This patch for Versions 1 and 2 corrects the following bug:

In a catalog class that has a "name" type attribute, UPDATEing of an
instance of that class may destroy all of the attributes of that
instance that are stored as or after the "name" attribute.

This is caused by the alignment value of the "name" type being set to
"double" in Class pg_type, but "integer" in Class pg_attribute.
Postgres constructs a tuple using double alignment, but interprets it
using integer alignment.

The fix is to change the alignment to integer in pg_type.

Note that this corrects the problem for new Postgres systems.  Existing
databases already contain the error and it can't easily be repaired because
this very bug prevents updating the class that contains it.

--
Bryan Henderson                                    Phone 408-227-6803
San Jose, California

Author: scrappy

src/backend/catalog/pg_attribute.h

@@ -7,7 +7,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: pg_attribute.h,v 1.2 1996/08/21 04:25:47 scrappy Exp $
+ * $Id: pg_attribute.h,v 1.3 1996/08/24 20:56:13 scrappy Exp $
  *
  * NOTES
  *    the genbki.sh script reads this file and generates .bki
@@ -44,13 +44,19 @@ CATALOG(pg_attribute) BOOTSTRAP {
     Oid  	attrelid;      
     NameData  	attname;
     Oid  	atttypid;
+      /* atttypid is the OID of the instance in Catalog Class pg_type that
+         defines the data type of this attribute (e.g. int4).  Information in
+         that instance is redundant with the attlen, attbyval, and attalign
+         attributes of this instance, so they had better match or Postgres
+         will fail.
+         */
     Oid  	attdefrel;
     int4  	attnvals;
     Oid  	atttyparg;	/* type arg for arrays/spquel/procs */
     int2 	attlen;
-      /* attlen is the number of bytes we use to represent the value 
-         of this attribute, e.g. 4 for an int4.  But for a variable length 
-         attribute, attlen is -1.
+      /* attlen is a copy of the typlen field from pg_type for this
+         attribute.  See atttypid above.  See struct TypeTupleFormData for
+         definition.
          */
     int2  	attnum;
       /* attnum is the "attribute number" for the attribute:  A 
@@ -68,6 +74,10 @@ CATALOG(pg_attribute) BOOTSTRAP {
          */
     int2 	attbound;
     bool  	attbyval;
+      /* attbyval is a copy of the typbyval field from pg_type for this
+         attribute.  See atttypid above.  See struct TypeTupleFormData for
+         definition.
+         */
     bool 	attcanindex;
     Oid 	attproc;	/* spquel? */
     int4	attnelems;
@@ -80,7 +90,11 @@ CATALOG(pg_attribute) BOOTSTRAP {
          walking process.  
          */
     bool        attisset;
-    char	attalign;  /* alignment (c=char, s=short, i=int, d=double) */
+    char	attalign; 
+      /* attalign is a copy of the typalign field from pg_type for this
+         attribute.  See atttypid above.  See struct TypeTupleFormData for
+         definition.
+         */
 } FormData_pg_attribute;
 
 /*

src/backend/catalog/pg_type.h

@@ -7,7 +7,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: pg_type.h,v 1.3 1996/07/19 05:21:28 scrappy Exp $
+ * $Id: pg_type.h,v 1.4 1996/08/24 20:56:16 scrappy Exp $
  *
  * NOTES
  *    the genbki.sh script reads this file and generates .bki
@@ -30,14 +30,34 @@
 /* ----------------
  *	pg_type definition.  cpp turns this into
  *	typedef struct FormData_pg_type
+ *
+ *      Some of the values in a pg_type instance are copied into 
+ *      pg_attribute intances.  Some parts of Postgres use the pg_type copy,
+ *      while others use the pg_attribute copy, so they must match.
+ *      See struct FormData_pg_attribute for details.
  * ----------------
  */
 CATALOG(pg_type) BOOTSTRAP {
     NameData 	typname;
     Oid  	typowner;
     int2  	typlen;
+      /* typlen is the number of bytes we use to represent a value of
+         this type, e.g. 4 for an int4.  But for a variable length
+         attribute, typlen is -1.  
+         */
     int2  	typprtlen;
     bool  	typbyval;
+      /* typbyval determines whether internal Postgres routines pass a value
+         of this type by value or by reference.  Postgres uses a 4 byte 
+         area for passing class data, so if the value is not 1, 2,
+         or 4 bytes long, Postgres does not have the option of passing by
+         value and ignores typbyval.  
+
+         (I don't understand why this attribute exists.  The above description
+         may be an oversimplification.  Also, there appear to be bugs in which
+         Postgres doesn't ignore typbyval when it should, but I'm 
+         afraid to change them until I see proof of damage. -BRYANH 96.08).
+         */
     char  	typtype;
     bool  	typisdefined;
     char	typdelim;
@@ -47,7 +67,23 @@ CATALOG(pg_type) BOOTSTRAP {
     regproc  	typoutput;
     regproc  	typreceive;
     regproc  	typsend;
-    char	typalign;	/* alignment (c=char, s=short, i=int, d=double) */
+    char	typalign;
+      /* typalign is the alignment required when storing a value of this
+         type.  It applies to storage on disk as well as most representations
+         of the value inside Postgres.  When multiple values are stored 
+         consecutively, such as in the representation of a complete tuple
+         on disk, padding is inserted before a datum of this type so that it
+         begins on the specified boundary.  The alignment reference is the 
+         beginning of the first datum in the sequence.
+
+         'c' = 1 byte alignment.
+         's' = 2 byte alignment.
+         'i' = 4 byte alignment.
+         'd' = 8 byte alignment.
+
+         (This might actually be flexible depending on machine architecture,
+         but I doubt it - BRYANH 96.08).
+         */
     text     	typdefault;	/* VARIABLE LENGTH FIELD */
 } TypeTupleFormData;
 
@@ -87,6 +123,11 @@ typedef TypeTupleFormData	*TypeTupleForm;
 
 /* keep the following ordered by OID so that later changes can be made easier*/
 
+/* Make sure the typlen, typbyval, and typalign values here match the initial
+   values for attlen, attbyval, and attalign in both places in pg_attribute.h 
+   for every instance.
+*/
+
 /* OIDS 1 - 99 */
 DATA(insert OID = 16 (  bool       PGUID  1   1 t b t \054 0   0 boolin boolout boolin boolout c _null_ ));
 
@@ -95,7 +136,7 @@ DATA(insert OID = 16 (  bool       PGUID  1   1 t b t \054 0   0 boolin boolout
 DATA(insert OID = 17 (  bytea      PGUID -1  -1 f b t \054 0  18 byteain byteaout byteain byteaout i _null_ ));
 DATA(insert OID = 18 (  char       PGUID  1   1 t b t \054 0   0 charin charout charin charout c _null_ ));
 
-DATA(insert OID = 19 (  name      PGUID NAMEDATALEN NAMEDATALEN  f b t \054 0  18 namein nameout namein nameout d _null_ ));
+DATA(insert OID = 19 (  name      PGUID NAMEDATALEN NAMEDATALEN  f b t \054 0  18 namein nameout namein nameout i _null_ ));
 DATA(insert OID = 20 (  char16     PGUID 16  16 f b t \054 0  18 char16in char16out char16in char16out i _null_ ));
 /*DATA(insert OID = 20 (  dt         PGUID  4  10 t b t \054 0   0 dtin dtout dtin dtout i _null_ )); */
 DATA(insert OID = 21 (  int2       PGUID  2   5 t b t \054 0   0 int2in int2out int2in int2out s _null_ ));