Removal of operator_precedence_warning

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От Tom Lane
Тема Removal of operator_precedence_warning
Дата
Msg-id 2234320.1607117945@sss.pgh.pa.us
обсуждение исходный текст
Ответы Re: Removal of operator_precedence_warning  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Список pgsql-hackers
I think it's time for $SUBJECT.  We added this GUC in 9.5, which
will be EOL by the time of our next major release, and it was never
meant as more than a transitional aid.  Moreover, it's been buggy
as heck (cf abb164655, 05104f693, 01e0cbc4f, 4cae471d1), and the
fact that some of those errors went undetected for years shows that
it's not really gotten much field usage.

Hence, I propose the attached.  Comments?

            regards, tom lane

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 8cd3d6901c..4b60382778 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -9389,29 +9389,6 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
       </listitem>
      </varlistentry>

-     <varlistentry id="guc-operator-precedence-warning" xreflabel="operator_precedence_warning">
-      <term><varname>operator_precedence_warning</varname> (<type>boolean</type>)
-      <indexterm>
-       <primary><varname>operator_precedence_warning</varname> configuration parameter</primary>
-      </indexterm>
-      </term>
-      <listitem>
-       <para>
-        When on, the parser will emit a warning for any construct that might
-        have changed meanings since <productname>PostgreSQL</productname> 9.4 as a result
-        of changes in operator precedence.  This is useful for auditing
-        applications to see if precedence changes have broken anything; but it
-        is not meant to be kept turned on in production, since it will warn
-        about some perfectly valid, standard-compliant SQL code.
-        The default is <literal>off</literal>.
-       </para>
-
-       <para>
-        See <xref linkend="sql-precedence"/> for more information.
-       </para>
-      </listitem>
-     </varlistentry>
-
     <varlistentry id="guc-quote-all-identifiers" xreflabel="quote-all-identifiers">
       <term><varname>quote_all_identifiers</varname> (<type>boolean</type>)
       <indexterm>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 3fdd87823e..d66560b587 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1121,11 +1121,7 @@ SELECT 3 OPERATOR(pg_catalog.+) 4;
      cases, these changes will result in no behavioral change, or perhaps
      in <quote>no such operator</quote> failures which can be resolved by adding
      parentheses.  However there are corner cases in which a query might
-     change behavior without any parsing error being reported.  If you are
-     concerned about whether these changes have silently broken something,
-     you can test your application with the configuration
-     parameter <xref linkend="guc-operator-precedence-warning"/> turned on
-     to see if any warnings are logged.
+     change behavior without any parsing error being reported.
     </para>
    </note>
   </sect2>
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 9c73c605a4..8f5e4e71b2 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3264,9 +3264,6 @@ _outAExpr(StringInfo str, const A_Expr *node)
             appendStringInfoString(str, " NOT_BETWEEN_SYM ");
             WRITE_NODE_FIELD(name);
             break;
-        case AEXPR_PAREN:
-            appendStringInfoString(str, " PAREN");
-            break;
         default:
             appendStringInfoString(str, " ??");
             break;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index ecff4cd2ac..8f341ac006 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -59,7 +59,6 @@
 #include "nodes/nodeFuncs.h"
 #include "parser/gramparse.h"
 #include "parser/parser.h"
-#include "parser/parse_expr.h"
 #include "storage/lmgr.h"
 #include "utils/date.h"
 #include "utils/datetime.h"
@@ -13461,28 +13460,6 @@ c_expr:        columnref                                { $$ = $1; }
                         n->indirection = check_indirection($4, yyscanner);
                         $$ = (Node *)n;
                     }
-                    else if (operator_precedence_warning)
-                    {
-                        /*
-                         * If precedence warnings are enabled, insert
-                         * AEXPR_PAREN nodes wrapping all explicitly
-                         * parenthesized subexpressions; this prevents bogus
-                         * warnings from being issued when the ordering has
-                         * been forced by parentheses.  Take care that an
-                         * AEXPR_PAREN node has the same exprLocation as its
-                         * child, so as not to cause surprising changes in
-                         * error cursor positioning.
-                         *
-                         * In principle we should not be relying on a GUC to
-                         * decide whether to insert AEXPR_PAREN nodes.
-                         * However, since they have no effect except to
-                         * suppress warnings, it's probably safe enough; and
-                         * we'd just as soon not waste cycles on dummy parse
-                         * nodes if we don't have to.
-                         */
-                        $$ = (Node *) makeA_Expr(AEXPR_PAREN, NIL, $2, NULL,
-                                                 exprLocation($2));
-                    }
                     else
                         $$ = $2;
                 }
@@ -16516,16 +16493,10 @@ doNegateFloat(Value *v)
 static Node *
 makeAndExpr(Node *lexpr, Node *rexpr, int location)
 {
-    Node       *lexp = lexpr;
-
-    /* Look through AEXPR_PAREN nodes so they don't affect flattening */
-    while (IsA(lexp, A_Expr) &&
-           ((A_Expr *) lexp)->kind == AEXPR_PAREN)
-        lexp = ((A_Expr *) lexp)->lexpr;
     /* Flatten "a AND b AND c ..." to a single BoolExpr on sight */
-    if (IsA(lexp, BoolExpr))
+    if (IsA(lexpr, BoolExpr))
     {
-        BoolExpr *blexpr = (BoolExpr *) lexp;
+        BoolExpr *blexpr = (BoolExpr *) lexpr;

         if (blexpr->boolop == AND_EXPR)
         {
@@ -16539,16 +16510,10 @@ makeAndExpr(Node *lexpr, Node *rexpr, int location)
 static Node *
 makeOrExpr(Node *lexpr, Node *rexpr, int location)
 {
-    Node       *lexp = lexpr;
-
-    /* Look through AEXPR_PAREN nodes so they don't affect flattening */
-    while (IsA(lexp, A_Expr) &&
-           ((A_Expr *) lexp)->kind == AEXPR_PAREN)
-        lexp = ((A_Expr *) lexp)->lexpr;
     /* Flatten "a OR b OR c ..." to a single BoolExpr on sight */
-    if (IsA(lexp, BoolExpr))
+    if (IsA(lexpr, BoolExpr))
     {
-        BoolExpr *blexpr = (BoolExpr *) lexp;
+        BoolExpr *blexpr = (BoolExpr *) lexpr;

         if (blexpr->boolop == OR_EXPR)
         {
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 36002f059d..1e62d31aca 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:
@@ -2702,15 +2550,6 @@ transformTypeCast(ParseState *pstate, TypeCast *tc)
     /* Look up the type name first */
     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
@@ -3117,287 +2956,6 @@ make_nulltest_from_distinct(ParseState *pstate, A_Expr *distincta, Node *arg)
     return (Node *) nt;
 }

-/*
- * 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.
  *
diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index 9de0cff833..ce68663cc2 100644
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -1755,11 +1755,6 @@ FigureColnameInternal(Node *node, char **name)
                 *name = "nullif";
                 return 2;
             }
-            if (((A_Expr *) node)->kind == AEXPR_PAREN)
-            {
-                /* look through dummy parenthesis node */
-                return FigureColnameInternal(((A_Expr *) node)->lexpr, name);
-            }
             break;
         case T_TypeCast:
             strength = FigureColnameInternal(((TypeCast *) node)->arg,
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 635d91d50a..dabcbb0736 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1878,16 +1878,6 @@ static struct config_bool ConfigureNamesBool[] =
         NULL, NULL, NULL
     },

-    {
-        {"operator_precedence_warning", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
-            gettext_noop("Emit a warning for constructs that changed meaning since PostgreSQL 9.4."),
-            NULL,
-        },
-        &operator_precedence_warning,
-        false,
-        NULL, NULL, NULL
-    },
-
     {
         {"quote_all_identifiers", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
             gettext_noop("When generating SQL fragments, quote all identifiers."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 9c9091e601..b7fb2ec1fe 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -740,7 +740,6 @@
 #backslash_quote = safe_encoding    # on, off, or safe_encoding
 #escape_string_warning = on
 #lo_compat_privileges = off
-#operator_precedence_warning = off
 #quote_all_identifiers = off
 #standard_conforming_strings = on
 #synchronize_seqscans = on
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ec14fc2036..48a79a7657 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -265,8 +265,7 @@ typedef enum A_Expr_Kind
     AEXPR_BETWEEN,                /* name must be "BETWEEN" */
     AEXPR_NOT_BETWEEN,            /* name must be "NOT BETWEEN" */
     AEXPR_BETWEEN_SYM,            /* name must be "BETWEEN SYMMETRIC" */
-    AEXPR_NOT_BETWEEN_SYM,        /* name must be "NOT BETWEEN SYMMETRIC" */
-    AEXPR_PAREN                    /* nameless dummy node for parentheses */
+    AEXPR_NOT_BETWEEN_SYM        /* name must be "NOT BETWEEN SYMMETRIC" */
 } A_Expr_Kind;

 typedef struct A_Expr
diff --git a/src/include/parser/parse_expr.h b/src/include/parser/parse_expr.h
index b01d3b7dec..5668f88302 100644
--- a/src/include/parser/parse_expr.h
+++ b/src/include/parser/parse_expr.h
@@ -16,7 +16,6 @@
 #include "parser/parse_node.h"

 /* GUC parameters */
-extern bool operator_precedence_warning;
 extern bool Transform_null_equals;

 extern Node *transformExpr(ParseState *pstate, Node *expr, ParseExprKind exprKind);

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