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Remove support for postfix (right-unary) operators.

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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
This commit is contained in:
Tom Lane
2020-09-17 19:38:05 -04:00
parent 76f412ab31
commit 1ed6b89563
32 changed files with 279 additions and 339 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
src/backend/parser/gram.y
View File

@ -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
{

38
src/backend/parser/parse_expr.c
View File

@ -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",

128
src/backend/parser/parse_oper.c
View File

@ -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)
if (ltree == NULL)
{
/* right operator */
args = list_make1(ltree);
actual_arg_types[0] = ltypeId;
declared_arg_types[0] = opform->oprleft;
nargs = 1;
}
else if (ltree == NULL)
{
/* left operator */
/* prefix operator */
args = list_make1(rtree);
actual_arg_types[0] = rtypeId;
declared_arg_types[0] = opform->oprright;