Remove support for postfix (right-unary) operators.

This feature has been a thorn in our sides for a long time, causing
many grammatical ambiguity problems.  It doesn't seem worth the
pain to continue to support it, so remove it.

There are some follow-on improvements we can make in the grammar,
but this commit only removes the bare minimum number of productions,
plus assorted backend support code.

Note that pg_dump and psql continue to have full support, since
they may be used against older servers.  However, pg_dump warns
about postfix operators.  There is also a check in pg_upgrade.

Documentation-wise, I (tgl) largely removed the "left unary"
terminology in favor of saying "prefix operator", which is
a more standard and IMO less confusing term.

I included a catversion bump, although no initial catalog data
changes here, to mark the boundary at which oprkind = 'r'
stopped being valid in pg_operator.

Mark Dilger, based on work by myself and Robert Haas;
review by John Naylor

Discussion: https://postgr.es/m/38ca86db-42ab-9b48-2902-337a0d6b8311@2ndquadrant.com

11 files changed, 32 insertions, 54 deletions

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 508bea3bc64..7e99928d0c1 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -5159,8 +5159,8 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
        <structfield>oprkind</structfield> <type>char</type>
       </para>
       <para>
-       <literal>b</literal> = infix (<quote>both</quote>), <literal>l</literal> = prefix
-       (<quote>left</quote>), <literal>r</literal> = postfix (<quote>right</quote>)
+       <literal>b</literal> = infix operator (<quote>both</quote>),
+       or <literal>l</literal> = prefix operator (<quote>left</quote>)
       </para></entry>
      </row>
 
@@ -5188,7 +5188,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
        (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
       </para>
       <para>
-       Type of the left operand
+       Type of the left operand (0 if none)
       </para></entry>
      </row>
 
@@ -5266,7 +5266,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
   </table>
 
   <para>
-   Unused column contain zeroes. For example, <structfield>oprleft</structfield>
+   Unused columns contain zeroes. For example, <structfield>oprleft</structfield>
    is zero for a prefix operator.
   </para>
 
diff --git a/doc/src/sgml/ref/alter_extension.sgml b/doc/src/sgml/ref/alter_extension.sgml
index a2d405d6cdf..c819c7bb4e3 100644
--- a/doc/src/sgml/ref/alter_extension.sgml
+++ b/doc/src/sgml/ref/alter_extension.sgml
@@ -251,7 +251,7 @@ ALTER EXTENSION <replaceable class="parameter">name</replaceable> DROP <replacea
       <para>
        The data type(s) of the operator's arguments (optionally
        schema-qualified).  Write <literal>NONE</literal> for the missing argument
-       of a prefix or postfix operator.
+       of a prefix operator.
       </para>
      </listitem>
     </varlistentry>
diff --git a/doc/src/sgml/ref/alter_operator.sgml b/doc/src/sgml/ref/alter_operator.sgml
index ac35f229a0c..ad90c137f14 100644
--- a/doc/src/sgml/ref/alter_operator.sgml
+++ b/doc/src/sgml/ref/alter_operator.sgml
@@ -21,13 +21,13 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</replaceable> | NONE } , { <replaceable>right_type</replaceable> | NONE } )
+ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</replaceable> | NONE } , <replaceable>right_type</replaceable> )
     OWNER TO { <replaceable>new_owner</replaceable> | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
 
-ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</replaceable> | NONE } , { <replaceable>right_type</replaceable> | NONE } )
+ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</replaceable> | NONE } , <replaceable>right_type</replaceable> )
     SET SCHEMA <replaceable>new_schema</replaceable>
 
-ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</replaceable> | NONE } , { <replaceable>right_type</replaceable> | NONE } )
+ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</replaceable> | NONE } , <replaceable>right_type</replaceable> )
     SET ( {  RESTRICT = { <replaceable class="parameter">res_proc</replaceable> | NONE }
            | JOIN = { <replaceable class="parameter">join_proc</replaceable> | NONE }
          } [, ... ] )
@@ -79,8 +79,7 @@ ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</repla
     <term><replaceable class="parameter">right_type</replaceable></term>
     <listitem>
      <para>
-      The data type of the operator's right operand; write
-      <literal>NONE</literal> if the operator has no right operand.
+      The data type of the operator's right operand.
      </para>
     </listitem>
    </varlistentry>
diff --git a/doc/src/sgml/ref/alter_opfamily.sgml b/doc/src/sgml/ref/alter_opfamily.sgml
index 59d5bf10700..b3b5d61a852 100644
--- a/doc/src/sgml/ref/alter_opfamily.sgml
+++ b/doc/src/sgml/ref/alter_opfamily.sgml
@@ -141,7 +141,7 @@ ALTER OPERATOR FAMILY <replaceable>name</replaceable> USING <replaceable class="
      <para>
       In an <literal>OPERATOR</literal> clause,
       the operand data type(s) of the operator, or <literal>NONE</literal> to
-      signify a left-unary or right-unary operator.  Unlike the comparable
+      signify a prefix operator.  Unlike the comparable
       syntax in <command>CREATE OPERATOR CLASS</command>, the operand data types
       must always be specified.
      </para>
diff --git a/doc/src/sgml/ref/comment.sgml b/doc/src/sgml/ref/comment.sgml
index fd7492a2556..6e8ced3eaf1 100644
--- a/doc/src/sgml/ref/comment.sgml
+++ b/doc/src/sgml/ref/comment.sgml
@@ -224,7 +224,7 @@ COMMENT ON
      <para>
       The data type(s) of the operator's arguments (optionally
       schema-qualified).  Write <literal>NONE</literal> for the missing argument
-      of a prefix or postfix operator.
+      of a prefix operator.
      </para>
     </listitem>
    </varlistentry>
diff --git a/doc/src/sgml/ref/create_opclass.sgml b/doc/src/sgml/ref/create_opclass.sgml
index f42fb6494c6..2d75a1c0b0d 100644
--- a/doc/src/sgml/ref/create_opclass.sgml
+++ b/doc/src/sgml/ref/create_opclass.sgml
@@ -161,7 +161,7 @@ CREATE OPERATOR CLASS <replaceable class="parameter">name</replaceable> [ DEFAUL
      <para>
       In an <literal>OPERATOR</literal> clause,
       the operand data type(s) of the operator, or <literal>NONE</literal> to
-      signify a left-unary or right-unary operator.  The operand data
+      signify a prefix operator.  The operand data
       types can be omitted in the normal case where they are the same
       as the operator class's data type.
      </para>
diff --git a/doc/src/sgml/ref/create_operator.sgml b/doc/src/sgml/ref/create_operator.sgml
index 66c34e0072f..9462bc1e8ca 100644
--- a/doc/src/sgml/ref/create_operator.sgml
+++ b/doc/src/sgml/ref/create_operator.sgml
@@ -86,20 +86,9 @@ CREATE OPERATOR <replaceable>name</replaceable> (
   </para>
 
   <para>
-   At least one of <literal>LEFTARG</literal> and <literal>RIGHTARG</literal> must be defined.  For
-   binary operators, both must be defined. For right unary
-   operators, only <literal>LEFTARG</literal> should be defined, while for left
-   unary operators only <literal>RIGHTARG</literal> should be defined.
-  </para>
-
-  <note>
-   <para>
-    Right unary, also called postfix, operators are deprecated and will be
-    removed in <productname>PostgreSQL</productname> version 14.
-   </para>
-  </note>
-
-  <para>
+   For binary operators, both <literal>LEFTARG</literal> and
+   <literal>RIGHTARG</literal> must be defined.  For prefix operators only
+   <literal>RIGHTARG</literal> should be defined.
    The <replaceable class="parameter">function_name</replaceable>
    function must have been previously defined using <command>CREATE
    FUNCTION</command> and must be defined to accept the correct number
@@ -160,7 +149,7 @@ CREATE OPERATOR <replaceable>name</replaceable> (
       <listitem>
        <para>
         The data type of the operator's left operand, if any.
-        This option would be omitted for a left-unary operator.
+        This option would be omitted for a prefix operator.
        </para>
       </listitem>
      </varlistentry>
@@ -169,8 +158,7 @@ CREATE OPERATOR <replaceable>name</replaceable> (
       <term><replaceable class="parameter">right_type</replaceable></term>
       <listitem>
        <para>
-        The data type of the operator's right operand, if any.
-        This option would be omitted for a right-unary operator.
+        The data type of the operator's right operand.
        </para>
       </listitem>
      </varlistentry>
diff --git a/doc/src/sgml/ref/drop_operator.sgml b/doc/src/sgml/ref/drop_operator.sgml
index 2dff050ecf2..7bcdd082ae7 100644
--- a/doc/src/sgml/ref/drop_operator.sgml
+++ b/doc/src/sgml/ref/drop_operator.sgml
@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP OPERATOR [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ( { <replaceable class="parameter">left_type</replaceable> | NONE } , { <replaceable class="parameter">right_type</replaceable> | NONE } ) [, ...] [ CASCADE | RESTRICT ]
+DROP OPERATOR [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ( { <replaceable class="parameter">left_type</replaceable> | NONE } , <replaceable class="parameter">right_type</replaceable> ) [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -73,8 +73,7 @@ DROP OPERATOR [ IF EXISTS ] <replaceable class="parameter">name</replaceable> (
     <term><replaceable class="parameter">right_type</replaceable></term>
     <listitem>
      <para>
-      The data type of the operator's right operand; write
-      <literal>NONE</literal> if the operator has no right operand.
+      The data type of the operator's right operand.
      </para>
     </listitem>
    </varlistentry>
@@ -113,7 +112,7 @@ DROP OPERATOR ^ (integer, integer);
   </para>
 
   <para>
-   Remove the left unary bitwise complement operator
+   Remove the bitwise-complement prefix operator
    <literal>~b</literal> for type <type>bit</type>:
 <programlisting>
 DROP OPERATOR ~ (none, bit);
@@ -121,16 +120,9 @@ DROP OPERATOR ~ (none, bit);
   </para>
 
   <para>
-   Remove the right unary factorial operator <literal>x!</literal>
-   for type <type>bigint</type>:
-<programlisting>
-DROP OPERATOR ! (bigint, none);
-</programlisting></para>
-
-  <para>
    Remove multiple operators in one command:
 <programlisting>
-DROP OPERATOR ~ (none, bit), ! (bigint, none);
+DROP OPERATOR ~ (none, bit), ^ (integer, integer);
 </programlisting></para>
  </refsect1>
 
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index b0ae5d2e127..3fdd87823e0 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -836,7 +836,7 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )
    <para>
     When working with non-SQL-standard operator names, you will usually
     need to separate adjacent operators with spaces to avoid ambiguity.
-    For example, if you have defined a left unary operator named <literal>@</literal>,
+    For example, if you have defined a prefix operator named <literal>@</literal>,
     you cannot write <literal>X*@Y</literal>; you must write
     <literal>X* @Y</literal> to ensure that
     <productname>PostgreSQL</productname> reads it as two operator names
@@ -1444,11 +1444,10 @@ $1.somecolumn
    </indexterm>
 
    <para>
-    There are three possible syntaxes for an operator invocation:
+    There are two possible syntaxes for an operator invocation:
     <simplelist>
      <member><replaceable>expression</replaceable> <replaceable>operator</replaceable> <replaceable>expression</replaceable> (binary infix operator)</member>
      <member><replaceable>operator</replaceable> <replaceable>expression</replaceable> (unary prefix operator)</member>
-     <member><replaceable>expression</replaceable> <replaceable>operator</replaceable> (unary postfix operator)</member>
     </simplelist>
     where the <replaceable>operator</replaceable> token follows the syntax
     rules of <xref linkend="sql-syntax-operators"/>, or is one of the
diff --git a/doc/src/sgml/typeconv.sgml b/doc/src/sgml/typeconv.sgml
index 98662fc91fb..cfeb851a507 100644
--- a/doc/src/sgml/typeconv.sgml
+++ b/doc/src/sgml/typeconv.sgml
@@ -97,8 +97,8 @@ Operators
 <listitem>
 <para>
 <productname>PostgreSQL</productname> allows expressions with
-prefix and postfix unary (one-argument) operators,
-as well as binary (two-argument) operators.  Like functions, operators can
+prefix (one-argument) operators,
+as well as infix (two-argument) operators.  Like functions, operators can
 be overloaded, so the same problem of selecting the right operator
 exists.
 </para>
@@ -266,7 +266,7 @@ create objects.  In such situations, cast arguments to force an exact match.
 <para>
 If one argument of a binary operator invocation is of the <type>unknown</type> type,
 then assume it is the same type as the other argument for this check.
-Invocations involving two <type>unknown</type> inputs, or a unary operator
+Invocations involving two <type>unknown</type> inputs, or a prefix operator
 with an <type>unknown</type> input, will never find a match at this step.
 </para>
 </step>
diff --git a/doc/src/sgml/xoper.sgml b/doc/src/sgml/xoper.sgml
index 56b08491c96..98f4c5c4aa4 100644
--- a/doc/src/sgml/xoper.sgml
+++ b/doc/src/sgml/xoper.sgml
@@ -20,8 +20,8 @@
   </para>
 
   <para>
-   <productname>PostgreSQL</productname> supports left unary, right
-   unary, and binary operators.  Operators can be
+   <productname>PostgreSQL</productname> supports prefix
+   and infix operators.  Operators can be
    overloaded;<indexterm><primary>overloading</primary><secondary>operators</secondary></indexterm>
    that is, the same operator name can be used for different operators
    that have different numbers and types of operands.  When a query is
@@ -64,9 +64,9 @@ SELECT (a + b) AS c FROM test_complex;
   </para>
 
   <para>
-   We've shown how to create a binary operator here.  To create unary
-   operators, just omit one of <literal>leftarg</literal> (for left unary) or
-   <literal>rightarg</literal> (for right unary).  The <literal>function</literal>
+   We've shown how to create a binary operator here.  To create a prefix
+   operator, just omit the <literal>leftarg</literal>.
+   The <literal>function</literal>
    clause and the argument clauses are the only required items in
    <command>CREATE OPERATOR</command>.  The <literal>commutator</literal>
    clause shown in the example is an optional hint to the query
@@ -202,7 +202,7 @@ SELECT (a + b) AS c FROM test_complex;
    <para>
     Unlike commutators, a pair of unary operators could validly be marked
     as each other's negators; that would mean (A x) equals NOT (B x)
-    for all x, or the equivalent for right unary operators.
+    for all x.
    </para>
 
    <para>