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, 6 insertions, 13 deletions

diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index ad37a742213..2d44df19fee 100644
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -2706,7 +2706,6 @@ deparseOpExpr(OpExpr *node, deparse_expr_cxt *context)
 	HeapTuple	tuple;
 	Form_pg_operator form;
 	char		oprkind;
-	ListCell   *arg;
 
 	/* Retrieve information about the operator from system catalog. */
 	tuple = SearchSysCache1(OPEROID, ObjectIdGetDatum(node->opno));
@@ -2716,18 +2715,16 @@ deparseOpExpr(OpExpr *node, deparse_expr_cxt *context)
 	oprkind = form->oprkind;
 
 	/* Sanity check. */
-	Assert((oprkind == 'r' && list_length(node->args) == 1) ||
-		   (oprkind == 'l' && list_length(node->args) == 1) ||
+	Assert((oprkind == 'l' && list_length(node->args) == 1) ||
 		   (oprkind == 'b' && list_length(node->args) == 2));
 
 	/* Always parenthesize the expression. */
 	appendStringInfoChar(buf, '(');
 
-	/* Deparse left operand. */
-	if (oprkind == 'r' || oprkind == 'b')
+	/* Deparse left operand, if any. */
+	if (oprkind == 'b')
 	{
-		arg = list_head(node->args);
-		deparseExpr(lfirst(arg), context);
+		deparseExpr(linitial(node->args), context);
 		appendStringInfoChar(buf, ' ');
 	}
 
@@ -2735,12 +2732,8 @@ deparseOpExpr(OpExpr *node, deparse_expr_cxt *context)
 	deparseOperatorName(buf, form);
 
 	/* Deparse right operand. */
-	if (oprkind == 'l' || oprkind == 'b')
-	{
-		arg = list_tail(node->args);
-		appendStringInfoChar(buf, ' ');
-		deparseExpr(lfirst(arg), context);
-	}
+	appendStringInfoChar(buf, ' ');
+	deparseExpr(llast(node->args), context);
 
 	appendStringInfoChar(buf, ')');