From 05e27a9c20d4cd9f605e8601ca6b04be9056113e Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Sun, 12 Feb 2006 19:31:14 +0000
Subject: [PATCH] Remove LEFT part of JOIN to pg_roles because of optimizer
limitation:
> True, but they're not being used where you'd expect. This seems to be
> something to do with the fact that it's not pg_authid which is being
> accessed, but rather the view pg_roles.
I looked into this and it seems the problem is that the view doesn't
get flattened into the main query because of the has_nullable_targetlist
limitation in prepjointree.c. That's triggered because pg_roles has
'********'::text AS rolpassword
which isn't nullable, meaning it would produce wrong behavior if
referenced above the outer join.
Ultimately, the reason this is a problem is that the planner deals only
in simple Vars while processing joins; it doesn't want to think about
expressions. I'm starting to think that it may be time to fix this,
because I've run into several related restrictions lately, but it seems
like a nontrivial project.
In the meantime, reducing the LEFT JOIN to pg_roles to a JOIN as per
Peter's suggestion seems like the best short-term workaround.
---
src/bin/psql/describe.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 17ca722f307..1653ae2bdaf 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -3,7 +3,7 @@
*
* Copyright (c) 2000-2005, PostgreSQL Global Development Group
*
- * $PostgreSQL: pgsql/src/bin/psql/describe.c,v 1.131 2006/02/12 03:22:19 momjian Exp $
+ * $PostgreSQL: pgsql/src/bin/psql/describe.c,v 1.132 2006/02/12 19:31:14 momjian Exp $
*/
#include "postgres_fe.h"
#include "describe.h"
@@ -194,7 +194,7 @@ describeFunctions(const char *pattern, bool verbose)
"\nFROM pg_catalog.pg_proc p"
"\n LEFT JOIN pg_catalog.pg_namespace n ON n.oid = p.pronamespace"
"\n LEFT JOIN pg_catalog.pg_language l ON l.oid = p.prolang"
- "\n LEFT JOIN pg_catalog.pg_roles r ON r.oid = p.proowner\n");
+ "\n JOIN pg_catalog.pg_roles r ON r.oid = p.proowner\n");
/*
* we skip in/out funcs by excluding functions that take or return cstring
@@ -367,7 +367,7 @@ listAllDbs(bool verbose)
_("Description"));
appendPQExpBuffer(&buf,
"\nFROM pg_catalog.pg_database d"
- "\n LEFT JOIN pg_catalog.pg_roles r ON d.datdba = r.oid\n"
+ "\n JOIN pg_catalog.pg_roles r ON d.datdba = r.oid\n"
"ORDER BY 1;");
res = PSQLexec(buf.data, false);
@@ -1485,7 +1485,7 @@ listTables(const char *tabtypes, const char *pattern, bool verbose)
appendPQExpBuffer(&buf,
"\nFROM pg_catalog.pg_class c"
- "\n LEFT JOIN pg_catalog.pg_roles r ON r.oid = c.relowner"
+ "\n JOIN pg_catalog.pg_roles r ON r.oid = c.relowner"
"\n LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace");
if (showIndexes)
appendPQExpBuffer(&buf,
@@ -1727,7 +1727,7 @@ listSchemas(const char *pattern, bool verbose)
_("Access privileges"), _("Description"));
appendPQExpBuffer(&buf,
- "\nFROM pg_catalog.pg_namespace n LEFT JOIN pg_catalog.pg_roles r\n"
+ "\nFROM pg_catalog.pg_namespace n JOIN pg_catalog.pg_roles r\n"
" ON n.nspowner=r.oid\n"
"WHERE (n.nspname !~ '^pg_temp_' OR\n"
" n.nspname = (pg_catalog.current_schemas(true))[1])\n"); /* temp schema is first */
--
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