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Commit05e27a9

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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'tget flattened into the main query because of the has_nullable_targetlistlimitation in prepjointree.c. That's triggered because pg_roles has '********'::text AS rolpasswordwhich isn't nullable, meaning it would produce wrong behavior ifreferenced above the outer join.Ultimately, the reason this is a problem is that the planner deals onlyin simple Vars while processing joins; it doesn't want to think aboutexpressions. I'm starting to think that it may be time to fix this,because I've run into several related restrictions lately, but it seemslike a nontrivial project.In the meantime, reducing the LEFT JOIN to pg_roles to a JOIN as perPeter's suggestion seems like the best short-term workaround.
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‎src/bin/psql/describe.c

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
*
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* Copyright (c) 2000-2005, PostgreSQL Global Development Group
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*
6-
* $PostgreSQL: pgsql/src/bin/psql/describe.c,v 1.131 2006/02/1203:22:19 momjian Exp $
6+
* $PostgreSQL: pgsql/src/bin/psql/describe.c,v 1.132 2006/02/1219:31:14 momjian Exp $
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*/
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#include"postgres_fe.h"
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#include"describe.h"
@@ -194,7 +194,7 @@ describeFunctions(const char *pattern, bool verbose)
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"\nFROM pg_catalog.pg_proc p"
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"\n LEFT JOIN pg_catalog.pg_namespace n ON n.oid = p.pronamespace"
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"\n LEFT JOIN pg_catalog.pg_language l ON l.oid = p.prolang"
197-
"\nLEFTJOIN pg_catalog.pg_roles r ON r.oid = p.proowner\n");
197+
"\n JOIN pg_catalog.pg_roles r ON r.oid = p.proowner\n");
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/*
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* we skip in/out funcs by excluding functions that take or return cstring
@@ -367,7 +367,7 @@ listAllDbs(bool verbose)
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_("Description"));
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appendPQExpBuffer(&buf,
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"\nFROM pg_catalog.pg_database d"
370-
"\nLEFTJOIN pg_catalog.pg_roles r ON d.datdba = r.oid\n"
370+
"\n JOIN pg_catalog.pg_roles r ON d.datdba = r.oid\n"
371371
"ORDER BY 1;");
372372

373373
res=PSQLexec(buf.data, false);
@@ -1485,7 +1485,7 @@ listTables(const char *tabtypes, const char *pattern, bool verbose)
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appendPQExpBuffer(&buf,
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"\nFROM pg_catalog.pg_class c"
1488-
"\nLEFTJOIN pg_catalog.pg_roles r ON r.oid = c.relowner"
1488+
"\n JOIN pg_catalog.pg_roles r ON r.oid = c.relowner"
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"\n LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace");
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if (showIndexes)
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appendPQExpBuffer(&buf,
@@ -1727,7 +1727,7 @@ listSchemas(const char *pattern, bool verbose)
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_("Access privileges"),_("Description"));
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17291729
appendPQExpBuffer(&buf,
1730-
"\nFROM pg_catalog.pg_namespace nLEFTJOIN pg_catalog.pg_roles r\n"
1730+
"\nFROM pg_catalog.pg_namespace n JOIN pg_catalog.pg_roles r\n"
17311731
" ON n.nspowner=r.oid\n"
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"WHERE(n.nspname !~ '^pg_temp_' OR\n"
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" n.nspname = (pg_catalog.current_schemas(true))[1])\n");/* temp schema is first */

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