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

scrappy · scrappy · commit 27f56dd41e0d · 1996-08-24T20:56:42.000Z
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
diff --git a/src/backend/catalog/pg_attribute.h b/src/backend/catalog/pg_attribute.h
@@ -7,7 +7,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: pg_attribute.h,v 1.1.1.1.2.1 1996/08/21 04:23:32 scrappy Exp $
+ * $Id: pg_attribute.h,v 1.1.1.1.2.2 1996/08/24 20:56:42 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;
 
 /*
