On 21/08/2018 17:38, Peter Eisentraut wrote:
> On 20/08/2018 15:14, Tom Lane wrote:
>> I agree this is all moot as long as there's no pad bytes. What I'm
>> trying to figure out is if we need to put in place some provisions
>> to prevent there from being pad bytes at the end of any catalog struct.
>> According to what Andres is saying, it seems like we do (at least for
>> ones with varlena fields).
>
> Yes, I think there could be a problem. I took a brief look through the
> catalogs, and while there are plenty of catalogs with trailing padding,
> finding that in combination with trailing varlena fields that might
> legitimately be all null in practice might require a closer look.
Looking into this a bit more, a few catalogs could use some
BKI_FORCE_NOT_NULL settings, which then avoids the described situation.
See attached patch.
That leaves pg_constraint and pg_event_trigger where you can construct
legitimate tuples where the fixed portion has trailing padding and the
variable fields can all be null.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
From db8534ddab46560ea870b3197db22a9b3b2ab551 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pete...@gmx.net>
Date: Fri, 24 Aug 2018 16:33:55 +0200
Subject: [PATCH] Add some not null constraints to catalogs
Use BKI_FORCE_NOT_NULL on some catalog field declarations that are never
null (according to the source code that accesses them).
---
src/include/catalog/pg_attrdef.h | 4 ++--
src/include/catalog/pg_default_acl.h | 2 +-
src/include/catalog/pg_policy.h | 2 +-
src/include/catalog/pg_rewrite.h | 4 ++--
4 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/src/include/catalog/pg_attrdef.h b/src/include/catalog/pg_attrdef.h
index 68800ffd8e..e4a37ec326 100644
--- a/src/include/catalog/pg_attrdef.h
+++ b/src/include/catalog/pg_attrdef.h
@@ -32,8 +32,8 @@ CATALOG(pg_attrdef,2604,AttrDefaultRelationId)
int16 adnum; /* attnum of attribute */
#ifdef CATALOG_VARLEN /* variable-length fields start here */
- pg_node_tree adbin; /* nodeToString representation
of default */
- text adsrc; /* human-readable
representation of default */
+ pg_node_tree adbin BKI_FORCE_NOT_NULL; /* nodeToString
representation of default */
+ text adsrc BKI_FORCE_NOT_NULL; /*
human-readable representation of default */
#endif
} FormData_pg_attrdef;
diff --git a/src/include/catalog/pg_default_acl.h
b/src/include/catalog/pg_default_acl.h
index d0410f5586..aee49fdb6d 100644
--- a/src/include/catalog/pg_default_acl.h
+++ b/src/include/catalog/pg_default_acl.h
@@ -34,7 +34,7 @@ CATALOG(pg_default_acl,826,DefaultAclRelationId)
char defaclobjtype; /* see DEFACLOBJ_xxx constants below */
#ifdef CATALOG_VARLEN /* variable-length fields start here */
- aclitem defaclacl[1]; /* permissions to add at CREATE time */
+ aclitem defaclacl[1] BKI_FORCE_NOT_NULL; /* permissions
to add at CREATE time */
#endif
} FormData_pg_default_acl;
diff --git a/src/include/catalog/pg_policy.h b/src/include/catalog/pg_policy.h
index ea3765b1cb..0dd9c50e53 100644
--- a/src/include/catalog/pg_policy.h
+++ b/src/include/catalog/pg_policy.h
@@ -34,7 +34,7 @@ CATALOG(pg_policy,3256,PolicyRelationId)
bool polpermissive; /* restrictive or permissive policy */
#ifdef CATALOG_VARLEN
- Oid polroles[1]; /* Roles associated with
policy, not-NULL */
+ Oid polroles[1] BKI_FORCE_NOT_NULL; /* Roles
associated with policy */
pg_node_tree polqual; /* Policy quals. */
pg_node_tree polwithcheck; /* WITH CHECK quals. */
#endif
diff --git a/src/include/catalog/pg_rewrite.h b/src/include/catalog/pg_rewrite.h
index a385445884..0e50b87926 100644
--- a/src/include/catalog/pg_rewrite.h
+++ b/src/include/catalog/pg_rewrite.h
@@ -38,8 +38,8 @@ CATALOG(pg_rewrite,2618,RewriteRelationId)
bool is_instead;
#ifdef CATALOG_VARLEN /* variable-length fields start here */
- pg_node_tree ev_qual;
- pg_node_tree ev_action;
+ pg_node_tree ev_qual BKI_FORCE_NOT_NULL;
+ pg_node_tree ev_action BKI_FORCE_NOT_NULL;
#endif
} FormData_pg_rewrite;
--
2.18.0
