Improve error messages about mismatching relkind

Most error messages about a relkind that was not supported or
appropriate for the command was of the pattern

    "relation \"%s\" is not a table, foreign table, or materialized view"

This style can become verbose and tedious to maintain.  Moreover, it's
not very helpful: If I'm trying to create a comment on a TOAST table,
which is not supported, then the information that I could have created
a comment on a materialized view is pointless.

Instead, write the primary error message shorter and saying more
directly that what was attempted is not possible.  Then, in the detail
message, explain that the operation is not supported for the relkind
the object was.  To simplify that, add a new function
errdetail_relkind_not_supported() that does this.

In passing, make use of RELKIND_HAS_STORAGE() where appropriate,
instead of listing out the relkinds individually.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/flat/dc35a398-37d0-75ce-07ea-1dd71d98f8ec@2ndquadrant.com

2 files changed, 53 insertions, 27 deletions

diff --git a/contrib/pg_visibility/expected/pg_visibility.out b/contrib/pg_visibility/expected/pg_visibility.out
index 315633bfea6..9de54db2a29 100644
--- a/contrib/pg_visibility/expected/pg_visibility.out
+++ b/contrib/pg_visibility/expected/pg_visibility.out
@@ -41,66 +41,91 @@ ROLLBACK;
 create table test_partitioned (a int) partition by list (a);
 -- these should all fail
 select pg_visibility('test_partitioned', 0);
-ERROR:  "test_partitioned" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_partitioned" is of wrong relation kind
+DETAIL:  This operation is not supported for partitioned tables.
 select pg_visibility_map('test_partitioned');
-ERROR:  "test_partitioned" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_partitioned" is of wrong relation kind
+DETAIL:  This operation is not supported for partitioned tables.
 select pg_visibility_map_summary('test_partitioned');
-ERROR:  "test_partitioned" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_partitioned" is of wrong relation kind
+DETAIL:  This operation is not supported for partitioned tables.
 select pg_check_frozen('test_partitioned');
-ERROR:  "test_partitioned" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_partitioned" is of wrong relation kind
+DETAIL:  This operation is not supported for partitioned tables.
 select pg_truncate_visibility_map('test_partitioned');
-ERROR:  "test_partitioned" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_partitioned" is of wrong relation kind
+DETAIL:  This operation is not supported for partitioned tables.
 create table test_partition partition of test_partitioned for values in (1);
 create index test_index on test_partition (a);
 -- indexes do not, so these all fail
 select pg_visibility('test_index', 0);
-ERROR:  "test_index" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_index" is of wrong relation kind
+DETAIL:  This operation is not supported for indexes.
 select pg_visibility_map('test_index');
-ERROR:  "test_index" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_index" is of wrong relation kind
+DETAIL:  This operation is not supported for indexes.
 select pg_visibility_map_summary('test_index');
-ERROR:  "test_index" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_index" is of wrong relation kind
+DETAIL:  This operation is not supported for indexes.
 select pg_check_frozen('test_index');
-ERROR:  "test_index" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_index" is of wrong relation kind
+DETAIL:  This operation is not supported for indexes.
 select pg_truncate_visibility_map('test_index');
-ERROR:  "test_index" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_index" is of wrong relation kind
+DETAIL:  This operation is not supported for indexes.
 create view test_view as select 1;
 -- views do not have VMs, so these all fail
 select pg_visibility('test_view', 0);
-ERROR:  "test_view" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_view" is of wrong relation kind
+DETAIL:  This operation is not supported for views.
 select pg_visibility_map('test_view');
-ERROR:  "test_view" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_view" is of wrong relation kind
+DETAIL:  This operation is not supported for views.
 select pg_visibility_map_summary('test_view');
-ERROR:  "test_view" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_view" is of wrong relation kind
+DETAIL:  This operation is not supported for views.
 select pg_check_frozen('test_view');
-ERROR:  "test_view" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_view" is of wrong relation kind
+DETAIL:  This operation is not supported for views.
 select pg_truncate_visibility_map('test_view');
-ERROR:  "test_view" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_view" is of wrong relation kind
+DETAIL:  This operation is not supported for views.
 create sequence test_sequence;
 -- sequences do not have VMs, so these all fail
 select pg_visibility('test_sequence', 0);
-ERROR:  "test_sequence" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_sequence" is of wrong relation kind
+DETAIL:  This operation is not supported for sequences.
 select pg_visibility_map('test_sequence');
-ERROR:  "test_sequence" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_sequence" is of wrong relation kind
+DETAIL:  This operation is not supported for sequences.
 select pg_visibility_map_summary('test_sequence');
-ERROR:  "test_sequence" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_sequence" is of wrong relation kind
+DETAIL:  This operation is not supported for sequences.
 select pg_check_frozen('test_sequence');
-ERROR:  "test_sequence" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_sequence" is of wrong relation kind
+DETAIL:  This operation is not supported for sequences.
 select pg_truncate_visibility_map('test_sequence');
-ERROR:  "test_sequence" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_sequence" is of wrong relation kind
+DETAIL:  This operation is not supported for sequences.
 create foreign data wrapper dummy;
 create server dummy_server foreign data wrapper dummy;
 create foreign table test_foreign_table () server dummy_server;
 -- foreign tables do not have VMs, so these all fail
 select pg_visibility('test_foreign_table', 0);
-ERROR:  "test_foreign_table" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_foreign_table" is of wrong relation kind
+DETAIL:  This operation is not supported for foreign tables.
 select pg_visibility_map('test_foreign_table');
-ERROR:  "test_foreign_table" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_foreign_table" is of wrong relation kind
+DETAIL:  This operation is not supported for foreign tables.
 select pg_visibility_map_summary('test_foreign_table');
-ERROR:  "test_foreign_table" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_foreign_table" is of wrong relation kind
+DETAIL:  This operation is not supported for foreign tables.
 select pg_check_frozen('test_foreign_table');
-ERROR:  "test_foreign_table" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_foreign_table" is of wrong relation kind
+DETAIL:  This operation is not supported for foreign tables.
 select pg_truncate_visibility_map('test_foreign_table');
-ERROR:  "test_foreign_table" is not a table, materialized view, or TOAST table
+ERROR:  relation "test_foreign_table" is of wrong relation kind
+DETAIL:  This operation is not supported for foreign tables.
 -- check some of the allowed relkinds
 create table regular_table (a int, b text);
 alter table regular_table alter column b set storage external;
diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c
index dd0c124e625..c6d983183db 100644
--- a/contrib/pg_visibility/pg_visibility.c
+++ b/contrib/pg_visibility/pg_visibility.c
@@ -781,6 +781,7 @@ check_relation_relkind(Relation rel)
 		rel->rd_rel->relkind != RELKIND_TOASTVALUE)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is not a table, materialized view, or TOAST table",
-						RelationGetRelationName(rel))));
+				 errmsg("relation \"%s\" is of wrong relation kind",
+						RelationGetRelationName(rel)),
+				 errdetail_relkind_not_supported(rel->rd_rel->relkind)));
 }