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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
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38
src/backend/parser/parse_expr.c
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@ -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",