Remove operator_precedence_warning.

This GUC was always intended as a temporary solution to help with
finding 9.4-to-9.5 migration issues.  Now that all pre-9.5 branches
are out of support, and 9.5 will be too before v14 is released,
it seems like it's okay to drop it.  Doing so allows removal of
several hundred lines of poorly-tested code in parse_expr.c,
which have been a fertile source of bugs when people did use this.

Discussion: https://postgr.es/m/2234320.1607117945@sss.pgh.pa.us

1 files changed, 4 insertions, 446 deletions

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 36002f059d1..1e62d31aca7 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -39,53 +39,8 @@
 #include "utils/xml.h"
 
 /* GUC parameters */
-bool		operator_precedence_warning = false;
 bool		Transform_null_equals = false;
 
-/*
- * Node-type groups for operator precedence warnings
- * We use zero for everything not otherwise classified
- */
-#define PREC_GROUP_POSTFIX_IS	1	/* postfix IS tests (NullTest, etc) */
-#define PREC_GROUP_INFIX_IS		2	/* infix IS (IS DISTINCT FROM, etc) */
-#define PREC_GROUP_LESS			3	/* < > */
-#define PREC_GROUP_EQUAL		4	/* = */
-#define PREC_GROUP_LESS_EQUAL	5	/* <= >= <> */
-#define PREC_GROUP_LIKE			6	/* LIKE ILIKE SIMILAR */
-#define PREC_GROUP_BETWEEN		7	/* BETWEEN */
-#define PREC_GROUP_IN			8	/* IN */
-#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_ANY_ALL		12	/* ANY/ALL */
-#define PREC_GROUP_INFIX_OP		13	/* generic infix operators */
-#define PREC_GROUP_PREFIX_OP	14	/* generic prefix operators */
-
-/*
- * Map precedence groupings to old precedence ordering
- *
- * Old precedence order:
- * 1. NOT
- * 2. =
- * 3. < >
- * 4. LIKE ILIKE SIMILAR
- * 5. BETWEEN
- * 6. IN
- * 7. ANY ALL
- * 8. generic Op, including <= => <>
- * 9. generic prefix Op
- * 10. IS tests (NullTest, BooleanTest, etc)
- *
- * NOT BETWEEN etc map to BETWEEN etc when considered as being on the left,
- * but to NOT when considered as being on the right, because of the buggy
- * precedence handling of those productions in the old grammar.
- */
-static const int oldprecedence_l[] = {
-	0, 10, 10, 3, 2, 8, 4, 5, 6, 4, 5, 6, 7, 8, 9
-};
-static const int oldprecedence_r[] = {
-	0, 10, 10, 3, 2, 8, 4, 5, 6, 1, 1, 1, 7, 8, 9
-};
 
 static Node *transformExprRecurse(ParseState *pstate, Node *expr);
 static Node *transformParamRef(ParseState *pstate, ParamRef *pref);
@@ -127,11 +82,6 @@ static Expr *make_distinct_op(ParseState *pstate, List *opname,
 							  Node *ltree, Node *rtree, int location);
 static Node *make_nulltest_from_distinct(ParseState *pstate,
 										 A_Expr *distincta, Node *arg);
-static int	operator_precedence_group(Node *node, const char **nodename);
-static void emit_precedence_warnings(ParseState *pstate,
-									 int opgroup, const char *opname,
-									 Node *lchild, Node *rchild,
-									 int location);
 
 
 /*
@@ -242,9 +192,6 @@ transformExprRecurse(ParseState *pstate, Node *expr)
 					case AEXPR_NOT_BETWEEN_SYM:
 						result = transformAExprBetween(pstate, a);
 						break;
-					case AEXPR_PAREN:
-						result = transformExprRecurse(pstate, a->lexpr);
-						break;
 					default:
 						elog(ERROR, "unrecognized A_Expr kind: %d", a->kind);
 						result = NULL;	/* keep compiler quiet */
@@ -315,11 +262,6 @@ transformExprRecurse(ParseState *pstate, Node *expr)
 			{
 				NullTest   *n = (NullTest *) expr;
 
-				if (operator_precedence_warning)
-					emit_precedence_warnings(pstate, PREC_GROUP_POSTFIX_IS, "IS",
-											 (Node *) n->arg, NULL,
-											 n->location);
-
 				n->arg = (Expr *) transformExprRecurse(pstate, (Node *) n->arg);
 				/* the argument can be any type, so don't coerce it */
 				n->argisrow = type_is_rowtype(exprType((Node *) n->arg));
@@ -926,26 +868,6 @@ transformAExprOp(ParseState *pstate, A_Expr *a)
 	Node	   *rexpr = a->rexpr;
 	Node	   *result;
 
-	if (operator_precedence_warning)
-	{
-		int			opgroup;
-		const char *opname;
-
-		opgroup = operator_precedence_group((Node *) a, &opname);
-		if (opgroup > 0)
-			emit_precedence_warnings(pstate, opgroup, opname,
-									 lexpr, rexpr,
-									 a->location);
-
-		/* Look through AEXPR_PAREN nodes so they don't affect tests below */
-		while (lexpr && IsA(lexpr, A_Expr) &&
-			   ((A_Expr *) lexpr)->kind == AEXPR_PAREN)
-			lexpr = ((A_Expr *) lexpr)->lexpr;
-		while (rexpr && IsA(rexpr, A_Expr) &&
-			   ((A_Expr *) rexpr)->kind == AEXPR_PAREN)
-			rexpr = ((A_Expr *) rexpr)->lexpr;
-	}
-
 	/*
 	 * Special-case "foo = NULL" and "NULL = foo" for compatibility with
 	 * standards-broken products (like Microsoft's).  Turn these into IS NULL
@@ -1023,17 +945,8 @@ transformAExprOp(ParseState *pstate, A_Expr *a)
 static Node *
 transformAExprOpAny(ParseState *pstate, A_Expr *a)
 {
-	Node	   *lexpr = a->lexpr;
-	Node	   *rexpr = a->rexpr;
-
-	if (operator_precedence_warning)
-		emit_precedence_warnings(pstate, PREC_GROUP_ANY_ALL,
-								 strVal(llast(a->name)),
-								 lexpr, NULL,
-								 a->location);
-
-	lexpr = transformExprRecurse(pstate, lexpr);
-	rexpr = transformExprRecurse(pstate, rexpr);
+	Node	   *lexpr = transformExprRecurse(pstate, a->lexpr);
+	Node	   *rexpr = transformExprRecurse(pstate, a->rexpr);
 
 	return (Node *) make_scalar_array_op(pstate,
 										 a->name,
@@ -1046,17 +959,8 @@ transformAExprOpAny(ParseState *pstate, A_Expr *a)
 static Node *
 transformAExprOpAll(ParseState *pstate, A_Expr *a)
 {
-	Node	   *lexpr = a->lexpr;
-	Node	   *rexpr = a->rexpr;
-
-	if (operator_precedence_warning)
-		emit_precedence_warnings(pstate, PREC_GROUP_ANY_ALL,
-								 strVal(llast(a->name)),
-								 lexpr, NULL,
-								 a->location);
-
-	lexpr = transformExprRecurse(pstate, lexpr);
-	rexpr = transformExprRecurse(pstate, rexpr);
+	Node	   *lexpr = transformExprRecurse(pstate, a->lexpr);
+	Node	   *rexpr = transformExprRecurse(pstate, a->rexpr);
 
 	return (Node *) make_scalar_array_op(pstate,
 										 a->name,
@@ -1073,11 +977,6 @@ transformAExprDistinct(ParseState *pstate, A_Expr *a)
 	Node	   *rexpr = a->rexpr;
 	Node	   *result;
 
-	if (operator_precedence_warning)
-		emit_precedence_warnings(pstate, PREC_GROUP_INFIX_IS, "IS",
-								 lexpr, rexpr,
-								 a->location);
-
 	/*
 	 * If either input is an undecorated NULL literal, transform to a NullTest
 	 * on the other input. That's simpler to process than a full DistinctExpr,
@@ -1183,13 +1082,6 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
 	else
 		useOr = true;
 
-	if (operator_precedence_warning)
-		emit_precedence_warnings(pstate,
-								 useOr ? PREC_GROUP_IN : PREC_GROUP_NOT_IN,
-								 "IN",
-								 a->lexpr, NULL,
-								 a->location);
-
 	/*
 	 * We try to generate a ScalarArrayOpExpr from IN/NOT IN, but this is only
 	 * possible if there is a suitable array type available.  If not, we fall
@@ -1342,22 +1234,6 @@ transformAExprBetween(ParseState *pstate, A_Expr *a)
 	bexpr = (Node *) linitial(args);
 	cexpr = (Node *) lsecond(args);
 
-	if (operator_precedence_warning)
-	{
-		int			opgroup;
-		const char *opname;
-
-		opgroup = operator_precedence_group((Node *) a, &opname);
-		emit_precedence_warnings(pstate, opgroup, opname,
-								 aexpr, cexpr,
-								 a->location);
-		/* We can ignore bexpr thanks to syntactic restrictions */
-		/* Wrap subexpressions to prevent extra warnings */
-		aexpr = (Node *) makeA_Expr(AEXPR_PAREN, NIL, aexpr, NULL, -1);
-		bexpr = (Node *) makeA_Expr(AEXPR_PAREN, NIL, bexpr, NULL, -1);
-		cexpr = (Node *) makeA_Expr(AEXPR_PAREN, NIL, cexpr, NULL, -1);
-	}
-
 	/*
 	 * Build the equivalent comparison expression.  Make copies of
 	 * multiply-referenced subexpressions for safety.  (XXX this is really
@@ -1964,19 +1840,6 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
 		List	   *right_list;
 		ListCell   *l;
 
-		if (operator_precedence_warning)
-		{
-			if (sublink->operName == NIL)
-				emit_precedence_warnings(pstate, PREC_GROUP_IN, "IN",
-										 sublink->testexpr, NULL,
-										 sublink->location);
-			else
-				emit_precedence_warnings(pstate, PREC_GROUP_ANY_ALL,
-										 strVal(llast(sublink->operName)),
-										 sublink->testexpr, NULL,
-										 sublink->location);
-		}
-
 		/*
 		 * If the source was "x IN (select)", convert to "x = ANY (select)".
 		 */
@@ -2076,11 +1939,6 @@ transformArrayExpr(ParseState *pstate, A_ArrayExpr *a,
 		Node	   *e = (Node *) lfirst(element);
 		Node	   *newe;
 
-		/* Look through AEXPR_PAREN nodes so they don't affect test below */
-		while (e && IsA(e, A_Expr) &&
-			   ((A_Expr *) e)->kind == AEXPR_PAREN)
-			e = ((A_Expr *) e)->lexpr;
-
 		/*
 		 * If an element is itself an A_ArrayExpr, recurse directly so that we
 		 * can pass down any target type we were given.
@@ -2389,11 +2247,6 @@ transformXmlExpr(ParseState *pstate, XmlExpr *x)
 	ListCell   *lc;
 	int			i;
 
-	if (operator_precedence_warning && x->op == IS_DOCUMENT)
-		emit_precedence_warnings(pstate, PREC_GROUP_POSTFIX_IS, "IS",
-								 (Node *) linitial(x->args), NULL,
-								 x->location);
-
 	newx = makeNode(XmlExpr);
 	newx->op = x->op;
 	if (x->name)
@@ -2564,11 +2417,6 @@ transformBooleanTest(ParseState *pstate, BooleanTest *b)
 {
 	const char *clausename;
 
-	if (operator_precedence_warning)
-		emit_precedence_warnings(pstate, PREC_GROUP_POSTFIX_IS, "IS",
-								 (Node *) b->arg, NULL,
-								 b->location);
-
 	switch (b->booltesttype)
 	{
 		case IS_TRUE:
@@ -2703,15 +2551,6 @@ transformTypeCast(ParseState *pstate, TypeCast *tc)
 	typenameTypeIdAndMod(pstate, tc->typeName, &targetType, &targetTypmod);
 
 	/*
-	 * Look through any AEXPR_PAREN nodes that may have been inserted thanks
-	 * to operator_precedence_warning.  Otherwise, ARRAY[]::foo[] behaves
-	 * differently from (ARRAY[])::foo[].
-	 */
-	while (arg && IsA(arg, A_Expr) &&
-		   ((A_Expr *) arg)->kind == AEXPR_PAREN)
-		arg = ((A_Expr *) arg)->lexpr;
-
-	/*
 	 * If the subject of the typecast is an ARRAY[] construct and the target
 	 * type is an array type, we invoke transformArrayExpr() directly so that
 	 * we can pass down the type information.  This avoids some cases where
@@ -3118,287 +2957,6 @@ make_nulltest_from_distinct(ParseState *pstate, A_Expr *distincta, Node *arg)
 }
 
 /*
- * Identify node's group for operator precedence warnings
- *
- * For items in nonzero groups, also return a suitable node name into *nodename
- *
- * Note: group zero is used for nodes that are higher or lower precedence
- * than everything that changed precedence; we need never issue warnings
- * related to such nodes.
- */
-static int
-operator_precedence_group(Node *node, const char **nodename)
-{
-	int			group = 0;
-
-	*nodename = NULL;
-	if (node == NULL)
-		return 0;
-
-	if (IsA(node, A_Expr))
-	{
-		A_Expr	   *aexpr = (A_Expr *) node;
-
-		if (aexpr->kind == AEXPR_OP &&
-			aexpr->lexpr != NULL &&
-			aexpr->rexpr != NULL)
-		{
-			/* binary operator */
-			if (list_length(aexpr->name) == 1)
-			{
-				*nodename = strVal(linitial(aexpr->name));
-				/* Ignore if op was always higher priority than IS-tests */
-				if (strcmp(*nodename, "+") == 0 ||
-					strcmp(*nodename, "-") == 0 ||
-					strcmp(*nodename, "*") == 0 ||
-					strcmp(*nodename, "/") == 0 ||
-					strcmp(*nodename, "%") == 0 ||
-					strcmp(*nodename, "^") == 0)
-					group = 0;
-				else if (strcmp(*nodename, "<") == 0 ||
-						 strcmp(*nodename, ">") == 0)
-					group = PREC_GROUP_LESS;
-				else if (strcmp(*nodename, "=") == 0)
-					group = PREC_GROUP_EQUAL;
-				else if (strcmp(*nodename, "<=") == 0 ||
-						 strcmp(*nodename, ">=") == 0 ||
-						 strcmp(*nodename, "<>") == 0)
-					group = PREC_GROUP_LESS_EQUAL;
-				else
-					group = PREC_GROUP_INFIX_OP;
-			}
-			else
-			{
-				/* schema-qualified operator syntax */
-				*nodename = "OPERATOR()";
-				group = PREC_GROUP_INFIX_OP;
-			}
-		}
-		else if (aexpr->kind == AEXPR_OP &&
-				 aexpr->lexpr == NULL &&
-				 aexpr->rexpr != NULL)
-		{
-			/* prefix operator */
-			if (list_length(aexpr->name) == 1)
-			{
-				*nodename = strVal(linitial(aexpr->name));
-				/* Ignore if op was always higher priority than IS-tests */
-				if (strcmp(*nodename, "+") == 0 ||
-					strcmp(*nodename, "-") == 0)
-					group = 0;
-				else
-					group = PREC_GROUP_PREFIX_OP;
-			}
-			else
-			{
-				/* schema-qualified operator syntax */
-				*nodename = "OPERATOR()";
-				group = PREC_GROUP_PREFIX_OP;
-			}
-		}
-		else if (aexpr->kind == AEXPR_OP_ANY ||
-				 aexpr->kind == AEXPR_OP_ALL)
-		{
-			*nodename = strVal(llast(aexpr->name));
-			group = PREC_GROUP_ANY_ALL;
-		}
-		else if (aexpr->kind == AEXPR_DISTINCT ||
-				 aexpr->kind == AEXPR_NOT_DISTINCT)
-		{
-			*nodename = "IS";
-			group = PREC_GROUP_INFIX_IS;
-		}
-		else if (aexpr->kind == AEXPR_IN)
-		{
-			*nodename = "IN";
-			if (strcmp(strVal(linitial(aexpr->name)), "=") == 0)
-				group = PREC_GROUP_IN;
-			else
-				group = PREC_GROUP_NOT_IN;
-		}
-		else if (aexpr->kind == AEXPR_LIKE)
-		{
-			*nodename = "LIKE";
-			if (strcmp(strVal(linitial(aexpr->name)), "~~") == 0)
-				group = PREC_GROUP_LIKE;
-			else
-				group = PREC_GROUP_NOT_LIKE;
-		}
-		else if (aexpr->kind == AEXPR_ILIKE)
-		{
-			*nodename = "ILIKE";
-			if (strcmp(strVal(linitial(aexpr->name)), "~~*") == 0)
-				group = PREC_GROUP_LIKE;
-			else
-				group = PREC_GROUP_NOT_LIKE;
-		}
-		else if (aexpr->kind == AEXPR_SIMILAR)
-		{
-			*nodename = "SIMILAR";
-			if (strcmp(strVal(linitial(aexpr->name)), "~") == 0)
-				group = PREC_GROUP_LIKE;
-			else
-				group = PREC_GROUP_NOT_LIKE;
-		}
-		else if (aexpr->kind == AEXPR_BETWEEN ||
-				 aexpr->kind == AEXPR_BETWEEN_SYM)
-		{
-			Assert(list_length(aexpr->name) == 1);
-			*nodename = strVal(linitial(aexpr->name));
-			group = PREC_GROUP_BETWEEN;
-		}
-		else if (aexpr->kind == AEXPR_NOT_BETWEEN ||
-				 aexpr->kind == AEXPR_NOT_BETWEEN_SYM)
-		{
-			Assert(list_length(aexpr->name) == 1);
-			*nodename = strVal(linitial(aexpr->name));
-			group = PREC_GROUP_NOT_BETWEEN;
-		}
-	}
-	else if (IsA(node, NullTest) ||
-			 IsA(node, BooleanTest))
-	{
-		*nodename = "IS";
-		group = PREC_GROUP_POSTFIX_IS;
-	}
-	else if (IsA(node, XmlExpr))
-	{
-		XmlExpr    *x = (XmlExpr *) node;
-
-		if (x->op == IS_DOCUMENT)
-		{
-			*nodename = "IS";
-			group = PREC_GROUP_POSTFIX_IS;
-		}
-	}
-	else if (IsA(node, SubLink))
-	{
-		SubLink    *s = (SubLink *) node;
-
-		if (s->subLinkType == ANY_SUBLINK ||
-			s->subLinkType == ALL_SUBLINK)
-		{
-			if (s->operName == NIL)
-			{
-				*nodename = "IN";
-				group = PREC_GROUP_IN;
-			}
-			else
-			{
-				*nodename = strVal(llast(s->operName));
-				group = PREC_GROUP_ANY_ALL;
-			}
-		}
-	}
-	else if (IsA(node, BoolExpr))
-	{
-		/*
-		 * Must dig into NOTs to see if it's IS NOT DOCUMENT or NOT IN.  This
-		 * opens us to possibly misrecognizing, eg, NOT (x IS DOCUMENT) as a
-		 * problematic construct.  We can tell the difference by checking
-		 * whether the parse locations of the two nodes are identical.
-		 *
-		 * Note that when we are comparing the child node to its own children,
-		 * we will not know that it was a NOT.  Fortunately, that doesn't
-		 * matter for these cases.
-		 */
-		BoolExpr   *b = (BoolExpr *) node;
-
-		if (b->boolop == NOT_EXPR)
-		{
-			Node	   *child = (Node *) linitial(b->args);
-
-			if (IsA(child, XmlExpr))
-			{
-				XmlExpr    *x = (XmlExpr *) child;
-
-				if (x->op == IS_DOCUMENT &&
-					x->location == b->location)
-				{
-					*nodename = "IS";
-					group = PREC_GROUP_POSTFIX_IS;
-				}
-			}
-			else if (IsA(child, SubLink))
-			{
-				SubLink    *s = (SubLink *) child;
-
-				if (s->subLinkType == ANY_SUBLINK && s->operName == NIL &&
-					s->location == b->location)
-				{
-					*nodename = "IN";
-					group = PREC_GROUP_NOT_IN;
-				}
-			}
-		}
-	}
-	return group;
-}
-
-/*
- * helper routine for delivering 9.4-to-9.5 operator precedence warnings
- *
- * opgroup/opname/location represent some parent node
- * lchild, rchild are its left and right children (either could be NULL)
- *
- * This should be called before transforming the child nodes, since if a
- * precedence-driven parsing change has occurred in a query that used to work,
- * it's quite possible that we'll get a semantic failure while analyzing the
- * child expression.  We want to produce the warning before that happens.
- * In any case, operator_precedence_group() expects untransformed input.
- */
-static void
-emit_precedence_warnings(ParseState *pstate,
-						 int opgroup, const char *opname,
-						 Node *lchild, Node *rchild,
-						 int location)
-{
-	int			cgroup;
-	const char *copname;
-
-	Assert(opgroup > 0);
-
-	/*
-	 * 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 the
-	 * grouping is syntactically forced regardless of precedence.
-	 */
-	cgroup = operator_precedence_group(lchild, &copname);
-	if (cgroup > 0)
-	{
-		if (oldprecedence_l[cgroup] < oldprecedence_r[opgroup] &&
-			cgroup != PREC_GROUP_IN &&
-			cgroup != PREC_GROUP_NOT_IN &&
-			cgroup != PREC_GROUP_ANY_ALL &&
-			cgroup != PREC_GROUP_POSTFIX_IS)
-			ereport(WARNING,
-					(errmsg("operator precedence change: %s is now lower precedence than %s",
-							opname, copname),
-					 parser_errposition(pstate, location)));
-	}
-
-	/*
-	 * Complain if right child, which should be higher precedence according to
-	 * current rules, used to be same or lower precedence.
-	 *
-	 * Exception to precedence rules: if right child is a prefix operator, the
-	 * grouping is syntactically forced regardless of precedence.
-	 */
-	cgroup = operator_precedence_group(rchild, &copname);
-	if (cgroup > 0)
-	{
-		if (oldprecedence_r[cgroup] <= oldprecedence_l[opgroup] &&
-			cgroup != PREC_GROUP_PREFIX_OP)
-			ereport(WARNING,
-					(errmsg("operator precedence change: %s is now lower precedence than %s",
-							opname, copname),
-					 parser_errposition(pstate, location)));
-	}
-}
-
-/*
  * Produce a string identifying an expression by kind.
  *
  * Note: when practical, use a simple SQL keyword for the result.  If that