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postgres/src/backend/parser/parse_expr.c
Bruce Momjian cf374febf5 >Turning nextval and currval into keywords is not an acceptable way to 
>go about this.  That will risk breaking existing applications that use
>those names as column names.
>
>It should actually almost work to write sq.nextval as things stand,
>because Postgres has for a long time considered table.function and
>function(table) to be interchangeable notations for certain kinds of
>functions.  nextval doesn't seem to be one of that kind of function,
>at the moment.  I'd suggest leaving the grammar as it was, and taking a
>look at ParseFuncOrColumn in parse_func.c to see if you can't persuade
>it to accept the sequence functions in that style.

OK, good point. I tried to implement it somewhere else and ended up
extending transformAttr. Attached you'll find the patch.

Jeroen van Vianen
1999-12-16 20:07:41 +00:00

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/*-------------------------------------------------------------------------
*
* parse_expr.c
* handle expressions in parser
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.61 1999/12/16 20:07:41 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "catalog/pg_operator.h"
#include "nodes/makefuncs.h"
#include "nodes/params.h"
#include "nodes/relation.h"
#include "parse.h"
#include "parser/analyze.h"
#include "parser/gramparse.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "utils/builtins.h"
static Node *parser_typecast(Value *expr, TypeName *typename, int32 atttypmod);
static Node *transformAttr(ParseState *pstate, Attr *att, int precedence);
static Node *transformIdent(ParseState *pstate, Ident *ident, int precedence);
static Node *transformIndirection(ParseState *pstate, Node *basenode,
List *indirection);
/*
* transformExpr -
* analyze and transform expressions. Type checking and type casting is
* done here. The optimizer and the executor cannot handle the original
* (raw) expressions collected by the parse tree. Hence the transformation
* here.
*/
Node *
transformExpr(ParseState *pstate, Node *expr, int precedence)
{
Node *result = NULL;
if (expr == NULL)
return NULL;
switch (nodeTag(expr))
{
case T_Attr:
{
result = transformAttr(pstate, (Attr *) expr, precedence);
break;
}
case T_A_Const:
{
A_Const *con = (A_Const *) expr;
Value *val = &con->val;
if (con->typename != NULL)
result = parser_typecast(val, con->typename, -1);
else
result = (Node *) make_const(val);
break;
}
case T_ParamNo:
{
ParamNo *pno = (ParamNo *) expr;
int paramno = pno->number;
Oid toid = param_type(paramno);
Param *param;
if (!OidIsValid(toid))
elog(ERROR, "Parameter '$%d' is out of range", paramno);
param = makeNode(Param);
param->paramkind = PARAM_NUM;
param->paramid = (AttrNumber) paramno;
param->paramname = "<unnamed>";
param->paramtype = (Oid) toid;
param->param_tlist = (List *) NULL;
result = transformIndirection(pstate, (Node *) param,
pno->indirection);
break;
}
case T_A_Expr:
{
A_Expr *a = (A_Expr *) expr;
switch (a->oper)
{
case OP:
{
Node *lexpr = transformExpr(pstate, a->lexpr, precedence);
Node *rexpr = transformExpr(pstate, a->rexpr, precedence);
result = (Node *) make_op(a->opname, lexpr, rexpr);
}
break;
case ISNULL:
{
Node *lexpr = transformExpr(pstate, a->lexpr, precedence);
result = ParseFuncOrColumn(pstate,
"nullvalue",
lcons(lexpr, NIL),
false, false,
&pstate->p_last_resno,
precedence);
}
break;
case NOTNULL:
{
Node *lexpr = transformExpr(pstate, a->lexpr, precedence);
result = ParseFuncOrColumn(pstate,
"nonnullvalue",
lcons(lexpr, NIL),
false, false,
&pstate->p_last_resno,
precedence);
}
break;
case AND:
{
Expr *expr = makeNode(Expr);
Node *lexpr = transformExpr(pstate, a->lexpr, precedence);
Node *rexpr = transformExpr(pstate, a->rexpr, precedence);
if (exprType(lexpr) != BOOLOID)
elog(ERROR, "left-hand side of AND is type '%s', not bool",
typeidTypeName(exprType(lexpr)));
if (exprType(rexpr) != BOOLOID)
elog(ERROR, "right-hand side of AND is type '%s', not bool",
typeidTypeName(exprType(rexpr)));
expr->typeOid = BOOLOID;
expr->opType = AND_EXPR;
expr->args = makeList(lexpr, rexpr, -1);
result = (Node *) expr;
}
break;
case OR:
{
Expr *expr = makeNode(Expr);
Node *lexpr = transformExpr(pstate, a->lexpr, precedence);
Node *rexpr = transformExpr(pstate, a->rexpr, precedence);
if (exprType(lexpr) != BOOLOID)
elog(ERROR, "left-hand side of OR is type '%s', not bool",
typeidTypeName(exprType(lexpr)));
if (exprType(rexpr) != BOOLOID)
elog(ERROR, "right-hand side of OR is type '%s', not bool",
typeidTypeName(exprType(rexpr)));
expr->typeOid = BOOLOID;
expr->opType = OR_EXPR;
expr->args = makeList(lexpr, rexpr, -1);
result = (Node *) expr;
}
break;
case NOT:
{
Expr *expr = makeNode(Expr);
Node *rexpr = transformExpr(pstate, a->rexpr, precedence);
if (exprType(rexpr) != BOOLOID)
elog(ERROR, "argument to NOT is type '%s', not bool",
typeidTypeName(exprType(rexpr)));
expr->typeOid = BOOLOID;
expr->opType = NOT_EXPR;
expr->args = makeList(rexpr, -1);
result = (Node *) expr;
}
break;
}
break;
}
case T_Ident:
{
result = transformIdent(pstate, (Ident *) expr, precedence);
break;
}
case T_FuncCall:
{
FuncCall *fn = (FuncCall *) expr;
List *args;
/* transform the list of arguments */
foreach(args, fn->args)
lfirst(args) = transformExpr(pstate, (Node *) lfirst(args), precedence);
result = ParseFuncOrColumn(pstate,
fn->funcname,
fn->args,
fn->agg_star,
fn->agg_distinct,
&pstate->p_last_resno,
precedence);
break;
}
case T_SubLink:
{
SubLink *sublink = (SubLink *) expr;
List *qtrees;
Query *qtree;
pstate->p_hasSubLinks = true;
qtrees = parse_analyze(lcons(sublink->subselect, NIL), pstate);
if (length(qtrees) != 1)
elog(ERROR, "parser: bad query in subselect");
qtree = (Query *) lfirst(qtrees);
if (qtree->commandType != CMD_SELECT ||
qtree->resultRelation != 0)
elog(ERROR, "parser: bad query in subselect");
sublink->subselect = (Node *) qtree;
if (sublink->subLinkType == EXISTS_SUBLINK)
{
/* EXISTS needs no lefthand or combining operator.
* These fields should be NIL already, but make sure.
*/
sublink->lefthand = NIL;
sublink->oper = NIL;
}
else if (sublink->subLinkType == EXPR_SUBLINK)
{
List *tlist = qtree->targetList;
/* Make sure the subselect delivers a single column
* (ignoring resjunk targets).
*/
if (tlist == NIL ||
((TargetEntry *) lfirst(tlist))->resdom->resjunk)
elog(ERROR, "parser: subselect must have a field");
while ((tlist = lnext(tlist)) != NIL)
{
if (! ((TargetEntry *) lfirst(tlist))->resdom->resjunk)
elog(ERROR, "parser: subselect must have only one field");
}
/* EXPR needs no lefthand or combining operator.
* These fields should be NIL already, but make sure.
*/
sublink->lefthand = NIL;
sublink->oper = NIL;
}
else
{
/* ALL, ANY, or MULTIEXPR: generate operator list */
char *op = lfirst(sublink->oper);
List *left_list = sublink->lefthand;
List *right_list = qtree->targetList;
List *elist;
foreach(elist, left_list)
lfirst(elist) = transformExpr(pstate, lfirst(elist),
precedence);
/* Combining operators other than =/<> is dubious... */
if (length(left_list) != 1 &&
strcmp(op, "=") != 0 && strcmp(op, "<>") != 0)
elog(ERROR, "parser: '%s' is not usable for row comparison",
op);
sublink->oper = NIL;
/* 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.
*/
while (right_list != NIL)
{
TargetEntry *tent = (TargetEntry *) lfirst(right_list);
Node *lexpr;
Operator optup;
Form_pg_operator opform;
Oper *newop;
right_list = lnext(right_list);
if (tent->resdom->resjunk)
continue;
if (left_list == NIL)
elog(ERROR, "parser: Subselect has too many fields.");
lexpr = lfirst(left_list);
left_list = lnext(left_list);
optup = oper(op,
exprType(lexpr),
exprType(tent->expr),
FALSE);
opform = (Form_pg_operator) GETSTRUCT(optup);
if (opform->oprresult != BOOLOID)
elog(ERROR, "parser: '%s' must return 'bool' to be used with quantified predicate subquery", op);
newop = makeOper(oprid(optup),/* opno */
InvalidOid, /* opid */
opform->oprresult,
0,
NULL);
sublink->oper = lappend(sublink->oper, newop);
}
if (left_list != NIL)
elog(ERROR, "parser: Subselect has too few fields.");
}
result = (Node *) expr;
break;
}
case T_CaseExpr:
{
CaseExpr *c = (CaseExpr *) expr;
CaseWhen *w;
List *args;
Oid ptype;
CATEGORY pcategory;
/* transform the list of arguments */
foreach(args, c->args)
{
w = lfirst(args);
if (c->arg != NULL)
{
/* shorthand form was specified, so expand... */
A_Expr *a = makeNode(A_Expr);
a->oper = OP;
a->opname = "=";
a->lexpr = c->arg;
a->rexpr = w->expr;
w->expr = (Node *) a;
}
lfirst(args) = transformExpr(pstate, (Node *) w, precedence);
}
/*
* It's not shorthand anymore, so drop the implicit
* argument. This is necessary to keep the executor from
* seeing an untransformed expression...
*/
c->arg = NULL;
/* transform the default clause */
if (c->defresult == NULL)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
c->defresult = (Node *) n;
}
c->defresult = transformExpr(pstate, (Node *) c->defresult, precedence);
/* now check types across result clauses... */
c->casetype = exprType(c->defresult);
ptype = c->casetype;
pcategory = TypeCategory(ptype);
foreach(args, c->args)
{
Oid wtype;
w = lfirst(args);
wtype = exprType(w->result);
/* move on to next one if no new information... */
if (wtype && (wtype != UNKNOWNOID)
&& (wtype != ptype))
{
/* so far, only nulls so take anything... */
if (!ptype)
{
ptype = wtype;
pcategory = TypeCategory(ptype);
}
/*
* both types in different categories? then not
* much hope...
*/
else if ((TypeCategory(wtype) != pcategory)
|| ((TypeCategory(wtype) == USER_TYPE)
&& (TypeCategory(c->casetype) == USER_TYPE)))
{
elog(ERROR, "CASE/WHEN types '%s' and '%s' not matched",
typeidTypeName(c->casetype), typeidTypeName(wtype));
}
/*
* new one is preferred and can convert? then take
* it...
*/
else if (IsPreferredType(pcategory, wtype)
&& can_coerce_type(1, &ptype, &wtype))
{
ptype = wtype;
pcategory = TypeCategory(ptype);
}
}
}
/* Convert default result clause, if necessary */
if (c->casetype != ptype)
{
if (!c->casetype)
{
/*
* default clause is NULL, so assign preferred
* type from WHEN clauses...
*/
c->casetype = ptype;
}
else if (can_coerce_type(1, &c->casetype, &ptype))
{
c->defresult = coerce_type(pstate, c->defresult,
c->casetype, ptype, -1);
c->casetype = ptype;
}
else
{
elog(ERROR, "CASE/ELSE unable to convert to type %s",
typeidTypeName(ptype));
}
}
/* Convert when clauses, if not null and if necessary */
foreach(args, c->args)
{
Oid wtype;
w = lfirst(args);
wtype = exprType(w->result);
/*
* only bother with conversion if not NULL and
* different type...
*/
if (wtype && (wtype != UNKNOWNOID)
&& (wtype != ptype))
{
if (can_coerce_type(1, &wtype, &ptype))
{
w->result = coerce_type(pstate, w->result, wtype,
ptype, -1);
}
else
{
elog(ERROR, "CASE/WHEN unable to convert to type %s",
typeidTypeName(ptype));
}
}
}
result = expr;
break;
}
case T_CaseWhen:
{
CaseWhen *w = (CaseWhen *) expr;
w->expr = transformExpr(pstate, (Node *) w->expr, precedence);
if (exprType(w->expr) != BOOLOID)
elog(ERROR, "WHEN clause must have a boolean result");
/*
* result is NULL for NULLIF() construct - thomas
* 1998-11-11
*/
if (w->result == NULL)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
w->result = (Node *) n;
}
w->result = transformExpr(pstate, (Node *) w->result, precedence);
result = expr;
break;
}
/* Some nodes do _not_ come from the original parse tree,
* but result from parser transformation in this phase.
* At least one construct (BETWEEN/AND) puts the same nodes
* into two branches of the parse tree; hence, some nodes
* are transformed twice.
* Another way it can happen is that coercion of an operator or
* function argument to the required type (via coerce_type())
* can apply transformExpr to an already-transformed subexpression.
* An example here is "SELECT count(*) + 1.0 FROM table".
* Thus, we can see node types in this routine that do not appear in the
* original parse tree. Assume they are already transformed, and just
* pass them through.
* Do any other node types need to be accepted? For now we are taking
* a conservative approach, and only accepting node types that are
* demonstrably necessary to accept.
*/
case T_Expr:
case T_Var:
case T_Const:
case T_Param:
case T_Aggref:
case T_ArrayRef:
{
result = (Node *) expr;
break;
}
default:
/* should not reach here */
elog(ERROR, "transformExpr: does not know how to transform node %d",
nodeTag(expr));
break;
}
return result;
}
static Node *
transformIndirection(ParseState *pstate, Node *basenode, List *indirection)
{
if (indirection == NIL)
return basenode;
return (Node *) transformArraySubscripts(pstate, basenode,
indirection, false, NULL);
}
static Node *
transformAttr(ParseState *pstate, Attr *att, int precedence)
{
Node *basenode;
char * attribute;
/* Get the name of the first attribute */
if ((att != NULL) && (lfirst(att->attrs) != NULL))
{
/*
* Special case for name.nextval and name.currval, assume it's a
* sequence and transform to function call to nextval('name') and
* currval('name')
*/
attribute = pstrdup(((Value *) lfirst(att->attrs))->val.str);
if ((strcasecmp(attribute, "nextval") == 0) ||
(strcasecmp(attribute, "currval") == 0))
{
Value *s = makeNode(Value);
s->type = T_String;
s->val.str = att->relname;
return ParseFuncOrColumn(pstate, attribute,
lcons(make_const(s), NIL), false, false,
&pstate->p_last_resno, precedence);
}
}
basenode = ParseNestedFuncOrColumn(pstate, att, &pstate->p_last_resno,
precedence);
return transformIndirection(pstate, basenode, att->indirection);
}
static Node *
transformIdent(ParseState *pstate, Ident *ident, int precedence)
{
Node *result = NULL;
RangeTblEntry *rte;
/* try to find the ident as a relation ... but not if subscripts appear */
if (ident->indirection == NIL &&
refnameRangeTableEntry(pstate, ident->name) != NULL)
{
ident->isRel = TRUE;
result = (Node *) ident;
}
if (result == NULL || precedence == EXPR_COLUMN_FIRST)
{
/* try to find the ident as a column */
if ((rte = colnameRangeTableEntry(pstate, ident->name)) != NULL)
{
/* Convert it to a fully qualified Attr, and transform that */
Attr *att = makeNode(Attr);
att->relname = rte->refname;
att->paramNo = NULL;
att->attrs = lcons(makeString(ident->name), NIL);
att->indirection = ident->indirection;
return transformAttr(pstate, att, precedence);
}
}
if (result == NULL)
elog(ERROR, "attribute '%s' not found", ident->name);
return result;
}
/*
* exprType -
* returns the Oid of the type of the expression. (Used for typechecking.)
*/
Oid
exprType(Node *expr)
{
Oid type = (Oid) InvalidOid;
if (!expr)
return type;
switch (nodeTag(expr))
{
case T_Func:
type = ((Func *) expr)->functype;
break;
case T_Iter:
type = ((Iter *) expr)->itertype;
break;
case T_Var:
type = ((Var *) expr)->vartype;
break;
case T_Expr:
type = ((Expr *) expr)->typeOid;
break;
case T_Const:
type = ((Const *) expr)->consttype;
break;
case T_ArrayRef:
type = ((ArrayRef *) expr)->refelemtype;
break;
case T_Aggref:
type = ((Aggref *) expr)->aggtype;
break;
case T_Param:
type = ((Param *) expr)->paramtype;
break;
case T_SubLink:
{
SubLink *sublink = (SubLink *) expr;
if (sublink->subLinkType == EXPR_SUBLINK)
{
/* get the type of the subselect's first target column */
Query *qtree = (Query *) sublink->subselect;
TargetEntry *tent;
if (! qtree || ! IsA(qtree, Query))
elog(ERROR, "exprType: can't get type for untransformed sublink");
tent = (TargetEntry *) lfirst(qtree->targetList);
type = tent->resdom->restype;
}
else
{
/* for all other sublink types, result is boolean */
type = BOOLOID;
}
}
break;
case T_CaseExpr:
type = ((CaseExpr *) expr)->casetype;
break;
case T_CaseWhen:
type = exprType(((CaseWhen *) expr)->result);
break;
case T_Ident:
/* is this right? */
type = UNKNOWNOID;
break;
default:
elog(ERROR, "exprType: don't know how to get type for %d node",
nodeTag(expr));
break;
}
return type;
}
/*
* exprTypmod -
* returns the type-specific attrmod of the expression, if it can be
* determined. In most cases, it can't and we return -1.
*/
int32
exprTypmod(Node *expr)
{
if (!expr)
return -1;
switch (nodeTag(expr))
{
case T_Var:
return ((Var *) expr)->vartypmod;
case T_Const:
{
/* Be smart about string constants... */
Const *con = (Const *) expr;
switch (con->consttype)
{
case BPCHAROID:
if (! con->constisnull)
return VARSIZE(DatumGetPointer(con->constvalue));
break;
default:
break;
}
}
break;
default:
break;
}
return -1;
}
/*
* Produce an appropriate Const node from a constant value produced
* by the parser and an explicit type name to cast to.
*/
static Node *
parser_typecast(Value *expr, TypeName *typename, int32 atttypmod)
{
Const *adt;
Datum lcp;
Type tp;
char *const_string = NULL;
bool string_palloced = false;
switch (nodeTag(expr))
{
case T_String:
const_string = DatumGetPointer(expr->val.str);
break;
case T_Integer:
string_palloced = true;
const_string = int4out(expr->val.ival);
break;
case T_Float:
string_palloced = true;
const_string = float8out(&expr->val.dval);
break;
default:
elog(ERROR,
"parser_typecast: cannot cast this expression to type '%s'",
typename->name);
}
if (typename->arrayBounds != NIL)
{
char type_string[NAMEDATALEN+2];
sprintf(type_string, "_%s", typename->name);
tp = (Type) typenameType(type_string);
}
else
tp = (Type) typenameType(typename->name);
lcp = stringTypeDatum(tp, const_string, atttypmod);
adt = makeConst(typeTypeId(tp),
typeLen(tp),
(Datum) lcp,
false,
typeByVal(tp),
false, /* not a set */
true /* is cast */ );
if (string_palloced)
pfree(const_string);
return (Node *) adt;
}
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