doc: Fix column_name parameter in ALTER MATERIALIZED VIEW

Parameter column_name must be an existing column because ALTER
MATERIALIZED VIEW cannot add new columns.  The old description was
likely copied from ALTER TABLE.

Author: Erik Wienhold
Discussion: https://postgr.es/m/6880ca53-7961-4eeb-86d5-6bd05fc2027e@ewie.name
Backpatch-through: 12

diff --git a/doc/src/sgml/ref/alter_materialized_view.sgml b/doc/src/sgml/ref/alter_materialized_view.sgml
index c6a132de068230d0ad6e56db825d8f0d6169efbf..862921fd41d47801c7d664ebf7336178b2f3ac25 100644 (file)
--- a/doc/src/sgml/ref/alter_materialized_view.sgml
+++ b/doc/src/sgml/ref/alter_materialized_view.sgml
@@ -98,7 +98,7 @@ ALTER MATERIALIZED VIEW ALL IN TABLESPACE name
      column_name
      
       
-       Name of a new or existing column.
+       Name of an existing column.