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Implement SQL-compliant treatment of row comparisons for < <= > >= cases

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(previously we only did = and <> correctly).  Also, allow row comparisons
with any operators that are in btree opclasses, not only those with these
specific names.  This gets rid of a whole lot of indefensible assumptions
about the behavior of particular operators based on their names ... though
it's still true that IN and NOT IN expand to "= ANY".  The patch adds a
RowCompareExpr expression node type, and makes some changes in the
representation of ANY/ALL/ROWCOMPARE SubLinks so that they can share code
with RowCompareExpr.

I have not yet done anything about making RowCompareExpr an indexable
operator, but will look at that soon.

initdb forced due to changes in stored rules.
This commit is contained in:
Tom Lane
2005-12-28 01:30:02 +00:00
parent a37422e042
commit 6e07709760
26 changed files with 1452 additions and 659 deletions
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450
src/backend/parser/parse_expr.c
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@ -8,21 +8,20 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.188 2005/11/28 04:35:31 tgl Exp $
* $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.189 2005/12/28 01:30:00 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "commands/dbcommands.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/params.h"
#include "nodes/plannodes.h"
#include "optimizer/clauses.h"
#include "parser/analyze.h"
#include "parser/gramparse.h"
#include "parser/parse_coerce.h"
@ -33,7 +32,7 @@
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
bool Transform_null_equals = false;
@ -64,8 +63,8 @@ static Node *transformIndirection(ParseState *pstate, Node *basenode,
List *indirection);
static Node *typecast_expression(ParseState *pstate, Node *expr,
TypeName *typename);
static Node *make_row_op(ParseState *pstate, List *opname,
RowExpr *lrow, RowExpr *rrow);
static Node *make_row_comparison_op(ParseState *pstate, List *opname,
List *largs, List *rargs);
static Node *make_row_distinct_op(ParseState *pstate, List *opname,
RowExpr *lrow, RowExpr *rrow);
static Expr *make_distinct_op(ParseState *pstate, List *opname,
@ -592,14 +591,14 @@ transformAExprOp(ParseState *pstate, A_Expr *a)
((SubLink *) rexpr)->subLinkType == EXPR_SUBLINK)
{
/*
* Convert "row op subselect" into a MULTIEXPR sublink. Formerly the
* Convert "row op subselect" into a ROWCOMPARE sublink. Formerly the
* grammar did this, but now that a row construct is allowed anywhere
* in expressions, it's easier to do it here.
*/
SubLink *s = (SubLink *) rexpr;
s->subLinkType = MULTIEXPR_SUBLINK;
s->lefthand = ((RowExpr *) lexpr)->args;
s->subLinkType = ROWCOMPARE_SUBLINK;
s->testexpr = lexpr;
s->operName = a->name;
result = transformExpr(pstate, (Node *) s);
}
@ -612,10 +611,10 @@ transformAExprOp(ParseState *pstate, A_Expr *a)
Assert(IsA(lexpr, RowExpr));
Assert(IsA(rexpr, RowExpr));
result = make_row_op(pstate,
a->name,
(RowExpr *) lexpr,
(RowExpr *) rexpr);
result = make_row_comparison_op(pstate,
a->name,
((RowExpr *) lexpr)->args,
((RowExpr *) rexpr)->args);
}
else
{
@ -885,10 +884,10 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("arguments of row IN must all be row expressions")));
cmp = make_row_op(pstate,
a->name,
(RowExpr *) copyObject(lexpr),
(RowExpr *) rexpr);
cmp = make_row_comparison_op(pstate,
a->name,
(List *) copyObject(((RowExpr *) lexpr)->args),
((RowExpr *) rexpr)->args);
}
else
cmp = (Node *) make_op(pstate,
@ -1080,13 +1079,11 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
if (sublink->subLinkType == EXISTS_SUBLINK)
{
/*
* EXISTS needs no lefthand or combining operator. These fields
* should be NIL already, but make sure.
* EXISTS needs no test expression or combining operator.
* These fields should be null already, but make sure.
*/
sublink->lefthand = NIL;
sublink->testexpr = NULL;
sublink->operName = NIL;
sublink->operOids = NIL;
sublink->useOr = FALSE;
}
else if (sublink->subLinkType == EXPR_SUBLINK ||
sublink->subLinkType == ARRAY_SUBLINK)
@ -1111,128 +1108,72 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
}
/*
* EXPR and ARRAY need no lefthand or combining operator. These fields
* should be NIL already, but make sure.
* EXPR and ARRAY need no test expression or combining operator.
* These fields should be null already, but make sure.
*/
sublink->lefthand = NIL;
sublink->testexpr = NULL;
sublink->operName = NIL;
sublink->operOids = NIL;
sublink->useOr = FALSE;
}
else
{
/* ALL, ANY, or MULTIEXPR: generate operator list */
List *left_list = sublink->lefthand;
List *right_list = qtree->targetList;
int row_length = list_length(left_list);
bool needNot = false;
List *op = sublink->operName;
char *opname = strVal(llast(op));
/* ALL, ANY, or ROWCOMPARE: generate row-comparing expression */
Node *lefthand;
List *left_list;
List *right_list;
ListCell *l;
ListCell *ll_item;
/* transform lefthand expressions */
foreach(l, left_list)
lfirst(l) = transformExpr(pstate, lfirst(l));
/*
* If the expression is "<> ALL" (with unqualified opname) then
* convert it to "NOT IN". This is a hack to improve efficiency of
* expressions output by pre-7.4 Postgres.
* Transform lefthand expression, and convert to a list
*/
if (sublink->subLinkType == ALL_SUBLINK &&
list_length(op) == 1 && strcmp(opname, "<>") == 0)
{
sublink->subLinkType = ANY_SUBLINK;
opname = pstrdup("=");
op = list_make1(makeString(opname));
sublink->operName = op;
needNot = true;
}
/* Set useOr if op is "<>" (possibly qualified) */
if (strcmp(opname, "<>") == 0)
sublink->useOr = TRUE;
lefthand = transformExpr(pstate, sublink->testexpr);
if (lefthand && IsA(lefthand, RowExpr))
left_list = ((RowExpr *) lefthand)->args;
else
sublink->useOr = FALSE;
/* Combining operators other than =/<> is dubious... */
if (row_length != 1 &&
strcmp(opname, "=") != 0 &&
strcmp(opname, "<>") != 0)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("row comparison cannot use operator %s",
opname)));
left_list = list_make1(lefthand);
/*
* To build the list of combining operator OIDs, we must scan
* subquery's targetlist to find values that will be matched against
* lefthand values. We need to ignore resjunk targets, so doing the
* outer iteration over right_list is easier than doing it over
* left_list.
* Build a list of PARAM_SUBLINK nodes representing the
* output columns of the subquery.
*/
sublink->operOids = NIL;
ll_item = list_head(left_list);
foreach(l, right_list)
right_list = NIL;
foreach(l, qtree->targetList)
{
TargetEntry *tent = (TargetEntry *) lfirst(l);
Node *lexpr;
Operator optup;
Form_pg_operator opform;
Param *param;
if (tent->resjunk)
continue;
if (ll_item == NULL)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("subquery has too many columns")));
lexpr = lfirst(ll_item);
ll_item = lnext(ll_item);
param = makeNode(Param);
param->paramkind = PARAM_SUBLINK;
param->paramid = (AttrNumber) tent->resno;
param->paramtype = exprType((Node *) tent->expr);
/*
* It's OK to use oper() not compatible_oper() here, because
* make_subplan() will insert type coercion calls if needed.
*/
optup = oper(op,
exprType(lexpr),
exprType((Node *) tent->expr),
false);
opform = (Form_pg_operator) GETSTRUCT(optup);
if (opform->oprresult != BOOLOID)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("operator %s must return type boolean, not type %s",
opname,
format_type_be(opform->oprresult)),
errhint("The operator of a quantified predicate subquery must return type boolean.")));
if (get_func_retset(opform->oprcode))
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("operator %s must not return a set",
opname),
errhint("The operator of a quantified predicate subquery must return type boolean.")));
sublink->operOids = lappend_oid(sublink->operOids,
oprid(optup));
ReleaseSysCache(optup);
right_list = lappend(right_list, param);
}
if (ll_item != NULL)
/*
* We could rely on make_row_comparison_op to complain if the
* list lengths differ, but we prefer to generate a more specific
* error message.
*/
if (list_length(left_list) < list_length(right_list))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("subquery has too many columns")));
if (list_length(left_list) > list_length(right_list))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("subquery has too few columns")));
if (needNot)
{
result = coerce_to_boolean(pstate, result, "NOT");
result = (Node *) makeBoolExpr(NOT_EXPR,
list_make1(result));
}
/*
* Identify the combining operator(s) and generate a suitable
* row-comparison expression.
*/
sublink->testexpr = make_row_comparison_op(pstate,
sublink->operName,
left_list,
right_list);
}
return result;
@ -1673,6 +1614,9 @@ exprType(Node *expr)
case T_RowExpr:
type = ((RowExpr *) expr)->row_typeid;
break;
case T_RowCompareExpr:
type = BOOLOID;
break;
case T_CoalesceExpr:
type = ((CoalesceExpr *) expr)->coalescetype;
break;
@ -1953,76 +1897,258 @@ typecast_expression(ParseState *pstate, Node *expr, TypeName *typename)
}
/*
* Transform a "row op row" construct
* Transform a "row compare-op row" construct
*
* The input RowExprs are already transformed
* The inputs are lists of already-transformed expressions.
* As with coerce_type, pstate may be NULL if no special unknown-Param
* processing is wanted.
*
* The output may be a single OpExpr, an AND or OR combination of OpExprs,
* or a RowCompareExpr. In all cases it is guaranteed to return boolean.
* The AND, OR, and RowCompareExpr cases further imply things about the
* behavior of the operators (ie, they behave as =, <>, or < <= > >=).
*/
static Node *
make_row_op(ParseState *pstate, List *opname,
RowExpr *lrow, RowExpr *rrow)
make_row_comparison_op(ParseState *pstate, List *opname,
List *largs, List *rargs)
{
Node *result = NULL;
List *largs = lrow->args;
List *rargs = rrow->args;
RowCompareExpr *rcexpr;
RowCompareType rctype;
List *opexprs;
List *opnos;
List *opclasses;
ListCell *l,
*r;
char *oprname;
BoolExprType boolop;
List **opclass_lists;
List **opstrat_lists;
Bitmapset *strats;
int nopers;
int i;
if (list_length(largs) != list_length(rargs))
nopers = list_length(largs);
if (nopers != list_length(rargs))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("unequal number of entries in row expressions")));
/*
* XXX it's really wrong to generate a simple AND combination for < <= >
* >=. We probably need to invent a new runtime node type to handle those
* correctly. For the moment, though, keep on doing this ...
* We can't compare zero-length rows because there is no principled
* basis for figuring out what the operator is.
*/
oprname = strVal(llast(opname));
if ((strcmp(oprname, "=") == 0) ||
(strcmp(oprname, "<") == 0) ||
(strcmp(oprname, "<=") == 0) ||
(strcmp(oprname, ">") == 0) ||
(strcmp(oprname, ">=") == 0))
boolop = AND_EXPR;
else if (strcmp(oprname, "<>") == 0)
boolop = OR_EXPR;
else
{
if (nopers == 0)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("operator %s is not supported for row expressions",
oprname)));
boolop = 0; /* keep compiler quiet */
}
errmsg("cannot compare rows of zero length")));
/*
* Identify all the pairwise operators, using make_op so that
* behavior is the same as in the simple scalar case.
*/
opexprs = NIL;
forboth(l, largs, r, rargs)
{
Node *larg = (Node *) lfirst(l);
Node *rarg = (Node *) lfirst(r);
Node *cmp;
OpExpr *cmp;
cmp = (Node *) make_op(pstate, opname, larg, rarg);
cmp = coerce_to_boolean(pstate, cmp, "row comparison");
if (result == NULL)
result = cmp;
else
result = (Node *) makeBoolExpr(boolop,
list_make2(result, cmp));
cmp = (OpExpr *) make_op(pstate, opname, larg, rarg);
Assert(IsA(cmp, OpExpr));
/*
* We don't use coerce_to_boolean here because we insist on the
* operator yielding boolean directly, not via coercion. If it
* doesn't yield bool it won't be in any index opclasses...
*/
if (cmp->opresulttype != BOOLOID)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("row comparison operator must yield type boolean, "
"not type %s",
format_type_be(cmp->opresulttype))));
if (expression_returns_set((Node *) cmp))
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("row comparison operator must not return a set")));
opexprs = lappend(opexprs, cmp);
}
if (result == NULL)
/*
* If rows are length 1, just return the single operator. In this
* case we don't insist on identifying btree semantics for the operator
* (but we still require it to return boolean).
*/
if (nopers == 1)
return (Node *) linitial(opexprs);
/*
* Now we must determine which row comparison semantics (= <> < <= > >=)
* apply to this set of operators. We look for btree opclasses containing
* the operators, and see which interpretations (strategy numbers) exist
* for each operator.
*/
opclass_lists = (List **) palloc(nopers * sizeof(List *));
opstrat_lists = (List **) palloc(nopers * sizeof(List *));
strats = NULL;
i = 0;
foreach(l, opexprs)
{
/* zero-length rows? Generate constant TRUE or FALSE */
if (boolop == AND_EXPR)
result = makeBoolConst(true, false);
Bitmapset *this_strats;
ListCell *j;
get_op_btree_interpretation(((OpExpr *) lfirst(l))->opno,
&opclass_lists[i], &opstrat_lists[i]);
/*
* convert strategy number list to a Bitmapset to make the intersection
* calculation easy.
*/
this_strats = NULL;
foreach(j, opstrat_lists[i])
{
this_strats = bms_add_member(this_strats, lfirst_int(j));
}
if (i == 0)
strats = this_strats;
else
result = makeBoolConst(false, false);
strats = bms_int_members(strats, this_strats);
i++;
}
return result;
switch (bms_membership(strats))
{
case BMS_EMPTY_SET:
/* No common interpretation, so fail */
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("could not determine interpretation of row comparison operator %s",
strVal(llast(opname))),
errhint("Row comparison operators must be associated with btree operator classes.")));
rctype = 0; /* keep compiler quiet */
break;
case BMS_SINGLETON:
/* Simple case: just one possible interpretation */
rctype = bms_singleton_member(strats);
break;
case BMS_MULTIPLE:
default: /* keep compiler quiet */
{
/*
* Prefer the interpretation with the most default opclasses.
*/
int best_defaults = 0;
bool multiple_best = false;
int this_rctype;
rctype = 0; /* keep compiler quiet */
while ((this_rctype = bms_first_member(strats)) >= 0)
{
int ndefaults = 0;
for (i = 0; i < nopers; i++)
{
forboth(l, opclass_lists[i], r, opstrat_lists[i])
{
Oid opclass = lfirst_oid(l);
int opstrat = lfirst_int(r);
if (opstrat == this_rctype &&
opclass_is_default(opclass))
ndefaults++;
}
}
if (ndefaults > best_defaults)
{
best_defaults = ndefaults;
rctype = this_rctype;
multiple_best = false;
}
else if (ndefaults == best_defaults)
multiple_best = true;
}
if (best_defaults == 0 || multiple_best)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("could not determine interpretation of row comparison operator %s",
strVal(llast(opname))),
errdetail("There are multiple equally-plausible candidates.")));
break;
}
}
/*
* For = and <> cases, we just combine the pairwise operators with
* AND or OR respectively.
*
* Note: this is presently the only place where the parser generates
* BoolExpr with more than two arguments. Should be OK since the
* rest of the system thinks BoolExpr is N-argument anyway.
*/
if (rctype == ROWCOMPARE_EQ)
return (Node *) makeBoolExpr(AND_EXPR, opexprs);
if (rctype == ROWCOMPARE_NE)
return (Node *) makeBoolExpr(OR_EXPR, opexprs);
/*
* Otherwise we need to determine exactly which opclass to associate
* with each operator.
*/
opclasses = NIL;
for (i = 0; i < nopers; i++)
{
Oid best_opclass = 0;
int ndefault = 0;
int nmatch = 0;
forboth(l, opclass_lists[i], r, opstrat_lists[i])
{
Oid opclass = lfirst_oid(l);
int opstrat = lfirst_int(r);
if (opstrat == rctype)
{
if (ndefault == 0)
best_opclass = opclass;
if (opclass_is_default(opclass))
ndefault++;
else
nmatch++;
}
}
if (ndefault == 1 || (ndefault == 0 && nmatch == 1))
opclasses = lappend_oid(opclasses, best_opclass);
else
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("could not determine interpretation of row comparison operator %s",
strVal(llast(opname))),
errdetail("There are multiple equally-plausible candidates.")));
}
/*
* Now deconstruct the OpExprs and create a RowCompareExpr.
*
* Note: can't just reuse the passed largs/rargs lists, because of
* possibility that make_op inserted coercion operations.
*/
opnos = NIL;
largs = NIL;
rargs = NIL;
foreach(l, opexprs)
{
OpExpr *cmp = (OpExpr *) lfirst(l);
opnos = lappend_oid(opnos, cmp->opno);
largs = lappend(largs, linitial(cmp->args));
rargs = lappend(rargs, lsecond(cmp->args));
}
rcexpr = makeNode(RowCompareExpr);
rcexpr->rctype = rctype;
rcexpr->opnos = opnos;
rcexpr->opclasses = opclasses;
rcexpr->largs = largs;
rcexpr->rargs = rargs;
return (Node *) rcexpr;
}
/*