doc: clarify that storage parameter values are optional

In a few cases, the documented syntax specified storage parameter values
as required.

Reported-by: galiev_mr@taximaxim.ru

Discussion: https://postgr.es/m/159283163235.684.4482737698910467437@wrigleys.postgresql.org

Backpatch-through: 9.5

doc/src/sgml/ref/alter_index.sgml

@@ -25,7 +25,7 @@ ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RENA
 ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET TABLESPACE <replaceable class="parameter">tablespace_name</replaceable>
 ALTER INDEX <replaceable class="parameter">name</replaceable> ATTACH PARTITION <replaceable class="parameter">index_name</replaceable>
 ALTER INDEX <replaceable class="parameter">name</replaceable> DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable>
-ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET ( <replaceable class="parameter">storage_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] )
+ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )
 ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RESET ( <replaceable class="parameter">storage_parameter</replaceable> [, ... ] )
 ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ALTER [ COLUMN ] <replaceable class="parameter">column_number</replaceable>
     SET STATISTICS <replaceable class="parameter">integer</replaceable>
@@ -113,7 +113,7 @@ ALTER INDEX ALL IN TABLESPACE <replaceable class="parameter">name</replaceable>
    </varlistentry>
 
    <varlistentry>
-    <term><literal>SET ( <replaceable class="parameter">storage_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] )</literal></term>
+    <term><literal>SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )</literal></term>
     <listitem>
      <para>
       This form changes one or more index-method-specific storage parameters

doc/src/sgml/ref/alter_materialized_view.sgml

@@ -42,7 +42,7 @@ ALTER MATERIALIZED VIEW ALL IN TABLESPACE <replaceable class="parameter">name</r
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     CLUSTER ON <replaceable class="parameter">index_name</replaceable>
     SET WITHOUT CLUSTER
-    SET ( <replaceable class="parameter">storage_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] )
+    SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )
     RESET ( <replaceable class="parameter">storage_parameter</replaceable> [, ... ] )
     OWNER TO { <replaceable class="parameter">new_owner</replaceable> | CURRENT_USER | SESSION_USER }
 </synopsis>

doc/src/sgml/ref/alter_table.sgml

@@ -76,7 +76,7 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     SET WITHOUT OIDS
     SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable>
     SET { LOGGED | UNLOGGED }
-    SET ( <replaceable class="parameter">storage_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] )
+    SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )
     RESET ( <replaceable class="parameter">storage_parameter</replaceable> [, ... ] )
     INHERIT <replaceable class="parameter">parent_table</replaceable>
     NO INHERIT <replaceable class="parameter">parent_table</replaceable>
@@ -702,7 +702,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
    </varlistentry>
 
    <varlistentry>
-    <term><literal>SET ( <replaceable class="parameter">storage_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] )</literal></term>
+    <term><literal>SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )</literal></term>
     <listitem>
      <para>
       This form changes one or more storage parameters for the table.  See

doc/src/sgml/ref/create_index.sgml

@@ -24,7 +24,7 @@ PostgreSQL documentation
 CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class="parameter">name</replaceable> ] ON [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ USING <replaceable class="parameter">method</replaceable> ]
     ( { <replaceable class="parameter">column_name</replaceable> | ( <replaceable class="parameter">expression</replaceable> ) } [ COLLATE <replaceable class="parameter">collation</replaceable> ] [ <replaceable class="parameter">opclass</replaceable> [ ( <replaceable class="parameter">opclass_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] ) ] ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] )
     [ INCLUDE ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ]
-    [ WITH ( <replaceable class="parameter">storage_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] ) ]
+    [ WITH ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] ) ]
     [ TABLESPACE <replaceable class="parameter">tablespace_name</replaceable> ]
     [ WHERE <replaceable class="parameter">predicate</replaceable> ]
 </synopsis>