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postgresql/src/backend/parser/parse_expr.c

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/*-------------------------------------------------------------------------
*
* parse_expr.c
* handle expressions in parser
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.122 2002/07/18 04:41:45 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/params.h"
#include "parser/analyze.h"
#include "parser/gramparse.h"
#include "parser/parse.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 "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
int max_expr_depth = DEFAULT_MAX_EXPR_DEPTH;
static int expr_depth_counter = 0;
bool Transform_null_equals = false;
static Node *parser_typecast_constant(Value *expr, TypeName *typename);
static Node *parser_typecast_expression(ParseState *pstate,
Node *expr, TypeName *typename);
static Node *transformColumnRef(ParseState *pstate, ColumnRef *cref);
static Node *transformIndirection(ParseState *pstate, Node *basenode,
List *indirection);
/*
* Initialize for parsing a new query.
*
* We reset the expression depth counter here, in case it was left nonzero
* due to elog()'ing out of the last parsing operation.
*/
void
parse_expr_init(void)
{
expr_depth_counter = 0;
}
/*
* 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.
*
* NOTE: there are various cases in which this routine will get applied to
* an already-transformed expression. An examples:
* - 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".
* While it might be possible to eliminate these cases, the path of
* least resistance so far has been to ensure that transformExpr() does
* no damage if applied to an already-transformed tree. This is pretty
* easy for cases where the transformation replaces one node type with
* another, such as A_Const => Const; we just do nothing when handed
* a Const. More care is needed for node types that are used as both
* input and output of transformExpr; see SubLink for example.
*/
Node *
transformExpr(ParseState *pstate, Node *expr)
{
Node *result = NULL;
if (expr == NULL)
return NULL;
/*
* Guard against an overly complex expression leading to coredump due
* to stack overflow here, or in later recursive routines that
* traverse expression trees. Note that this is very unlikely to
* happen except with pathological queries; but we don't want someone
* to be able to crash the backend quite that easily...
*/
if (++expr_depth_counter > max_expr_depth)
elog(ERROR, "Expression too complex: nesting depth exceeds max_expr_depth = %d",
max_expr_depth);
switch (nodeTag(expr))
{
case T_ColumnRef:
{
result = transformColumnRef(pstate, (ColumnRef *) expr);
break;
}
case T_ParamRef:
{
ParamRef *pref = (ParamRef *) expr;
int paramno = pref->number;
Oid paramtyp = param_type(paramno);
Param *param;
List *fields;
if (!OidIsValid(paramtyp))
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 = paramtyp;
result = (Node *) param;
/* handle qualification, if any */
foreach(fields, pref->fields)
{
result = ParseFuncOrColumn(pstate,
makeList1(lfirst(fields)),
makeList1(result),
false, false, true);
}
/* handle subscripts, if any */
result = transformIndirection(pstate, result,
pref->indirection);
break;
}
case T_A_Const:
{
A_Const *con = (A_Const *) expr;
Value *val = &con->val;
if (con->typename != NULL)
result = parser_typecast_constant(val, con->typename);
else
result = (Node *) make_const(val);
break;
}
case T_ExprFieldSelect:
{
ExprFieldSelect *efs = (ExprFieldSelect *) expr;
List *fields;
result = transformExpr(pstate, efs->arg);
/* handle qualification, if any */
foreach(fields, efs->fields)
{
result = ParseFuncOrColumn(pstate,
makeList1(lfirst(fields)),
makeList1(result),
false, false, true);
}
/* handle subscripts, if any */
result = transformIndirection(pstate, result,
efs->indirection);
break;
}
case T_TypeCast:
{
TypeCast *tc = (TypeCast *) expr;
Node *arg = transformExpr(pstate, tc->arg);
result = parser_typecast_expression(pstate, arg, tc->typename);
break;
}
case T_A_Expr:
{
A_Expr *a = (A_Expr *) expr;
switch (a->oper)
{
case OP:
{
/*
* Special-case "foo = NULL" and "NULL = foo"
* for compatibility with standards-broken
* products (like Microsoft's). Turn these
* into IS NULL exprs.
*/
if (Transform_null_equals &&
length(a->name) == 1 &&
strcmp(strVal(lfirst(a->name)), "=") == 0 &&
(exprIsNullConstant(a->lexpr) ||
exprIsNullConstant(a->rexpr)))
{
NullTest *n = makeNode(NullTest);
n->nulltesttype = IS_NULL;
if (exprIsNullConstant(a->lexpr))
n->arg = a->rexpr;
else
n->arg = a->lexpr;
result = transformExpr(pstate,
(Node *) n);
}
else
{
Node *lexpr = transformExpr(pstate,
a->lexpr);
Node *rexpr = transformExpr(pstate,
a->rexpr);
result = (Node *) make_op(a->name,
lexpr,
rexpr);
}
}
break;
case AND:
{
Node *lexpr = transformExpr(pstate,
a->lexpr);
Node *rexpr = transformExpr(pstate,
a->rexpr);
Expr *expr = makeNode(Expr);
lexpr = coerce_to_boolean(lexpr, "AND");
rexpr = coerce_to_boolean(rexpr, "AND");
expr->typeOid = BOOLOID;
expr->opType = AND_EXPR;
expr->args = makeList2(lexpr, rexpr);
result = (Node *) expr;
}
break;
case OR:
{
Node *lexpr = transformExpr(pstate,
a->lexpr);
Node *rexpr = transformExpr(pstate,
a->rexpr);
Expr *expr = makeNode(Expr);
lexpr = coerce_to_boolean(lexpr, "OR");
rexpr = coerce_to_boolean(rexpr, "OR");
expr->typeOid = BOOLOID;
expr->opType = OR_EXPR;
expr->args = makeList2(lexpr, rexpr);
result = (Node *) expr;
}
break;
case NOT:
{
Node *rexpr = transformExpr(pstate,
a->rexpr);
Expr *expr = makeNode(Expr);
rexpr = coerce_to_boolean(rexpr, "NOT");
expr->typeOid = BOOLOID;
expr->opType = NOT_EXPR;
expr->args = makeList1(rexpr);
result = (Node *) expr;
}
break;
case DISTINCT:
{
Node *lexpr = transformExpr(pstate,
a->lexpr);
Node *rexpr = transformExpr(pstate,
a->rexpr);
result = (Node *) make_op(a->name,
lexpr,
rexpr);
((Expr *)result)->opType = DISTINCT_EXPR;
}
}
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));
result = ParseFuncOrColumn(pstate,
fn->funcname,
fn->args,
fn->agg_star,
fn->agg_distinct,
false);
break;
}
case T_SubLink:
{
SubLink *sublink = (SubLink *) expr;
List *qtrees;
Query *qtree;
/* If we already transformed this node, do nothing */
if (IsA(sublink->subselect, Query))
{
result = expr;
break;
}
pstate->p_hasSubLinks = true;
qtrees = parse_analyze(sublink->subselect, pstate);
if (length(qtrees) != 1)
elog(ERROR, "Bad query in subselect");
qtree = (Query *) lfirst(qtrees);
if (qtree->commandType != CMD_SELECT ||
qtree->resultRelation != 0)
elog(ERROR, "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, "Subselect must have a field");
while ((tlist = lnext(tlist)) != NIL)
{
if (!((TargetEntry *) lfirst(tlist))->resdom->resjunk)
elog(ERROR, "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 */
List *left_list = sublink->lefthand;
List *right_list = qtree->targetList;
List *op;
char *opname;
List *elist;
foreach(elist, left_list)
lfirst(elist) = transformExpr(pstate, lfirst(elist));
Assert(IsA(sublink->oper, A_Expr));
op = ((A_Expr *) sublink->oper)->name;
opname = strVal(llast(op));
sublink->oper = NIL;
/* Combining operators other than =/<> is dubious... */
if (length(left_list) != 1 &&
strcmp(opname, "=") != 0 && strcmp(opname, "<>") != 0)
elog(ERROR, "Row comparison cannot use operator %s",
opname);
/*
* 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, "Subselect has too many fields");
lexpr = lfirst(left_list);
left_list = lnext(left_list);
/*
* 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(tent->expr),
false);
opform = (Form_pg_operator) GETSTRUCT(optup);
if (opform->oprresult != BOOLOID)
elog(ERROR, "%s has result type of %s, but must return %s"
" to be used with quantified predicate subquery",
opname, format_type_be(opform->oprresult),
format_type_be(BOOLOID));
if (get_func_retset(opform->oprcode))
elog(ERROR, "%s must not return a set"
" to be used with quantified predicate subquery",
opname);
newop = makeOper(oprid(optup), /* opno */
InvalidOid, /* opid */
opform->oprresult,
false);
sublink->oper = lappend(sublink->oper, newop);
ReleaseSysCache(optup);
}
if (left_list != NIL)
elog(ERROR, "Subselect has too few fields");
}
result = (Node *) expr;
break;
}
case T_CaseExpr:
{
CaseExpr *c = (CaseExpr *) expr;
CaseExpr *newc = makeNode(CaseExpr);
List *newargs = NIL;
List *typeids = NIL;
List *args;
Node *defresult;
Oid ptype;
/* transform the list of arguments */
foreach(args, c->args)
{
CaseWhen *w = (CaseWhen *) lfirst(args);
CaseWhen *neww = makeNode(CaseWhen);
Node *warg;
Assert(IsA(w, CaseWhen));
warg = w->expr;
if (c->arg != NULL)
{
/* shorthand form was specified, so expand... */
warg = (Node *) makeSimpleA_Expr(OP, "=",
c->arg, warg);
}
neww->expr = transformExpr(pstate, warg);
neww->expr = coerce_to_boolean(neww->expr, "CASE/WHEN");
/*
* result is NULL for NULLIF() construct - thomas
* 1998-11-11
*/
warg = w->result;
if (warg == NULL)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
warg = (Node *) n;
}
neww->result = transformExpr(pstate, warg);
newargs = lappend(newargs, neww);
typeids = lappendi(typeids, exprType(neww->result));
}
newc->args = newargs;
/*
* It's not shorthand anymore, so drop the implicit
* argument. This is necessary to keep any re-application
* of transformExpr from doing the wrong thing.
*/
newc->arg = NULL;
/* transform the default clause */
defresult = c->defresult;
if (defresult == NULL)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
defresult = (Node *) n;
}
newc->defresult = transformExpr(pstate, defresult);
/*
* Note: default result is considered the most significant
* type in determining preferred type. This is how the
* code worked before, but it seems a little bogus to me
* --- tgl
*/
typeids = lconsi(exprType(newc->defresult), typeids);
ptype = select_common_type(typeids, "CASE");
newc->casetype = ptype;
/* Convert default result clause, if necessary */
newc->defresult = coerce_to_common_type(pstate,
newc->defresult,
ptype,
"CASE/ELSE");
/* Convert when-clause results, if necessary */
foreach(args, newc->args)
{
CaseWhen *w = (CaseWhen *) lfirst(args);
w->result = coerce_to_common_type(pstate,
w->result,
ptype,
"CASE/WHEN");
}
result = (Node *) newc;
break;
}
case T_NullTest:
{
NullTest *n = (NullTest *) expr;
n->arg = transformExpr(pstate, n->arg);
/* the argument can be any type, so don't coerce it */
result = expr;
break;
}
case T_BooleanTest:
{
BooleanTest *b = (BooleanTest *) expr;
const char *clausename;
switch (b->booltesttype)
{
case IS_TRUE:
clausename = "IS TRUE";
break;
case IS_NOT_TRUE:
clausename = "IS NOT TRUE";
break;
case IS_FALSE:
clausename = "IS FALSE";
break;
case IS_NOT_FALSE:
clausename = "IS NOT FALSE";
break;
case IS_UNKNOWN:
clausename = "IS UNKNOWN";
break;
case IS_NOT_UNKNOWN:
clausename = "IS NOT UNKNOWN";
break;
default:
elog(ERROR, "transformExpr: unexpected booltesttype %d",
(int) b->booltesttype);
clausename = NULL; /* keep compiler quiet */
}
b->arg = transformExpr(pstate, b->arg);
b->arg = coerce_to_boolean(b->arg, clausename);
result = expr;
break;
}
case T_BetweenExpr:
{
BetweenExpr *b = (BetweenExpr *) expr;
List *typeIds = NIL;
HeapTuple tup;
Form_pg_operator opform;
/* Transform the expressions */
b->expr = transformExpr(pstate, b->expr);
b->lexpr = transformExpr(pstate, b->lexpr);
b->rexpr = transformExpr(pstate, b->rexpr);
/* Find coercion type for all 3 entities */
typeIds = lappendi(typeIds, exprType(b->expr));
typeIds = lappendi(typeIds, exprType(b->lexpr));
typeIds = lappendi(typeIds, exprType(b->rexpr));
b->typeId = select_common_type(typeIds, "TransformExpr");
/* Additional type information */
b->typeLen = get_typlen(b->typeId);
b->typeByVal = get_typbyval(b->typeId);
/* Coerce the three expressions to the type */
b->expr = coerce_to_common_type(pstate, b->expr,
b->typeId,
"TransformExpr");
b->lexpr = coerce_to_common_type(pstate, b->lexpr,
b->typeId,
"TransformExpr");
b->rexpr = coerce_to_common_type(pstate, b->rexpr,
b->typeId,
"TransformExpr");
/* Build the >= operator */
tup = oper(makeList1(makeString(">=")),
b->typeId, b->typeId, false);
opform = (Form_pg_operator) GETSTRUCT(tup);
/* Triple check our types */
if (b->typeId != opform->oprright || b->typeId != opform->oprleft)
elog(ERROR, "transformExpr: Unable to find appropriate"
" operator for between operation");
b->gthan = makeNode(Expr);
b->gthan->typeOid = opform->oprresult;
b->gthan->opType = OP_EXPR;
b->gthan->oper = (Node *) makeOper(oprid(tup), /* opno */
oprfuncid(tup), /* opid */
opform->oprresult, /* opresulttype */
get_func_retset(opform->oprcode));/* opretset */
ReleaseSysCache(tup);
/* Build the equation for <= operator */
tup = oper(makeList1(makeString("<=")),
b->typeId, b->typeId, false);
opform = (Form_pg_operator) GETSTRUCT(tup);
/* Triple check the types */
if (b->typeId != opform->oprright || b->typeId != opform->oprleft)
elog(ERROR, "transformExpr: Unable to find appropriate"
" operator for between operation");
b->lthan = makeNode(Expr);
b->lthan->typeOid = opform->oprresult;
b->lthan->opType = OP_EXPR;
b->lthan->oper = (Node *) makeOper(oprid(tup), /* opno */
oprfuncid(tup), /* opid */
opform->oprresult, /* opresulttype */
get_func_retset(opform->oprcode));/* opretset */
ReleaseSysCache(tup);
result = expr;
break;
}
/*
* Quietly accept node types that may be presented when we are
* called on an already-transformed tree.
*
* 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:
case T_FieldSelect:
case T_RelabelType:
{
result = (Node *) expr;
break;
}
default:
/* should not reach here */
elog(ERROR, "transformExpr: does not know how to transform node %d"
" (internal error)", nodeTag(expr));
break;
}
expr_depth_counter--;
return result;
}
static Node *
transformIndirection(ParseState *pstate, Node *basenode, List *indirection)
{
if (indirection == NIL)
return basenode;
return (Node *) transformArraySubscripts(pstate,
basenode, exprType(basenode),
indirection, false, NULL);
}
static Node *
transformColumnRef(ParseState *pstate, ColumnRef *cref)
{
int numnames = length(cref->fields);
Node *node;
RangeVar *rv;
/*----------
* The allowed syntaxes are:
*
* A First try to resolve as unqualified column name;
* if no luck, try to resolve as unqual. table name (A.*).
* A.B A is an unqual. table name; B is either a
* column or function name (trying column name first).
* A.B.C schema A, table B, col or func name C.
* A.B.C.D catalog A, schema B, table C, col or func D.
* A.* A is an unqual. table name; means whole-row value.
* A.B.* whole-row value of table B in schema A.
* A.B.C.* whole-row value of table C in schema B in catalog A.
*
* We do not need to cope with bare "*"; that will only be accepted by
* the grammar at the top level of a SELECT list, and transformTargetList
* will take care of it before it ever gets here.
*
* Currently, if a catalog name is given then it must equal the current
* database name; we check it here and then discard it.
*
* For whole-row references, the result is an untransformed RangeVar,
* which will work as the argument to a function call, but not in any
* other context at present. (We could instead coerce to a whole-row Var,
* but that will fail for subselect and join RTEs, because there is no
* pg_type entry for their rowtypes.)
*----------
*/
switch (numnames)
{
case 1:
{
char *name = strVal(lfirst(cref->fields));
/* Try to identify as an unqualified column */
node = colnameToVar(pstate, name);
if (node == NULL)
{
/*
* Not known as a column of any range-table entry, so
* try to find the name as a relation ... but not if
* subscripts appear. Note also that only relations
* already entered into the rangetable will be recognized.
*/
int levels_up;
if (cref->indirection == NIL &&
refnameRangeTblEntry(pstate, name, &levels_up) != NULL)
{
rv = makeNode(RangeVar);
rv->relname = name;
rv->inhOpt = INH_DEFAULT;
node = (Node *) rv;
}
else
elog(ERROR, "Attribute \"%s\" not found", name);
}
break;
}
case 2:
{
char *name1 = strVal(lfirst(cref->fields));
char *name2 = strVal(lsecond(cref->fields));
/* Whole-row reference? */
if (strcmp(name2, "*") == 0)
{
rv = makeNode(RangeVar);
rv->relname = name1;
rv->inhOpt = INH_DEFAULT;
node = (Node *) rv;
break;
}
/* Try to identify as a once-qualified column */
node = qualifiedNameToVar(pstate, name1, name2, true);
if (node == NULL)
{
/*
* Not known as a column of any range-table entry, so
* try it as a function call. Here, we will create an
* implicit RTE for tables not already entered.
*/
rv = makeNode(RangeVar);
rv->relname = name1;
rv->inhOpt = INH_DEFAULT;
node = ParseFuncOrColumn(pstate,
makeList1(makeString(name2)),
makeList1(rv),
false, false, true);
}
break;
}
case 3:
{
char *name1 = strVal(lfirst(cref->fields));
char *name2 = strVal(lsecond(cref->fields));
char *name3 = strVal(lfirst(lnext(lnext(cref->fields))));
/* Whole-row reference? */
if (strcmp(name3, "*") == 0)
{
rv = makeNode(RangeVar);
rv->schemaname = name1;
rv->relname = name2;
rv->inhOpt = INH_DEFAULT;
node = (Node *) rv;
break;
}
/* Try to identify as a twice-qualified column */
/* XXX do something with schema name here */
node = qualifiedNameToVar(pstate, name2, name3, true);
if (node == NULL)
{
/* Try it as a function call */
rv = makeNode(RangeVar);
rv->schemaname = name1;
rv->relname = name2;
rv->inhOpt = INH_DEFAULT;
node = ParseFuncOrColumn(pstate,
makeList1(makeString(name3)),
makeList1(rv),
false, false, true);
}
break;
}
case 4:
{
char *name1 = strVal(lfirst(cref->fields));
char *name2 = strVal(lsecond(cref->fields));
char *name3 = strVal(lfirst(lnext(lnext(cref->fields))));
char *name4 = strVal(lfirst(lnext(lnext(lnext(cref->fields)))));
/*
* We check the catalog name and then ignore it.
*/
if (strcmp(name1, DatabaseName) != 0)
elog(ERROR, "Cross-database references are not implemented");
/* Whole-row reference? */
if (strcmp(name4, "*") == 0)
{
rv = makeNode(RangeVar);
rv->schemaname = name2;
rv->relname = name3;
rv->inhOpt = INH_DEFAULT;
node = (Node *) rv;
break;
}
/* Try to identify as a twice-qualified column */
/* XXX do something with schema name here */
node = qualifiedNameToVar(pstate, name3, name4, true);
if (node == NULL)
{
/* Try it as a function call */
rv = makeNode(RangeVar);
rv->schemaname = name2;
rv->relname = name3;
rv->inhOpt = INH_DEFAULT;
node = ParseFuncOrColumn(pstate,
makeList1(makeString(name4)),
makeList1(rv),
false, false, true);
}
break;
}
default:
elog(ERROR, "Invalid qualified name syntax (too many names)");
node = NULL; /* keep compiler quiet */
break;
}
return transformIndirection(pstate, node, cref->indirection);
}
/*
* 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_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_FieldSelect:
type = ((FieldSelect *) expr)->resulttype;
break;
case T_RelabelType:
type = ((RelabelType *) expr)->resulttype;
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: Cannot 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_Constraint:
type = exprType(((Constraint *) expr)->raw_expr);
break;
case T_NullTest:
type = BOOLOID;
break;
case T_BooleanTest:
type = BOOLOID;
break;
case T_BetweenExpr:
type = BOOLOID;
break;
default:
elog(ERROR, "exprType: Do not 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;
case T_Expr:
{
int32 coercedTypmod;
/* Be smart about length-coercion functions... */
if (exprIsLengthCoercion(expr, &coercedTypmod))
return coercedTypmod;
}
break;
case T_FieldSelect:
return ((FieldSelect *) expr)->resulttypmod;
break;
case T_RelabelType:
return ((RelabelType *) expr)->resulttypmod;
break;
case T_CaseExpr:
{
/*
* If all the alternatives agree on type/typmod, return
* that typmod, else use -1
*/
CaseExpr *cexpr = (CaseExpr *) expr;
Oid casetype = cexpr->casetype;
int32 typmod;
List *arg;
if (!cexpr->defresult)
return -1;
if (exprType(cexpr->defresult) != casetype)
return -1;
typmod = exprTypmod(cexpr->defresult);
if (typmod < 0)
return -1; /* no point in trying harder */
foreach(arg, cexpr->args)
{
CaseWhen *w = (CaseWhen *) lfirst(arg);
Assert(IsA(w, CaseWhen));
if (exprType(w->result) != casetype)
return -1;
if (exprTypmod(w->result) != typmod)
return -1;
}
return typmod;
}
break;
default:
break;
}
return -1;
}
/*
* exprIsLengthCoercion
* Detect whether an expression tree is an application of a datatype's
* typmod-coercion function. Optionally extract the result's typmod.
*
* If coercedTypmod is not NULL, the typmod is stored there if the expression
* is a length-coercion function, else -1 is stored there.
*
* We assume that a two-argument function named for a datatype, whose
* output and first argument types are that datatype, and whose second
* input is an int32 constant, represents a forced length coercion.
*
* XXX It'd be better if the parsetree retained some explicit indication
* of the coercion, so we didn't need these heuristics.
*/
bool
exprIsLengthCoercion(Node *expr, int32 *coercedTypmod)
{
Func *func;
Const *second_arg;
HeapTuple procTuple;
HeapTuple typeTuple;
Form_pg_proc procStruct;
Form_pg_type typeStruct;
if (coercedTypmod != NULL)
*coercedTypmod = -1; /* default result on failure */
/* Is it a function-call at all? */
if (expr == NULL ||
!IsA(expr, Expr) ||
((Expr *) expr)->opType != FUNC_EXPR)
return false;
func = (Func *) (((Expr *) expr)->oper);
Assert(IsA(func, Func));
/*
* If it's not a two-argument function with the second argument being
* an int4 constant, it can't have been created from a length
* coercion.
*/
if (length(((Expr *) expr)->args) != 2)
return false;
second_arg = (Const *) lsecond(((Expr *) expr)->args);
if (!IsA(second_arg, Const) ||
second_arg->consttype != INT4OID ||
second_arg->constisnull)
return false;
/*
* Lookup the function in pg_proc
*/
procTuple = SearchSysCache(PROCOID,
ObjectIdGetDatum(func->funcid),
0, 0, 0);
if (!HeapTupleIsValid(procTuple))
elog(ERROR, "cache lookup for proc %u failed", func->funcid);
procStruct = (Form_pg_proc) GETSTRUCT(procTuple);
/*
* It must be a function with two arguments where the first is of the
* same type as the return value and the second is an int4. Also, just
* to be sure, check return type agrees with expr node.
*/
if (procStruct->pronargs != 2 ||
procStruct->prorettype != procStruct->proargtypes[0] ||
procStruct->proargtypes[1] != INT4OID ||
procStruct->prorettype != ((Expr *) expr)->typeOid)
{
ReleaseSysCache(procTuple);
return false;
}
/*
* Furthermore, the name and namespace of the function must be the same
* as its result type's name/namespace (cf. find_coercion_function).
*/
typeTuple = SearchSysCache(TYPEOID,
ObjectIdGetDatum(procStruct->prorettype),
0, 0, 0);
if (!HeapTupleIsValid(typeTuple))
elog(ERROR, "cache lookup for type %u failed",
procStruct->prorettype);
typeStruct = (Form_pg_type) GETSTRUCT(typeTuple);
if (strcmp(NameStr(procStruct->proname),
NameStr(typeStruct->typname)) != 0 ||
procStruct->pronamespace != typeStruct->typnamespace)
{
ReleaseSysCache(procTuple);
ReleaseSysCache(typeTuple);
return false;
}
/*
* OK, it is indeed a length-coercion function.
*/
if (coercedTypmod != NULL)
*coercedTypmod = DatumGetInt32(second_arg->constvalue);
ReleaseSysCache(procTuple);
ReleaseSysCache(typeTuple);
return true;
}
/*
* 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_constant(Value *expr, TypeName *typename)
{
Type tp;
Datum datum;
Const *con;
char *const_string = NULL;
bool string_palloced = false;
bool isNull = false;
tp = typenameType(typename);
switch (nodeTag(expr))
{
case T_Integer:
const_string = DatumGetCString(DirectFunctionCall1(int4out,
Int32GetDatum(expr->val.ival)));
string_palloced = true;
break;
case T_Float:
case T_String:
case T_BitString:
const_string = expr->val.str;
break;
case T_Null:
isNull = true;
break;
default:
elog(ERROR, "Cannot cast this expression to type '%s'",
typeTypeName(tp));
}
if (isNull)
datum = (Datum) NULL;
else
datum = stringTypeDatum(tp, const_string, typename->typmod);
con = makeConst(typeTypeId(tp),
typeLen(tp),
datum,
isNull,
typeByVal(tp),
false, /* not a set */
true /* is cast */ );
if (string_palloced)
pfree(const_string);
ReleaseSysCache(tp);
return (Node *) con;
}
/*
* Handle an explicit CAST applied to a non-constant expression.
* (Actually, this works for constants too, but gram.y won't generate
* a TypeCast node if the argument is just a constant.)
*
* The given expr has already been transformed, but we need to lookup
* the type name and then apply any necessary coercion function(s).
*/
static Node *
parser_typecast_expression(ParseState *pstate,
Node *expr, TypeName *typename)
{
Oid inputType = exprType(expr);
Oid targetType;
targetType = typenameTypeId(typename);
if (inputType == InvalidOid)
return expr; /* do nothing if NULL input */
if (inputType != targetType)
{
expr = CoerceTargetExpr(pstate, expr, inputType,
targetType, typename->typmod,
true); /* explicit coercion */
if (expr == NULL)
elog(ERROR, "Cannot cast type '%s' to '%s'",
format_type_be(inputType),
format_type_be(targetType));
}
/*
* If the target is a fixed-length type, it may need a length coercion
* as well as a type coercion.
*/
expr = coerce_type_typmod(pstate, expr,
targetType, typename->typmod);
return expr;
}
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