Add comment that attributes.is_nullable was removed from SQL standard

We don't have to remove the column if no one is bothered, but it's
useful to comment on it in case someone looks for it in newer
standards versions.

diff --git a/src/backend/catalog/information_schema.sql b/src/backend/catalog/information_schema.sql
index 452a0ead44cab53c2dcc1fcc85b252ba00a404f2..81407a3a5eef591e7f8c7184e70de9deb60cc0fe 100644 (file)
--- a/src/backend/catalog/information_schema.sql
+++ b/src/backend/catalog/information_schema.sql
@@ -274,7 +274,7 @@ CREATE VIEW attributes AS
            CAST(pg_get_expr(ad.adbin, ad.adrelid) AS character_data) AS attribute_default,
            CAST(CASE WHEN a.attnotnull OR (t.typtype = 'd' AND t.typnotnull) THEN 'NO' ELSE 'YES' END
              AS yes_or_no)
-             AS is_nullable,
+             AS is_nullable, -- This column was apparently removed between SQL:2003 and SQL:2008.
 
            CAST(
              CASE WHEN t.typelem <> 0 AND t.typlen = -1 THEN 'ARRAY'