+                    (errcode(ERRCODE_DATATYPE_MISMATCH),
+                     errmsg("\"%s\" is not a valid base type for a domain",
+                            TypeNameToString(stmt->typename))));
+    }

     /* passed by value */
     byValue = baseType->typbyval;
@@ -938,7 +947,7 @@ DefineDomain(CreateDomainStmt *stmt)
                    InvalidOid,    /* relation oid (n/a here) */
                    0,            /* relation kind (ditto) */
                    internalLength,        /* internal size */
-                   TYPTYPE_DOMAIN,        /* type-type (domain type) */
+                   stmt->distinct_type ? TYPTYPE_DISTINCT : TYPTYPE_DOMAIN,        /* type-type (distinct type or
domain)*/ 
                    category,    /* type-category */
                    false,        /* domain types are never preferred */
                    delimiter,    /* array element delimiter */
Index: src/backend/executor/functions.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/executor/functions.c,v
retrieving revision 1.128
diff -u -3 -p -r1.128 functions.c
--- src/backend/executor/functions.c    31 Oct 2008 21:07:55 -0000    1.128
+++ src/backend/executor/functions.c    25 Nov 2008 10:13:18 -0000
@@ -1092,6 +1092,7 @@ check_sql_fn_retval(Oid func_id, Oid ret
     fn_typtype = get_typtype(rettype);

     if (fn_typtype == TYPTYPE_BASE ||
+        fn_typtype == TYPTYPE_DISTINCT ||
         fn_typtype == TYPTYPE_DOMAIN ||
         fn_typtype == TYPTYPE_ENUM ||
         rettype == VOIDOID)
Index: src/backend/nodes/copyfuncs.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v
retrieving revision 1.413
diff -u -3 -p -r1.413 copyfuncs.c
--- src/backend/nodes/copyfuncs.c    24 Nov 2008 08:46:03 -0000    1.413
+++ src/backend/nodes/copyfuncs.c    25 Nov 2008 10:13:18 -0000
@@ -2659,6 +2659,7 @@ _copyCreateDomainStmt(CreateDomainStmt *
     COPY_NODE_FIELD(domainname);
     COPY_NODE_FIELD(typename);
     COPY_NODE_FIELD(constraints);
+    COPY_SCALAR_FIELD(distinct_type);

     return newnode;
 }
Index: src/backend/nodes/equalfuncs.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v
retrieving revision 1.338
diff -u -3 -p -r1.338 equalfuncs.c
--- src/backend/nodes/equalfuncs.c    24 Nov 2008 08:46:03 -0000    1.338
+++ src/backend/nodes/equalfuncs.c    25 Nov 2008 10:13:18 -0000
@@ -1342,6 +1342,7 @@ _equalCreateDomainStmt(CreateDomainStmt
     COMPARE_NODE_FIELD(domainname);
     COMPARE_NODE_FIELD(typename);
     COMPARE_NODE_FIELD(constraints);
+    COMPARE_SCALAR_FIELD(distinct_type);

     return true;
 }
Index: src/backend/parser/gram.y
===================================================================
RCS file: /cvsroot/pgsql/src/backend/parser/gram.y,v
retrieving revision 2.640
diff -u -3 -p -r2.640 gram.y
--- src/backend/parser/gram.y    24 Nov 2008 08:46:03 -0000    2.640
+++ src/backend/parser/gram.y    25 Nov 2008 10:13:18 -0000
@@ -5623,6 +5623,16 @@ CreateDomainStmt:
                     n->domainname = $3;
                     n->typename = $5;
                     n->constraints = $6;
+                    n->distinct_type = FALSE;
+                    $$ = (Node *)n;
+                }
+            | CREATE TYPE_P any_name AS Typename
+                {
+                    CreateDomainStmt *n = makeNode(CreateDomainStmt);
+                    n->domainname = $3;
+                    n->typename = $5;
+                    n->constraints = NIL;
+                    n->distinct_type = TRUE;
                     $$ = (Node *)n;
                 }
         ;
@@ -9477,7 +9487,6 @@ unreserved_keyword:
             | ENABLE_P
             | ENCODING
             | ENCRYPTED
-            | ENUM_P
             | ESCAPE
             | EXCLUDING
             | EXCLUSIVE
@@ -9664,6 +9673,7 @@ col_name_keyword:
             | COALESCE
             | DEC
             | DECIMAL_P
+            | ENUM_P
             | EXISTS
             | EXTRACT
             | FLOAT_P
Index: src/backend/parser/keywords.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/parser/keywords.c,v
retrieving revision 1.205
diff -u -3 -p -r1.205 keywords.c
--- src/backend/parser/keywords.c    27 Oct 2008 09:37:47 -0000    1.205
+++ src/backend/parser/keywords.c    25 Nov 2008 10:13:18 -0000
@@ -157,7 +157,7 @@ const ScanKeyword ScanKeywords[] = {
     {"encoding", ENCODING, UNRESERVED_KEYWORD},
     {"encrypted", ENCRYPTED, UNRESERVED_KEYWORD},
     {"end", END_P, RESERVED_KEYWORD},
-    {"enum", ENUM_P, UNRESERVED_KEYWORD},
+    {"enum", ENUM_P, COL_NAME_KEYWORD},
     {"escape", ESCAPE, UNRESERVED_KEYWORD},
     {"except", EXCEPT, RESERVED_KEYWORD},
     {"excluding", EXCLUDING, UNRESERVED_KEYWORD},
Index: src/backend/parser/parse_coerce.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/parser/parse_coerce.c,v
retrieving revision 2.171
diff -u -3 -p -r2.171 parse_coerce.c
--- src/backend/parser/parse_coerce.c    31 Oct 2008 08:39:21 -0000    2.171
+++ src/backend/parser/parse_coerce.c    25 Nov 2008 10:13:18 -0000
@@ -1867,15 +1867,25 @@ find_coercion_pathway(Oid targetTypeId,
     *funcid = InvalidOid;

     /* Perhaps the types are domains; if so, look at their base types */
-    if (OidIsValid(sourceTypeId))
+    if (OidIsValid(sourceTypeId) && get_typtype(sourceTypeId) == TYPTYPE_DOMAIN)
         sourceTypeId = getBaseType(sourceTypeId);
-    if (OidIsValid(targetTypeId))
+    if (OidIsValid(targetTypeId) && get_typtype(targetTypeId) == TYPTYPE_DOMAIN)
         targetTypeId = getBaseType(targetTypeId);

     /* Domains are always coercible to and from their base type */
     if (sourceTypeId == targetTypeId)
         return COERCION_PATH_RELABELTYPE;

+    /* Distinct types are castable AS ASSIGNMENT to and from their base types */
+    if (ccontext >= COERCION_ASSIGNMENT
+        && ((OidIsValid(sourceTypeId)
+             && get_typtype(sourceTypeId) == TYPTYPE_DISTINCT
+             && getDirectBaseType(sourceTypeId) == targetTypeId)
+            || (OidIsValid(targetTypeId)
+                && get_typtype(targetTypeId) == TYPTYPE_DISTINCT
+                && getDirectBaseType(targetTypeId) == sourceTypeId)))
+        return COERCION_PATH_RELABELTYPE;
+
     /* Look in pg_cast */
     tuple = SearchSysCache(CASTSOURCETARGET,
                            ObjectIdGetDatum(sourceTypeId),
@@ -2033,6 +2043,7 @@ find_typmod_coercion_function(Oid typeId
     /* Check for a varlena array type (and not a domain) */
     if (typeForm->typelem != InvalidOid &&
         typeForm->typlen == -1 &&
+        typeForm->typtype != TYPTYPE_DISTINCT &&
         typeForm->typtype != TYPTYPE_DOMAIN)
     {
         /* Yes, switch our attention to the element type */
Index: src/backend/tcop/utility.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/tcop/utility.c,v
retrieving revision 1.301
diff -u -3 -p -r1.301 utility.c
--- src/backend/tcop/utility.c    7 Nov 2008 18:25:06 -0000    1.301
+++ src/backend/tcop/utility.c    25 Nov 2008 10:13:18 -0000
@@ -1291,7 +1291,11 @@ CreateCommandTag(Node *parsetree)
             break;

         case T_CreateDomainStmt:
-            tag = "CREATE DOMAIN";
+        {
+            CreateDomainStmt *stmt = (CreateDomainStmt *) parsetree;
+
+            tag = (stmt->distinct_type) ? "CREATE TYPE" : "CREATE DOMAIN";
+        }
             break;

         case T_CreateSchemaStmt:
Index: src/backend/utils/adt/format_type.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/format_type.c,v
retrieving revision 1.50
diff -u -3 -p -r1.50 format_type.c
--- src/backend/utils/adt/format_type.c    25 Mar 2008 22:42:44 -0000    1.50
+++ src/backend/utils/adt/format_type.c    25 Nov 2008 10:13:18 -0000
@@ -147,6 +147,7 @@ format_type_internal(Oid type_oid, int32

     if (array_base_type != InvalidOid &&
         typeform->typstorage != 'p' &&
+        typeform->typtype != TYPTYPE_DISTINCT &&
         typeform->typtype != TYPTYPE_DOMAIN)
     {
         /* Switch our attention to the array element type */
Index: src/backend/utils/adt/xml.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/xml.c,v
retrieving revision 1.81
diff -u -3 -p -r1.81 xml.c
--- src/backend/utils/adt/xml.c    10 Nov 2008 18:02:20 -0000    1.81
+++ src/backend/utils/adt/xml.c    25 Nov 2008 10:13:18 -0000
@@ -2872,7 +2872,7 @@ map_sql_typecoll_to_xmlschema_types(List
         }
     }

-    /* add base types of domains */
+    /* add base types of distinct types and domains */
     foreach(cell0, uniquetypes)
     {
         Oid            typid = lfirst_oid(cell0);
@@ -3056,7 +3056,7 @@ map_sql_type_to_xmlschema_type(Oid typeo
                 break;

             default:
-                if (get_typtype(typeoid) == TYPTYPE_DOMAIN)
+                if (get_typtype(typeoid) == TYPTYPE_DISTINCT || get_typtype(typeoid) == TYPTYPE_DOMAIN)
                 {
                     Oid            base_typeoid;
                     int32        base_typmod = -1;
Index: src/backend/utils/cache/lsyscache.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v
retrieving revision 1.160
diff -u -3 -p -r1.160 lsyscache.c
--- src/backend/utils/cache/lsyscache.c    28 Sep 2008 19:51:40 -0000    1.160
+++ src/backend/utils/cache/lsyscache.c    25 Nov 2008 10:13:18 -0000
@@ -2032,7 +2032,7 @@ get_typdefault(Oid typid)

 /*
  * getBaseType
- *        If the given type is a domain, return its base type;
+ *        If the given type is a distinct type or domain, return its base type;
  *        otherwise return the type's own OID.
  */
 Oid
@@ -2045,7 +2045,7 @@ getBaseType(Oid typid)

 /*
  * getBaseTypeAndTypmod
- *        If the given type is a domain, return its base type and typmod;
+ *        If the given type is a distinct type or domain, return its base type and typmod;
  *        otherwise return the type's own OID, and leave *typmod unchanged.
  *
  * Note that the "applied typmod" should be -1 for every domain level
@@ -2069,9 +2069,9 @@ getBaseTypeAndTypmod(Oid typid, int32 *t
         if (!HeapTupleIsValid(tup))
             elog(ERROR, "cache lookup failed for type %u", typid);
         typTup = (Form_pg_type) GETSTRUCT(tup);
-        if (typTup->typtype != TYPTYPE_DOMAIN)
+        if (typTup->typtype != TYPTYPE_DISTINCT && typTup->typtype != TYPTYPE_DOMAIN)
         {
-            /* Not a domain, so done */
+            /* Not a distinct type or domain, so done */
             ReleaseSysCache(tup);
             break;
         }
@@ -2087,6 +2087,30 @@ getBaseTypeAndTypmod(Oid typid, int32 *t
 }

 /*
+ * getDirectBaseType
+ *        If the given type is a distinct type or domain, return its direct base type;
+ *        otherwise return the type's own OID.
+ */
+Oid
+getDirectBaseType(Oid typid)
+{
+    HeapTuple    tup;
+    Form_pg_type typTup;
+
+    tup = SearchSysCache(TYPEOID,
+                         ObjectIdGetDatum(typid),
+                         0, 0, 0);
+    if (!HeapTupleIsValid(tup))
+        elog(ERROR, "cache lookup failed for type %u", typid);
+    typTup = (Form_pg_type) GETSTRUCT(tup);
+    if (typTup->typtype == TYPTYPE_DISTINCT || typTup->typtype == TYPTYPE_DOMAIN)
+        typid = typTup->typbasetype;
+
+    ReleaseSysCache(tup);
+    return typid;
+}
+
+/*
  * get_typavgwidth
  *
  *      Given a type OID and a typmod value (pass -1 if typmod is unknown),
Index: src/backend/utils/fmgr/funcapi.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/fmgr/funcapi.c,v
retrieving revision 1.42
diff -u -3 -p -r1.42 funcapi.c
--- src/backend/utils/fmgr/funcapi.c    25 Aug 2008 22:42:34 -0000    1.42
+++ src/backend/utils/fmgr/funcapi.c    25 Nov 2008 10:13:18 -0000
@@ -643,6 +643,7 @@ get_type_func_class(Oid typid)
         case TYPTYPE_COMPOSITE:
             return TYPEFUNC_COMPOSITE;
         case TYPTYPE_BASE:
+        case TYPTYPE_DISTINCT:
         case TYPTYPE_DOMAIN:
         case TYPTYPE_ENUM:
             return TYPEFUNC_SCALAR;
Index: src/bin/pg_dump/pg_dump.c
===================================================================
RCS file: /cvsroot/pgsql/src/bin/pg_dump/pg_dump.c,v
retrieving revision 1.505
diff -u -3 -p -r1.505 pg_dump.c
--- src/bin/pg_dump/pg_dump.c    9 Nov 2008 21:24:32 -0000    1.505
+++ src/bin/pg_dump/pg_dump.c    25 Nov 2008 10:13:18 -0000
@@ -134,6 +134,7 @@ static void dumpNamespace(Archive *fout,
 static void dumpType(Archive *fout, TypeInfo *tinfo);
 static void dumpBaseType(Archive *fout, TypeInfo *tinfo);
 static void dumpEnumType(Archive *fout, TypeInfo *tinfo);
+static void dumpDistinctType(Archive *fout, TypeInfo *tinfo);
 static void dumpDomain(Archive *fout, TypeInfo *tinfo);
 static void dumpCompositeType(Archive *fout, TypeInfo *tinfo);
 static void dumpShellType(Archive *fout, ShellTypeInfo *stinfo);
@@ -5755,6 +5756,8 @@ dumpType(Archive *fout, TypeInfo *tinfo)
     /* Dump out in proper style */
     if (tinfo->typtype == TYPTYPE_BASE)
         dumpBaseType(fout, tinfo);
+    else if (tinfo->typtype == TYPTYPE_DISTINCT)
+        dumpDistinctType(fout, tinfo);
     else if (tinfo->typtype == TYPTYPE_DOMAIN)
         dumpDomain(fout, tinfo);
     else if (tinfo->typtype == TYPTYPE_COMPOSITE)
@@ -6210,6 +6213,82 @@ dumpBaseType(Archive *fout, TypeInfo *ti
 }

 /*
+ * dumpDistinctType
+ *      writes out to fout the queries to recreate a user-defined distinct type
+ */
+static void
+dumpDistinctType(Archive *fout, TypeInfo *tinfo)
+{
+    PQExpBuffer q = createPQExpBuffer();
+    PQExpBuffer delq = createPQExpBuffer();
+    PQExpBuffer query = createPQExpBuffer();
+    PGresult   *res;
+    int            ntups;
+    char       *typdefn;
+
+    /* Set proper schema search path so type references list correctly */
+    selectSourceSchema(tinfo->dobj.namespace->dobj.name);
+
+    /* Fetch type specific details */
+    appendPQExpBuffer(query, "SELECT pg_catalog.format_type(typbasetype, typtypmod) as typdefn "
+                      "FROM pg_catalog.pg_type "
+                      "WHERE oid = '%u'::pg_catalog.oid",
+                      tinfo->dobj.catId.oid);
+
+    res = PQexec(g_conn, query->data);
+    check_sql_result(res, g_conn, query->data, PGRES_TUPLES_OK);
+
+    /* Expecting a single result only */
+    ntups = PQntuples(res);
+    if (ntups != 1)
+    {
+        write_msg(NULL, "query returned %d rows instead of one: %s\n",
+                  ntups, query->data);
+        exit_nicely();
+    }
+
+    typdefn = PQgetvalue(res, 0, PQfnumber(res, "typdefn"));
+
+    appendPQExpBuffer(q,
+                      "CREATE TYPE %s AS %s",
+                      fmtId(tinfo->dobj.name),
+                      typdefn);
+
+    PQclear(res);
+
+    appendPQExpBuffer(q, ";\n");
+
+    /*
+     * DROP must be fully qualified in case same name appears in pg_catalog
+     */
+    appendPQExpBuffer(delq, "DROP TYPE %s.",
+                      fmtId(tinfo->dobj.namespace->dobj.name));
+    appendPQExpBuffer(delq, "%s;\n",
+                      fmtId(tinfo->dobj.name));
+
+    ArchiveEntry(fout, tinfo->dobj.catId, tinfo->dobj.dumpId,
+                 tinfo->dobj.name,
+                 tinfo->dobj.namespace->dobj.name,
+                 NULL,
+                 tinfo->rolname, false,
+                 "TYPE", q->data, delq->data, NULL,
+                 tinfo->dobj.dependencies, tinfo->dobj.nDeps,
+                 NULL, NULL);
+
+    /* Dump Type Comments */
+    resetPQExpBuffer(q);
+
+    appendPQExpBuffer(q, "TYPE %s", fmtId(tinfo->dobj.name));
+    dumpComment(fout, q->data,
+                tinfo->dobj.namespace->dobj.name, tinfo->rolname,
+                tinfo->dobj.catId, 0, tinfo->dobj.dumpId);
+
+    destroyPQExpBuffer(q);
+    destroyPQExpBuffer(delq);
+    destroyPQExpBuffer(query);
+}
+
+/*
  * dumpDomain
  *      writes out to fout the queries to recreate a user-defined domain
  */
Index: src/include/catalog/pg_type.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/catalog/pg_type.h,v
retrieving revision 1.203
diff -u -3 -p -r1.203 pg_type.h
--- src/include/catalog/pg_type.h    21 Nov 2008 18:49:24 -0000    1.203
+++ src/include/catalog/pg_type.h    25 Nov 2008 10:13:18 -0000
@@ -60,7 +60,7 @@ CATALOG(pg_type,1247) BKI_BOOTSTRAP

     /*
      * typtype is 'b' for a base type, 'c' for a composite type (e.g., a
-     * table's rowtype), 'd' for a domain type, 'e' for an enum type, or 'p'
+     * table's rowtype), 'd' for a domain type, 'D' for a distinct type, 'e' for an enum type, or 'p'
      * for a pseudo-type.  (Use the TYPTYPE macros below.)
      *
      * If typtype is 'c', typrelid is the OID of the class' entry in pg_class.
@@ -632,6 +632,7 @@ DATA(insert OID = 3500 ( anyenum        PGNSP
 #define  TYPTYPE_BASE        'b' /* base type (ordinary scalar type) */
 #define  TYPTYPE_COMPOSITE    'c' /* composite (e.g., table's rowtype) */
 #define  TYPTYPE_DOMAIN        'd' /* domain over another type */
+#define  TYPTYPE_DISTINCT    'D' /* distinct type based on another type */
 #define  TYPTYPE_ENUM        'e' /* enumerated type */
 #define  TYPTYPE_PSEUDO        'p' /* pseudo-type */

Index: src/include/nodes/parsenodes.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/nodes/parsenodes.h,v
retrieving revision 1.379
diff -u -3 -p -r1.379 parsenodes.h
--- src/include/nodes/parsenodes.h    24 Nov 2008 08:46:04 -0000    1.379
+++ src/include/nodes/parsenodes.h    25 Nov 2008 10:13:18 -0000
@@ -1461,6 +1461,7 @@ typedef struct CreateDomainStmt
     List       *domainname;        /* qualified name (list of Value strings) */
     TypeName   *typename;        /* the base type */
     List       *constraints;    /* constraints (list of Constraint nodes) */
+    bool        distinct_type;    /* create distinct type rather than domain */
 } CreateDomainStmt;

 /* ----------------------
Index: src/include/utils/lsyscache.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/utils/lsyscache.h,v
retrieving revision 1.126
diff -u -3 -p -r1.126 lsyscache.h
--- src/include/utils/lsyscache.h    28 Sep 2008 19:51:40 -0000    1.126
+++ src/include/utils/lsyscache.h    25 Nov 2008 10:13:18 -0000
@@ -123,6 +123,7 @@ extern void getTypeBinaryOutputInfo(Oid
 extern Oid    get_typmodin(Oid typid);
 extern Oid    getBaseType(Oid typid);
 extern Oid    getBaseTypeAndTypmod(Oid typid, int32 *typmod);
+extern Oid    getDirectBaseType(Oid typid);
 extern int32 get_typavgwidth(Oid typid, int32 typmod);
 extern int32 get_attavgwidth(Oid relid, AttrNumber attnum);
 extern bool get_attstatsslot(HeapTuple statstuple,
Index: src/interfaces/ecpg/preproc/parse.pl
===================================================================
RCS file: /cvsroot/pgsql/src/interfaces/ecpg/preproc/parse.pl,v
retrieving revision 1.1
diff -u -3 -p -r1.1 parse.pl
--- src/interfaces/ecpg/preproc/parse.pl    14 Nov 2008 10:01:04 -0000    1.1
+++ src/interfaces/ecpg/preproc/parse.pl    25 Nov 2008 10:13:18 -0000
@@ -60,6 +60,7 @@ $replace_types{'Sconst'} = 'ignore';
 $replace_line{'fetch_direction'} = 'ignore';
 $replace_line{"opt_array_boundsopt_array_bounds'['Iconst']'"} = 'ignore';
 $replace_line{'col_name_keywordCHAR_P'} = 'ignore';
+$replace_line{'col_name_keywordENUM_P'} = 'ignore';
 $replace_line{'col_name_keywordINT_P'} = 'ignore';
 $replace_line{'col_name_keywordVALUES'} = 'ignore';
 $replace_line{'reserved_keywordTO'} = 'ignore';
Index: src/pl/plpgsql/src/pl_comp.c
===================================================================
RCS file: /cvsroot/pgsql/src/pl/plpgsql/src/pl_comp.c,v
retrieving revision 1.132
diff -u -3 -p -r1.132 pl_comp.c
--- src/pl/plpgsql/src/pl_comp.c    5 Nov 2008 00:07:53 -0000    1.132
+++ src/pl/plpgsql/src/pl_comp.c    25 Nov 2008 10:13:19 -0000
@@ -1725,6 +1725,7 @@ build_datatype(HeapTuple typeTup, int32
     switch (typeStruct->typtype)
     {
         case TYPTYPE_BASE:
+        case TYPTYPE_DISTINCT:
         case TYPTYPE_DOMAIN:
         case TYPTYPE_ENUM:
             typ->ttype = PLPGSQL_TTYPE_SCALAR;