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

1 files changed, 7 insertions, 32 deletions

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 */