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

20 files changed, 242 insertions, 273 deletions

diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
index 0152e3869ab..391a9b225db 100644
--- a/src/backend/catalog/namespace.c
+++ b/src/backend/catalog/namespace.c
@@ -1473,8 +1473,7 @@ FunctionIsVisible(Oid funcid)
  *		Given a possibly-qualified operator name and exact input datatypes,
  *		look up the operator.  Returns InvalidOid if not found.
  *
- * Pass oprleft = InvalidOid for a prefix op, oprright = InvalidOid for
- * a postfix op.
+ * Pass oprleft = InvalidOid for a prefix op.
  *
  * If the operator name is not schema-qualified, it is sought in the current
  * namespace search path.  If the name is schema-qualified and the given
@@ -1580,8 +1579,8 @@ OpernameGetOprid(List *names, Oid oprleft, Oid oprright)
  * namespace case, we arrange for entries in earlier namespaces to mask
  * identical entries in later namespaces.
  *
- * The returned items always have two args[] entries --- one or the other
- * will be InvalidOid for a prefix or postfix oprkind.  nargs is 2, too.
+ * The returned items always have two args[] entries --- the first will be
+ * InvalidOid for a prefix oprkind.  nargs is always 2, too.
  */
 FuncCandidateList
 OpernameGetCandidates(List *names, char oprkind, bool missing_schema_ok)
diff --git a/src/backend/catalog/pg_operator.c b/src/backend/catalog/pg_operator.c
index f7c07c9b5b8..904cb8ef820 100644
--- a/src/backend/catalog/pg_operator.c
+++ b/src/backend/catalog/pg_operator.c
@@ -245,7 +245,7 @@ OperatorShellMake(const char *operatorName,
 	values[Anum_pg_operator_oprname - 1] = NameGetDatum(&oname);
 	values[Anum_pg_operator_oprnamespace - 1] = ObjectIdGetDatum(operatorNamespace);
 	values[Anum_pg_operator_oprowner - 1] = ObjectIdGetDatum(GetUserId());
-	values[Anum_pg_operator_oprkind - 1] = CharGetDatum(leftTypeId ? (rightTypeId ? 'b' : 'r') : 'l');
+	values[Anum_pg_operator_oprkind - 1] = CharGetDatum(leftTypeId ? 'b' : 'l');
 	values[Anum_pg_operator_oprcanmerge - 1] = BoolGetDatum(false);
 	values[Anum_pg_operator_oprcanhash - 1] = BoolGetDatum(false);
 	values[Anum_pg_operator_oprleft - 1] = ObjectIdGetDatum(leftTypeId);
@@ -494,7 +494,7 @@ OperatorCreate(const char *operatorName,
 	values[Anum_pg_operator_oprname - 1] = NameGetDatum(&oname);
 	values[Anum_pg_operator_oprnamespace - 1] = ObjectIdGetDatum(operatorNamespace);
 	values[Anum_pg_operator_oprowner - 1] = ObjectIdGetDatum(GetUserId());
-	values[Anum_pg_operator_oprkind - 1] = CharGetDatum(leftTypeId ? (rightTypeId ? 'b' : 'r') : 'l');
+	values[Anum_pg_operator_oprkind - 1] = CharGetDatum(leftTypeId ? 'b' : 'l');
 	values[Anum_pg_operator_oprcanmerge - 1] = BoolGetDatum(canMerge);
 	values[Anum_pg_operator_oprcanhash - 1] = BoolGetDatum(canHash);
 	values[Anum_pg_operator_oprleft - 1] = ObjectIdGetDatum(leftTypeId);
diff --git a/src/backend/commands/operatorcmds.c b/src/backend/commands/operatorcmds.c
index bf23937849c..a791e99092d 100644
--- a/src/backend/commands/operatorcmds.c
+++ b/src/backend/commands/operatorcmds.c
@@ -168,10 +168,22 @@ DefineOperator(List *names, List *parameters)
 	if (typeName2)
 		typeId2 = typenameTypeId(NULL, typeName2);
 
+	/*
+	 * If only the right argument is missing, the user is likely trying to
+	 * create a postfix operator, so give them a hint about why that does not
+	 * work.  But if both arguments are missing, do not mention postfix
+	 * operators, as the user most likely simply neglected to mention the
+	 * arguments.
+	 */
 	if (!OidIsValid(typeId1) && !OidIsValid(typeId2))
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
-				 errmsg("at least one of leftarg or rightarg must be specified")));
+				 errmsg("operator argument types must be specified")));
+	if (!OidIsValid(typeId2))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
+				 errmsg("operator right argument type must be specified"),
+				 errdetail("Postfix operators are not supported.")));
 
 	if (typeName1)
 	{
diff --git a/src/backend/nodes/print.c b/src/backend/nodes/print.c
index 42476724d88..970a2d43840 100644
--- a/src/backend/nodes/print.c
+++ b/src/backend/nodes/print.c
@@ -394,7 +394,6 @@ print_expr(const Node *expr, const List *rtable)
 		}
 		else
 		{
-			/* we print prefix and postfix ops the same... */
 			printf("%s ", ((opname != NULL) ? opname : "(invalid operator)"));
 			print_expr(get_leftop((const Expr *) e), rtable);
 		}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 4558c02f6a6..b16ffb9bf7f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -741,10 +741,9 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %nonassoc	'<' '>' '=' LESS_EQUALS GREATER_EQUALS NOT_EQUALS
 %nonassoc	BETWEEN IN_P LIKE ILIKE SIMILAR NOT_LA
 %nonassoc	ESCAPE			/* ESCAPE must be just above LIKE/ILIKE/SIMILAR */
-%left		POSTFIXOP		/* dummy for postfix Op rules */
 /*
  * To support target_el without AS, we must give IDENT an explicit priority
- * between POSTFIXOP and Op.  We can safely assign the same priority to
+ * between ESCAPE and Op.  We can safely assign the same priority to
  * various unreserved keywords as needed to resolve ambiguities (this can't
  * have any bad effects since obviously the keywords will still behave the
  * same as if they weren't keywords).  We need to do this:
@@ -12993,8 +12992,6 @@ a_expr:		c_expr									{ $$ = $1; }
 				{ $$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, $3, @2); }
 			| qual_Op a_expr					%prec Op
 				{ $$ = (Node *) makeA_Expr(AEXPR_OP, $1, NULL, $2, @1); }
-			| a_expr qual_Op					%prec POSTFIXOP
-				{ $$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, NULL, @2); }
 
 			| a_expr AND a_expr
 				{ $$ = makeAndExpr($1, $3, @2); }
@@ -13408,8 +13405,6 @@ b_expr:		c_expr
 				{ $$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, $3, @2); }
 			| qual_Op b_expr					%prec Op
 				{ $$ = (Node *) makeA_Expr(AEXPR_OP, $1, NULL, $2, @1); }
-			| b_expr qual_Op					%prec POSTFIXOP
-				{ $$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, NULL, @2); }
 			| b_expr IS DISTINCT FROM b_expr		%prec IS
 				{
 					$$ = (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $5, @2);
@@ -14665,11 +14660,7 @@ target_el:	a_expr AS ColLabel
 				}
 			/*
 			 * We support omitting AS only for column labels that aren't
-			 * any known keyword.  There is an ambiguity against postfix
-			 * operators: is "a ! b" an infix expression, or a postfix
-			 * expression and a column label?  We prefer to resolve this
-			 * as an infix expression, which we accomplish by assigning
-			 * IDENT a precedence higher than POSTFIXOP.
+			 * any known keyword.
 			 */
 			| a_expr IDENT
 				{
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index f69976cc8c9..d24420c5831 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -57,7 +57,7 @@ bool		Transform_null_equals = false;
 #define PREC_GROUP_NOT_LIKE		9	/* NOT LIKE/ILIKE/SIMILAR */
 #define PREC_GROUP_NOT_BETWEEN	10	/* NOT BETWEEN */
 #define PREC_GROUP_NOT_IN		11	/* NOT IN */
-#define PREC_GROUP_POSTFIX_OP	12	/* generic postfix operators */
+#define PREC_GROUP_ANY_ALL		12	/* ANY/ALL */
 #define PREC_GROUP_INFIX_OP		13	/* generic infix operators */
 #define PREC_GROUP_PREFIX_OP	14	/* generic prefix operators */
 
@@ -71,7 +71,7 @@ bool		Transform_null_equals = false;
  * 4. LIKE ILIKE SIMILAR
  * 5. BETWEEN
  * 6. IN
- * 7. generic postfix Op
+ * 7. ANY ALL
  * 8. generic Op, including <= => <>
  * 9. generic prefix Op
  * 10. IS tests (NullTest, BooleanTest, etc)
@@ -1031,7 +1031,7 @@ transformAExprOpAny(ParseState *pstate, A_Expr *a)
 	Node	   *rexpr = a->rexpr;
 
 	if (operator_precedence_warning)
-		emit_precedence_warnings(pstate, PREC_GROUP_POSTFIX_OP,
+		emit_precedence_warnings(pstate, PREC_GROUP_ANY_ALL,
 								 strVal(llast(a->name)),
 								 lexpr, NULL,
 								 a->location);
@@ -1054,7 +1054,7 @@ transformAExprOpAll(ParseState *pstate, A_Expr *a)
 	Node	   *rexpr = a->rexpr;
 
 	if (operator_precedence_warning)
-		emit_precedence_warnings(pstate, PREC_GROUP_POSTFIX_OP,
+		emit_precedence_warnings(pstate, PREC_GROUP_ANY_ALL,
 								 strVal(llast(a->name)),
 								 lexpr, NULL,
 								 a->location);
@@ -2019,7 +2019,7 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
 										 sublink->testexpr, NULL,
 										 sublink->location);
 			else
-				emit_precedence_warnings(pstate, PREC_GROUP_POSTFIX_OP,
+				emit_precedence_warnings(pstate, PREC_GROUP_ANY_ALL,
 										 strVal(llast(sublink->operName)),
 										 sublink->testexpr, NULL,
 										 sublink->location);
@@ -3244,28 +3244,11 @@ operator_precedence_group(Node *node, const char **nodename)
 				group = PREC_GROUP_PREFIX_OP;
 			}
 		}
-		else if (aexpr->kind == AEXPR_OP &&
-				 aexpr->lexpr != NULL &&
-				 aexpr->rexpr == NULL)
-		{
-			/* postfix operator */
-			if (list_length(aexpr->name) == 1)
-			{
-				*nodename = strVal(linitial(aexpr->name));
-				group = PREC_GROUP_POSTFIX_OP;
-			}
-			else
-			{
-				/* schema-qualified operator syntax */
-				*nodename = "OPERATOR()";
-				group = PREC_GROUP_POSTFIX_OP;
-			}
-		}
 		else if (aexpr->kind == AEXPR_OP_ANY ||
 				 aexpr->kind == AEXPR_OP_ALL)
 		{
 			*nodename = strVal(llast(aexpr->name));
-			group = PREC_GROUP_POSTFIX_OP;
+			group = PREC_GROUP_ANY_ALL;
 		}
 		else if (aexpr->kind == AEXPR_DISTINCT ||
 				 aexpr->kind == AEXPR_NOT_DISTINCT)
@@ -3356,7 +3339,7 @@ operator_precedence_group(Node *node, const char **nodename)
 			else
 			{
 				*nodename = strVal(llast(s->operName));
-				group = PREC_GROUP_POSTFIX_OP;
+				group = PREC_GROUP_ANY_ALL;
 			}
 		}
 	}
@@ -3432,9 +3415,8 @@ emit_precedence_warnings(ParseState *pstate,
 	 * Complain if left child, which should be same or higher precedence
 	 * according to current rules, used to be lower precedence.
 	 *
-	 * Exception to precedence rules: if left child is IN or NOT IN or a
-	 * postfix operator, the grouping is syntactically forced regardless of
-	 * precedence.
+	 * Exception to precedence rules: if left child is IN or NOT IN the
+	 * grouping is syntactically forced regardless of precedence.
 	 */
 	cgroup = operator_precedence_group(lchild, &copname);
 	if (cgroup > 0)
@@ -3442,7 +3424,7 @@ emit_precedence_warnings(ParseState *pstate,
 		if (oldprecedence_l[cgroup] < oldprecedence_r[opgroup] &&
 			cgroup != PREC_GROUP_IN &&
 			cgroup != PREC_GROUP_NOT_IN &&
-			cgroup != PREC_GROUP_POSTFIX_OP &&
+			cgroup != PREC_GROUP_ANY_ALL &&
 			cgroup != PREC_GROUP_POSTFIX_IS)
 			ereport(WARNING,
 					(errmsg("operator precedence change: %s is now lower precedence than %s",
diff --git a/src/backend/parser/parse_oper.c b/src/backend/parser/parse_oper.c
index 2749974f638..6613a3a8f87 100644
--- a/src/backend/parser/parse_oper.c
+++ b/src/backend/parser/parse_oper.c
@@ -52,7 +52,7 @@ typedef struct OprCacheKey
 {
 	char		oprname[NAMEDATALEN];
 	Oid			left_arg;		/* Left input OID, or 0 if prefix op */
-	Oid			right_arg;		/* Right input OID, or 0 if postfix op */
+	Oid			right_arg;		/* Right input OID */
 	Oid			search_path[MAX_CACHED_PATH_LEN];
 } OprCacheKey;
 
@@ -88,8 +88,7 @@ static void InvalidateOprCacheCallBack(Datum arg, int cacheid, uint32 hashvalue)
  *		Given a possibly-qualified operator name and exact input datatypes,
  *		look up the operator.
  *
- * Pass oprleft = InvalidOid for a prefix op, oprright = InvalidOid for
- * a postfix op.
+ * Pass oprleft = InvalidOid for a prefix op.
  *
  * If the operator name is not schema-qualified, it is sought in the current
  * namespace search path.
@@ -115,10 +114,16 @@ LookupOperName(ParseState *pstate, List *opername, Oid oprleft, Oid oprright,
 
 		if (!OidIsValid(oprleft))
 			oprkind = 'l';
-		else if (!OidIsValid(oprright))
-			oprkind = 'r';
-		else
+		else if (OidIsValid(oprright))
 			oprkind = 'b';
+		else
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("postfix operators are not supported"),
+					 parser_errposition(pstate, location)));
+			oprkind = 0;		/* keep compiler quiet */
+		}
 
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_FUNCTION),
@@ -507,85 +512,6 @@ compatible_oper_opid(List *op, Oid arg1, Oid arg2, bool noError)
 }
 
 
-/* right_oper() -- search for a unary right operator (postfix operator)
- * Given operator name and type of arg, return oper struct.
- *
- * IMPORTANT: the returned operator (if any) is only promised to be
- * coercion-compatible with the input datatype.  Do not use this if
- * you need an exact- or binary-compatible match.
- *
- * If no matching operator found, return NULL if noError is true,
- * raise an error if it is false.  pstate and location are used only to report
- * the error position; pass NULL/-1 if not available.
- *
- * NOTE: on success, the returned object is a syscache entry.  The caller
- * must ReleaseSysCache() the entry when done with it.
- */
-Operator
-right_oper(ParseState *pstate, List *op, Oid arg, bool noError, int location)
-{
-	Oid			operOid;
-	OprCacheKey key;
-	bool		key_ok;
-	FuncDetailCode fdresult = FUNCDETAIL_NOTFOUND;
-	HeapTuple	tup = NULL;
-
-	/*
-	 * Try to find the mapping in the lookaside cache.
-	 */
-	key_ok = make_oper_cache_key(pstate, &key, op, arg, InvalidOid, location);
-
-	if (key_ok)
-	{
-		operOid = find_oper_cache_entry(&key);
-		if (OidIsValid(operOid))
-		{
-			tup = SearchSysCache1(OPEROID, ObjectIdGetDatum(operOid));
-			if (HeapTupleIsValid(tup))
-				return (Operator) tup;
-		}
-	}
-
-	/*
-	 * First try for an "exact" match.
-	 */
-	operOid = OpernameGetOprid(op, arg, InvalidOid);
-	if (!OidIsValid(operOid))
-	{
-		/*
-		 * Otherwise, search for the most suitable candidate.
-		 */
-		FuncCandidateList clist;
-
-		/* Get postfix operators of given name */
-		clist = OpernameGetCandidates(op, 'r', false);
-
-		/* No operators found? Then fail... */
-		if (clist != NULL)
-		{
-			/*
-			 * We must run oper_select_candidate even if only one candidate,
-			 * otherwise we may falsely return a non-type-compatible operator.
-			 */
-			fdresult = oper_select_candidate(1, &arg, clist, &operOid);
-		}
-	}
-
-	if (OidIsValid(operOid))
-		tup = SearchSysCache1(OPEROID, ObjectIdGetDatum(operOid));
-
-	if (HeapTupleIsValid(tup))
-	{
-		if (key_ok)
-			make_oper_cache_entry(&key, operOid);
-	}
-	else if (!noError)
-		op_error(pstate, op, 'r', arg, InvalidOid, fdresult, location);
-
-	return (Operator) tup;
-}
-
-
 /* left_oper() -- search for a unary left operator (prefix operator)
  * Given operator name and type of arg, return oper struct.
  *
@@ -696,8 +622,7 @@ op_signature_string(List *op, char oprkind, Oid arg1, Oid arg2)
 
 	appendStringInfoString(&argbuf, NameListToString(op));
 
-	if (oprkind != 'r')
-		appendStringInfo(&argbuf, " %s", format_type_be(arg2));
+	appendStringInfo(&argbuf, " %s", format_type_be(arg2));
 
 	return argbuf.data;			/* return palloc'd string buffer */
 }
@@ -758,17 +683,16 @@ make_op(ParseState *pstate, List *opname, Node *ltree, Node *rtree,
 	Oid			rettype;
 	OpExpr	   *result;
 
-	/* Select the operator */
+	/* Check it's not a postfix operator */
 	if (rtree == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("postfix operators are not supported")));
+
+	/* Select the operator */
+	if (ltree == NULL)
 	{
-		/* right operator */
-		ltypeId = exprType(ltree);
-		rtypeId = InvalidOid;
-		tup = right_oper(pstate, opname, ltypeId, false, location);
-	}
-	else if (ltree == NULL)
-	{
-		/* left operator */
+		/* prefix operator */
 		rtypeId = exprType(rtree);
 		ltypeId = InvalidOid;
 		tup = left_oper(pstate, opname, rtypeId, false, location);
@@ -795,17 +719,9 @@ make_op(ParseState *pstate, List *opname, Node *ltree, Node *rtree,
 				 parser_errposition(pstate, location)));
 
 	/* Do typecasting and build the expression tree */
-	if (rtree == NULL)
-	{
-		/* right operator */
-		args = list_make1(ltree);
-		actual_arg_types[0] = ltypeId;
-		declared_arg_types[0] = opform->oprleft;
-		nargs = 1;
-	}
-	else if (ltree == NULL)
+	if (ltree == NULL)
 	{
-		/* left operator */
+		/* prefix operator */
 		args = list_make1(rtree);
 		actual_arg_types[0] = rtypeId;
 		declared_arg_types[0] = opform->oprright;
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 60dd80c23c8..15877e37a60 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9198,35 +9198,14 @@ get_oper_expr(OpExpr *expr, deparse_context *context)
 	}
 	else
 	{
-		/* unary operator --- but which side? */
+		/* prefix operator */
 		Node	   *arg = (Node *) linitial(args);
-		HeapTuple	tp;
-		Form_pg_operator optup;
-
-		tp = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
-		if (!HeapTupleIsValid(tp))
-			elog(ERROR, "cache lookup failed for operator %u", opno);
-		optup = (Form_pg_operator) GETSTRUCT(tp);
-		switch (optup->oprkind)
-		{
-			case 'l':
-				appendStringInfo(buf, "%s ",
-								 generate_operator_name(opno,
-														InvalidOid,
-														exprType(arg)));
-				get_rule_expr_paren(arg, context, true, (Node *) expr);
-				break;
-			case 'r':
-				get_rule_expr_paren(arg, context, true, (Node *) expr);
-				appendStringInfo(buf, " %s",
-								 generate_operator_name(opno,
-														exprType(arg),
-														InvalidOid));
-				break;
-			default:
-				elog(ERROR, "bogus oprkind: %d", optup->oprkind);
-		}
-		ReleaseSysCache(tp);
+
+		appendStringInfo(buf, "%s ",
+						 generate_operator_name(opno,
+												InvalidOid,
+												exprType(arg)));
+		get_rule_expr_paren(arg, context, true, (Node *) expr);
 	}
 	if (!PRETTY_PAREN(context))
 		appendStringInfoChar(buf, ')');
@@ -11087,10 +11066,6 @@ generate_operator_name(Oid operid, Oid arg1, Oid arg2)
 			p_result = left_oper(NULL, list_make1(makeString(oprname)), arg2,
 								 true, -1);
 			break;
-		case 'r':
-			p_result = right_oper(NULL, list_make1(makeString(oprname)), arg1,
-								  true, -1);
-			break;
 		default:
 			elog(ERROR, "unrecognized oprkind: %d", operform->oprkind);
 			p_result = NULL;	/* keep compiler quiet */
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 320820165b7..dce6af09c9b 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -12650,6 +12650,11 @@ dumpOpr(Archive *fout, OprInfo *oprinfo)
 	oprcanmerge = PQgetvalue(res, 0, i_oprcanmerge);
 	oprcanhash = PQgetvalue(res, 0, i_oprcanhash);
 
+	/* In PG14 upwards postfix operator support does not exist anymore. */
+	if (strcmp(oprkind, "r") == 0)
+		pg_log_warning("postfix operators are not supported anymore (operator \"%s\")",
+					   oprcode);
+
 	oprregproc = convertRegProcReference(fout, oprcode);
 	if (oprregproc)
 	{
@@ -12662,7 +12667,8 @@ dumpOpr(Archive *fout, OprInfo *oprinfo)
 
 	/*
 	 * right unary means there's a left arg and left unary means there's a
-	 * right arg
+	 * right arg.  (Although the "r" case is dead code for PG14 and later,
+	 * continue to support it in case we're dumping from an old server.)
 	 */
 	if (strcmp(oprkind, "r") == 0 ||
 		strcmp(oprkind, "b") == 0)
diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index 00aef855dc0..2f7aa632c52 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -22,6 +22,7 @@ static void check_is_install_user(ClusterInfo *cluster);
 static void check_proper_datallowconn(ClusterInfo *cluster);
 static void check_for_prepared_transactions(ClusterInfo *cluster);
 static void check_for_isn_and_int8_passing_mismatch(ClusterInfo *cluster);
+static void check_for_user_defined_postfix_ops(ClusterInfo *cluster);
 static void check_for_tables_with_oids(ClusterInfo *cluster);
 static void check_for_reg_data_type_usage(ClusterInfo *cluster);
 static void check_for_jsonb_9_4_usage(ClusterInfo *cluster);
@@ -101,6 +102,13 @@ check_and_dump_old_cluster(bool live_check)
 	check_for_isn_and_int8_passing_mismatch(&old_cluster);
 
 	/*
+	 * Pre-PG 14 allowed user defined postfix operators, which are not
+	 * supported anymore.  Verify there are none, iff applicable.
+	 */
+	if (GET_MAJOR_VERSION(old_cluster.major_version) <= 1300)
+		check_for_user_defined_postfix_ops(&old_cluster);
+
+	/*
 	 * Pre-PG 12 allowed tables to be declared WITH OIDS, which is not
 	 * supported anymore. Verify there are none, iff applicable.
 	 */
@@ -896,6 +904,104 @@ check_for_isn_and_int8_passing_mismatch(ClusterInfo *cluster)
 		check_ok();
 }
 
+/*
+ * Verify that no user defined postfix operators exist.
+ */
+static void
+check_for_user_defined_postfix_ops(ClusterInfo *cluster)
+{
+	int			dbnum;
+	FILE	   *script = NULL;
+	bool		found = false;
+	char		output_path[MAXPGPATH];
+
+	prep_status("Checking for user-defined postfix operators");
+
+	snprintf(output_path, sizeof(output_path),
+			 "postfix_ops.txt");
+
+	/* Find any user defined postfix operators */
+	for (dbnum = 0; dbnum < cluster->dbarr.ndbs; dbnum++)
+	{
+		PGresult   *res;
+		bool		db_used = false;
+		int			ntups;
+		int			rowno;
+		int			i_oproid,
+					i_oprnsp,
+					i_oprname,
+					i_typnsp,
+					i_typname;
+		DbInfo	   *active_db = &cluster->dbarr.dbs[dbnum];
+		PGconn	   *conn = connectToServer(cluster, active_db->db_name);
+
+		/*
+		 * The query below hardcodes FirstNormalObjectId as 16384 rather than
+		 * interpolating that C #define into the query because, if that
+		 * #define is ever changed, the cutoff we want to use is the value
+		 * used by pre-version 14 servers, not that of some future version.
+		 */
+		res = executeQueryOrDie(conn,
+								"SELECT o.oid AS oproid, "
+								"       n.nspname AS oprnsp, "
+								"       o.oprname, "
+								"       tn.nspname AS typnsp, "
+								"       t.typname "
+								"FROM pg_catalog.pg_operator o, "
+								"     pg_catalog.pg_namespace n, "
+								"     pg_catalog.pg_type t, "
+								"     pg_catalog.pg_namespace tn "
+								"WHERE o.oprnamespace = n.oid AND "
+								"      o.oprleft = t.oid AND "
+								"      t.typnamespace = tn.oid AND "
+								"      o.oprright = 0 AND "
+								"      o.oid >= 16384");
+		ntups = PQntuples(res);
+		i_oproid = PQfnumber(res, "oproid");
+		i_oprnsp = PQfnumber(res, "oprnsp");
+		i_oprname = PQfnumber(res, "oprname");
+		i_typnsp = PQfnumber(res, "typnsp");
+		i_typname = PQfnumber(res, "typname");
+		for (rowno = 0; rowno < ntups; rowno++)
+		{
+			found = true;
+			if (script == NULL &&
+				(script = fopen_priv(output_path, "w")) == NULL)
+				pg_fatal("could not open file \"%s\": %s\n",
+						 output_path, strerror(errno));
+			if (!db_used)
+			{
+				fprintf(script, "In database: %s\n", active_db->db_name);
+				db_used = true;
+			}
+			fprintf(script, "  (oid=%s) %s.%s (%s.%s, NONE)\n",
+					PQgetvalue(res, rowno, i_oproid),
+					PQgetvalue(res, rowno, i_oprnsp),
+					PQgetvalue(res, rowno, i_oprname),
+					PQgetvalue(res, rowno, i_typnsp),
+					PQgetvalue(res, rowno, i_typname));
+		}
+
+		PQclear(res);
+
+		PQfinish(conn);
+	}
+
+	if (script)
+		fclose(script);
+
+	if (found)
+	{
+		pg_log(PG_REPORT, "fatal\n");
+		pg_fatal("Your installation contains user-defined postfix operators, which are not\n"
+				 "supported anymore.  Consider dropping the postfix operators and replacing\n"
+				 "them with prefix operators or function calls.\n"
+				 "A list of user-defined postfix operators is in the file:\n"
+				 "    %s\n\n", output_path);
+	}
+	else
+		check_ok();
+}
 
 /*
  * Verify that no tables are declared WITH OIDS.
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index f22d907b1f9..58de433fd30 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -799,6 +799,10 @@ describeOperators(const char *pattern, bool verbose, bool showSystem)
 	 * anyway, for now, because (1) third-party modules may still be following
 	 * the old convention, and (2) we'd need to do it anyway when talking to a
 	 * pre-9.1 server.
+	 *
+	 * The support for postfix operators in this query is dead code as of
+	 * Postgres 14, but we need to keep it for as long as we support talking
+	 * to pre-v14 servers.
 	 */
 
 	printfPQExpBuffer(&buf,
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 35893599708..365552635b8 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202009171
+#define CATALOG_VERSION_NO	202009172
 
 #endif
diff --git a/src/include/catalog/pg_operator.h b/src/include/catalog/pg_operator.h
index 1daa2638520..62a7dbf23f6 100644
--- a/src/include/catalog/pg_operator.h
+++ b/src/include/catalog/pg_operator.h
@@ -41,7 +41,7 @@ CATALOG(pg_operator,2617,OperatorRelationId)
 	/* operator owner */
 	Oid			oprowner BKI_DEFAULT(PGUID);
 
-	/* 'l', 'r', or 'b' */
+	/* 'l' for prefix or 'b' for infix */
 	char		oprkind BKI_DEFAULT(b);
 
 	/* can be used in merge join? */
@@ -50,10 +50,10 @@ CATALOG(pg_operator,2617,OperatorRelationId)
 	/* can be used in hash join? */
 	bool		oprcanhash BKI_DEFAULT(f);
 
-	/* left arg type, or 0 if 'l' oprkind */
+	/* left arg type, or 0 if prefix operator */
 	Oid			oprleft BKI_LOOKUP(pg_type);
 
-	/* right arg type, or 0 if 'r' oprkind */
+	/* right arg type */
 	Oid			oprright BKI_LOOKUP(pg_type);
 
 	/* result datatype */
diff --git a/src/include/parser/parse_oper.h b/src/include/parser/parse_oper.h
index bcd861e43ac..09695a2765c 100644
--- a/src/include/parser/parse_oper.h
+++ b/src/include/parser/parse_oper.h
@@ -31,8 +31,6 @@ extern Oid	LookupOperWithArgs(ObjectWithArgs *oper, bool noError);
 /* NB: the selected operator may require coercion of the input types! */
 extern Operator oper(ParseState *pstate, List *op, Oid arg1, Oid arg2,
 					 bool noError, int location);
-extern Operator right_oper(ParseState *pstate, List *op, Oid arg,
-						   bool noError, int location);
 extern Operator left_oper(ParseState *pstate, List *op, Oid arg,
 						  bool noError, int location);
 
diff --git a/src/test/regress/expected/create_operator.out b/src/test/regress/expected/create_operator.out
index 9e4d4e93fb7..53032775914 100644
--- a/src/test/regress/expected/create_operator.out
+++ b/src/test/regress/expected/create_operator.out
@@ -15,17 +15,15 @@ CREATE OPERATOR <% (
    negator = >=%
 );
 CREATE OPERATOR @#@ (
-   rightarg = int8,		-- left unary
-   procedure = factorial
-);
-CREATE OPERATOR #@# (
-   leftarg = int8,		-- right unary
+   rightarg = int8,		-- prefix
    procedure = factorial
 );
 CREATE OPERATOR #%# (
-   leftarg = int8,		-- right unary
+   leftarg = int8,		-- fail, postfix is no longer supported
    procedure = factorial
 );
+ERROR:  operator right argument type must be specified
+DETAIL:  Postfix operators are not supported.
 -- Test operator created above
 SELECT point '(1,2)' <% widget '(0,0,3)' AS t,
        point '(1,2)' <% widget '(0,0,1)' AS f;
@@ -35,11 +33,22 @@ SELECT point '(1,2)' <% widget '(0,0,3)' AS t,
 (1 row)
 
 -- Test comments
-COMMENT ON OPERATOR ###### (int4, NONE) IS 'bad right unary';
-ERROR:  operator does not exist: integer ######
--- => is disallowed now
+COMMENT ON OPERATOR ###### (NONE, int4) IS 'bad prefix';
+ERROR:  operator does not exist: ###### integer
+COMMENT ON OPERATOR ###### (int4, NONE) IS 'bad postfix';
+ERROR:  postfix operators are not supported
+COMMENT ON OPERATOR ###### (int4, int8) IS 'bad infix';
+ERROR:  operator does not exist: integer ###### bigint
+-- Check that DROP on a nonexistent op behaves sanely, too
+DROP OPERATOR ###### (NONE, int4);
+ERROR:  operator does not exist: ###### integer
+DROP OPERATOR ###### (int4, NONE);
+ERROR:  postfix operators are not supported
+DROP OPERATOR ###### (int4, int8);
+ERROR:  operator does not exist: integer ###### bigint
+-- => is disallowed as an operator name now
 CREATE OPERATOR => (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial
 );
 ERROR:  syntax error at or near "=>"
@@ -49,15 +58,20 @@ LINE 1: CREATE OPERATOR => (
 -- (=> is tested elsewhere)
 -- this is legal because ! is not allowed in sql ops
 CREATE OPERATOR !=- (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial
 );
-SELECT 2 !=-;
+SELECT !=- 10;
  ?column? 
 ----------
-        2
+  3628800
 (1 row)
 
+-- postfix operators don't work anymore
+SELECT 10 !=-;
+ERROR:  syntax error at or near ";"
+LINE 1: SELECT 10 !=-;
+                     ^
 -- make sure lexer returns != as <> even in edge cases
 SELECT 2 !=/**/ 1, 2 !=/**/ 2;
  ?column? | ?column? 
@@ -127,7 +141,7 @@ GRANT USAGE ON SCHEMA schema_op1 TO PUBLIC;
 REVOKE USAGE ON SCHEMA schema_op1 FROM regress_rol_op1;
 SET ROLE regress_rol_op1;
 CREATE OPERATOR schema_op1.#*# (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial
 );
 ERROR:  permission denied for schema schema_op1
@@ -167,19 +181,19 @@ CREATE OPERATOR === (
 ROLLBACK;
 -- Should fail. Invalid attribute
 CREATE OPERATOR #@%# (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial,
    invalid_att = int8
 );
 WARNING:  operator attribute "invalid_att" not recognized
--- Should fail. At least leftarg or rightarg should be mandatorily specified
+-- Should fail. At least rightarg should be mandatorily specified
 CREATE OPERATOR #@%# (
    procedure = factorial
 );
-ERROR:  at least one of leftarg or rightarg must be specified
+ERROR:  operator argument types must be specified
 -- Should fail. Procedure should be mandatorily specified
 CREATE OPERATOR #@%# (
-   leftarg = int8
+   rightarg = int8
 );
 ERROR:  operator function must be specified
 -- Should fail. CREATE OPERATOR requires USAGE on TYPE
diff --git a/src/test/regress/expected/opr_sanity.out b/src/test/regress/expected/opr_sanity.out
index 1b3c146e4cc..7825a765cd7 100644
--- a/src/test/regress/expected/opr_sanity.out
+++ b/src/test/regress/expected/opr_sanity.out
@@ -1066,7 +1066,7 @@ WHERE condefault AND
 -- Look for illegal values in pg_operator fields.
 SELECT p1.oid, p1.oprname
 FROM pg_operator as p1
-WHERE (p1.oprkind != 'b' AND p1.oprkind != 'l' AND p1.oprkind != 'r') OR
+WHERE (p1.oprkind != 'b' AND p1.oprkind != 'l') OR
     p1.oprresult = 0 OR p1.oprcode = 0;
  oid | oprname 
 -----+---------
@@ -1077,8 +1077,7 @@ SELECT p1.oid, p1.oprname
 FROM pg_operator as p1
 WHERE (p1.oprleft = 0 and p1.oprkind != 'l') OR
     (p1.oprleft != 0 and p1.oprkind = 'l') OR
-    (p1.oprright = 0 and p1.oprkind != 'r') OR
-    (p1.oprright != 0 and p1.oprkind = 'r');
+    p1.oprright = 0;
  oid | oprname 
 -----+---------
 (0 rows)
@@ -1285,18 +1284,6 @@ WHERE p1.oprcode = p2.oid AND
 -----+---------+-----+---------
 (0 rows)
 
-SELECT p1.oid, p1.oprname, p2.oid, p2.proname
-FROM pg_operator AS p1, pg_proc AS p2
-WHERE p1.oprcode = p2.oid AND
-    p1.oprkind = 'r' AND
-    (p2.pronargs != 1
-     OR NOT binary_coercible(p2.prorettype, p1.oprresult)
-     OR NOT binary_coercible(p1.oprleft, p2.proargtypes[0])
-     OR p1.oprright != 0);
- oid | oprname | oid | proname 
------+---------+-----+---------
-(0 rows)
-
 -- If the operator is mergejoinable or hashjoinable, its underlying function
 -- should not be volatile.
 SELECT p1.oid, p1.oprname, p2.oid, p2.proname
diff --git a/src/test/regress/sql/create_operator.sql b/src/test/regress/sql/create_operator.sql
index c32da8c066a..4ff2c0ff216 100644
--- a/src/test/regress/sql/create_operator.sql
+++ b/src/test/regress/sql/create_operator.sql
@@ -18,17 +18,12 @@ CREATE OPERATOR <% (
 );
 
 CREATE OPERATOR @#@ (
-   rightarg = int8,		-- left unary
-   procedure = factorial
-);
-
-CREATE OPERATOR #@# (
-   leftarg = int8,		-- right unary
+   rightarg = int8,		-- prefix
    procedure = factorial
 );
 
 CREATE OPERATOR #%# (
-   leftarg = int8,		-- right unary
+   leftarg = int8,		-- fail, postfix is no longer supported
    procedure = factorial
 );
 
@@ -37,11 +32,18 @@ SELECT point '(1,2)' <% widget '(0,0,3)' AS t,
        point '(1,2)' <% widget '(0,0,1)' AS f;
 
 -- Test comments
-COMMENT ON OPERATOR ###### (int4, NONE) IS 'bad right unary';
+COMMENT ON OPERATOR ###### (NONE, int4) IS 'bad prefix';
+COMMENT ON OPERATOR ###### (int4, NONE) IS 'bad postfix';
+COMMENT ON OPERATOR ###### (int4, int8) IS 'bad infix';
+
+-- Check that DROP on a nonexistent op behaves sanely, too
+DROP OPERATOR ###### (NONE, int4);
+DROP OPERATOR ###### (int4, NONE);
+DROP OPERATOR ###### (int4, int8);
 
--- => is disallowed now
+-- => is disallowed as an operator name now
 CREATE OPERATOR => (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial
 );
 
@@ -50,10 +52,12 @@ CREATE OPERATOR => (
 
 -- this is legal because ! is not allowed in sql ops
 CREATE OPERATOR !=- (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial
 );
-SELECT 2 !=-;
+SELECT !=- 10;
+-- postfix operators don't work anymore
+SELECT 10 !=-;
 -- make sure lexer returns != as <> even in edge cases
 SELECT 2 !=/**/ 1, 2 !=/**/ 2;
 SELECT 2 !=-- comment to be removed by psql
@@ -84,7 +88,7 @@ GRANT USAGE ON SCHEMA schema_op1 TO PUBLIC;
 REVOKE USAGE ON SCHEMA schema_op1 FROM regress_rol_op1;
 SET ROLE regress_rol_op1;
 CREATE OPERATOR schema_op1.#*# (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial
 );
 ROLLBACK;
@@ -128,19 +132,19 @@ ROLLBACK;
 
 -- Should fail. Invalid attribute
 CREATE OPERATOR #@%# (
-   leftarg = int8,		-- right unary
+   rightarg = int8,
    procedure = factorial,
    invalid_att = int8
 );
 
--- Should fail. At least leftarg or rightarg should be mandatorily specified
+-- Should fail. At least rightarg should be mandatorily specified
 CREATE OPERATOR #@%# (
    procedure = factorial
 );
 
 -- Should fail. Procedure should be mandatorily specified
 CREATE OPERATOR #@%# (
-   leftarg = int8
+   rightarg = int8
 );
 
 -- Should fail. CREATE OPERATOR requires USAGE on TYPE
diff --git a/src/test/regress/sql/opr_sanity.sql b/src/test/regress/sql/opr_sanity.sql
index 7a9180b0815..307aab1deb7 100644
--- a/src/test/regress/sql/opr_sanity.sql
+++ b/src/test/regress/sql/opr_sanity.sql
@@ -571,7 +571,7 @@ WHERE condefault AND
 
 SELECT p1.oid, p1.oprname
 FROM pg_operator as p1
-WHERE (p1.oprkind != 'b' AND p1.oprkind != 'l' AND p1.oprkind != 'r') OR
+WHERE (p1.oprkind != 'b' AND p1.oprkind != 'l') OR
     p1.oprresult = 0 OR p1.oprcode = 0;
 
 -- Look for missing or unwanted operand types
@@ -580,8 +580,7 @@ SELECT p1.oid, p1.oprname
 FROM pg_operator as p1
 WHERE (p1.oprleft = 0 and p1.oprkind != 'l') OR
     (p1.oprleft != 0 and p1.oprkind = 'l') OR
-    (p1.oprright = 0 and p1.oprkind != 'r') OR
-    (p1.oprright != 0 and p1.oprkind = 'r');
+    p1.oprright = 0;
 
 -- Look for conflicting operator definitions (same names and input datatypes).
 
@@ -715,15 +714,6 @@ WHERE p1.oprcode = p2.oid AND
      OR NOT binary_coercible(p1.oprright, p2.proargtypes[0])
      OR p1.oprleft != 0);
 
-SELECT p1.oid, p1.oprname, p2.oid, p2.proname
-FROM pg_operator AS p1, pg_proc AS p2
-WHERE p1.oprcode = p2.oid AND
-    p1.oprkind = 'r' AND
-    (p2.pronargs != 1
-     OR NOT binary_coercible(p2.prorettype, p1.oprresult)
-     OR NOT binary_coercible(p1.oprleft, p2.proargtypes[0])
-     OR p1.oprright != 0);
-
 -- If the operator is mergejoinable or hashjoinable, its underlying function
 -- should not be volatile.
 
diff --git a/src/tutorial/complex.source b/src/tutorial/complex.source
index 03559267016..d849ec0d4b7 100644
--- a/src/tutorial/complex.source
+++ b/src/tutorial/complex.source
@@ -111,7 +111,7 @@ CREATE FUNCTION complex_add(complex, complex)
    LANGUAGE C IMMUTABLE STRICT;
 
 -- we can now define the operator. We show a binary operator here but you
--- can also define unary operators by omitting either of leftarg or rightarg.
+-- can also define a prefix operator by omitting the leftarg.
 CREATE OPERATOR + (
    leftarg = complex,
    rightarg = complex,
diff --git a/src/tutorial/syscat.source b/src/tutorial/syscat.source
index 3a1767f97be..8a04d6a961f 100644
--- a/src/tutorial/syscat.source
+++ b/src/tutorial/syscat.source
@@ -96,36 +96,22 @@ SELECT n.nspname, r.rolname, format_type(t.oid, null) as typname
 
 
 --
--- lists all left unary operators
+-- lists all prefix operators
 --
-SELECT n.nspname, o.oprname AS left_unary,
+SELECT n.nspname, o.oprname AS prefix_op,
        format_type(right_type.oid, null) AS operand,
        format_type(result.oid, null) AS return_type
   FROM pg_namespace n, pg_operator o,
        pg_type right_type, pg_type result
   WHERE o.oprnamespace = n.oid
-    and o.oprkind = 'l'           -- left unary
+    and o.oprkind = 'l'           -- prefix ("left unary")
     and o.oprright = right_type.oid
     and o.oprresult = result.oid
   ORDER BY nspname, operand;
 
 
 --
--- lists all right unary operators
---
-SELECT n.nspname, o.oprname AS right_unary,
-       format_type(left_type.oid, null) AS operand,
-       format_type(result.oid, null) AS return_type
-  FROM pg_namespace n, pg_operator o,
-       pg_type left_type, pg_type result
-  WHERE o.oprnamespace = n.oid
-    and o.oprkind = 'r'          -- right unary
-    and o.oprleft = left_type.oid
-    and o.oprresult = result.oid
-  ORDER BY nspname, operand;
-
---
--- lists all binary operators
+-- lists all infix operators
 --
 SELECT n.nspname, o.oprname AS binary_op,
        format_type(left_type.oid, null) AS left_opr,
@@ -134,7 +120,7 @@ SELECT n.nspname, o.oprname AS binary_op,
   FROM pg_namespace n, pg_operator o, pg_type left_type,
        pg_type right_type, pg_type result
   WHERE o.oprnamespace = n.oid
-    and o.oprkind = 'b'         -- binary
+    and o.oprkind = 'b'         -- infix ("binary")
     and o.oprleft = left_type.oid
     and o.oprright = right_type.oid
     and o.oprresult = result.oid