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Bruce Momjian authoredBruce Momjian authored
parse_clause.c 9.00 KiB
/*-------------------------------------------------------------------------
*
* parse_clause.c--
* handle clauses in parser
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.6 1997/12/29 04:31:31 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "postgres.h"
#include "access/heapam.h"
#include "catalog/pg_type.h"
#include "parser/analyze.h"
#include "parser/parse_clause.h"
#include "parser/parse_expr.h"
#include "parser/parse_node.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
static TargetEntry *find_targetlist_entry(ParseState *pstate,
SortGroupBy *sortgroupby, List *tlist);
static void parseFromClause(ParseState *pstate, List *frmList);
/*
* makeRangeTable -
* make a range table with the specified relation (optional) and the
* from-clause.
*/
void
makeRangeTable(ParseState *pstate, char *relname, List *frmList)
{
RangeTblEntry *rte;
parseFromClause(pstate, frmList);
if (relname == NULL)
return;
if (refnameRangeTablePosn(pstate->p_rtable, relname) < 1)
rte = addRangeTableEntry(pstate, relname, relname, FALSE, FALSE);
else
rte = refnameRangeTableEntry(pstate->p_rtable, relname);
pstate->p_target_rangetblentry = rte;
Assert(pstate->p_target_relation == NULL);
pstate->p_target_relation = heap_open(rte->relid);
Assert(pstate->p_target_relation != NULL);
/* will close relation later */
}
/*
* transformWhereClause -
* transforms the qualification and make sure it is of type Boolean
*
*/
Node *
transformWhereClause(ParseState *pstate, Node *a_expr)
{
Node *qual;
if (a_expr == NULL) return (Node *) NULL; /* no qualifiers */
pstate->p_in_where_clause = true;
qual = transformExpr(pstate, a_expr, EXPR_COLUMN_FIRST);
pstate->p_in_where_clause = false;
if (exprType(qual) != BOOLOID)
{
elog(WARN,
"where clause must return type bool, not %s",
typeidTypeName(exprType(qual)));
}
return qual;
}
/*
* parseFromClause -
* turns the table references specified in the from-clause into a
* range table. The range table may grow as we transform the expressions
* in the target list. (Note that this happens because in POSTQUEL, we
* allow references to relations not specified in the from-clause. We
* also allow that in our POST-SQL)
*
*/
static void
parseFromClause(ParseState *pstate, List *frmList)
{
List *fl;
foreach(fl, frmList)
{
RangeVar *r = lfirst(fl);
RelExpr *baserel = r->relExpr;
char *relname = baserel->relname;
char *refname = r->name;
RangeTblEntry *rte;
if (refname == NULL)
refname = relname;
/*
* marks this entry to indicate it comes from the FROM clause. In
* SQL, the target list can only refer to range variables
* specified in the from clause but we follow the more powerful
* POSTQUEL semantics and automatically generate the range
* variable if not specified. However there are times we need to
* know whether the entries are legitimate.
*
* eg. select * from foo f where f.x = 1; will generate wrong answer
* if we expand * to foo.x.
*/
rte = addRangeTableEntry(pstate, relname, refname, baserel->inh, TRUE);
}
}
/*
* find_targetlist_entry -
* returns the Resdom in the target list matching the specified varname
* and range
*
*/
static TargetEntry *
find_targetlist_entry(ParseState *pstate, SortGroupBy *sortgroupby, List *tlist)
{
List *i;
int real_rtable_pos = 0,
target_pos = 0;
TargetEntry *target_result = NULL;
if (sortgroupby->range)
real_rtable_pos = refnameRangeTablePosn(pstate->p_rtable, sortgroupby->range);
foreach(i, tlist)
{
TargetEntry *target = (TargetEntry *) lfirst(i);
Resdom *resnode = target->resdom;
Var *var = (Var *) target->expr;
char *resname = resnode->resname;
int test_rtable_pos = var->varno;
#ifdef PARSEDEBUG
printf("find_targetlist_entry- target name is %s, position %d, resno %d\n",
(sortgroupby->name ? sortgroupby->name : "(null)"), target_pos + 1, sortgroupby->resno);
#endif
if (!sortgroupby->name)
{
if (sortgroupby->resno == ++target_pos)
{
target_result = target;
break;
}
}
else
{
if (!strcmp(resname, sortgroupby->name))
{
if (sortgroupby->range)
{
if (real_rtable_pos == test_rtable_pos)
{
if (target_result != NULL)
elog(WARN, "Order/Group By '%s' is ambiguous", sortgroupby->name);
else
target_result = target;
}
}
else
{
if (target_result != NULL)
elog(WARN, "Order/Group By '%s' is ambiguous", sortgroupby->name);
else
target_result = target;
}
}
}
}
return target_result;
}
/*
* transformGroupClause -
* transform a Group By clause
*
*/
List *
transformGroupClause(ParseState *pstate, List *grouplist, List *targetlist)
{
List *glist = NIL,
*gl = NIL;
while (grouplist != NIL)
{
GroupClause *grpcl = makeNode(GroupClause);
TargetEntry *restarget;
Resdom *resdom;
restarget = find_targetlist_entry(pstate, lfirst(grouplist), targetlist);
if (restarget == NULL) elog(WARN, "The field being grouped by must appear in the target list");
grpcl->entry = restarget;
resdom = restarget->resdom;
grpcl->grpOpoid = oprid(oper("<",
resdom->restype,
resdom->restype, false));
if (glist == NIL)
gl = glist = lcons(grpcl, NIL);
else
{
List *i;
foreach (i, glist)
{
GroupClause *gcl = (GroupClause *) lfirst (i);
if ( gcl->entry == grpcl->entry )
break;
}
if ( i == NIL ) /* not in grouplist already */
{
lnext(gl) = lcons(grpcl, NIL);
gl = lnext(gl);
}
else
pfree (grpcl); /* get rid of this */
}
grouplist = lnext(grouplist);
}
return glist;
}
/*
* transformSortClause -
* transform an Order By clause
*
*/
List *
transformSortClause(ParseState *pstate,
List *orderlist,
List *sortlist,
List *targetlist,
char *uniqueFlag)
{
List *s = NIL;
while (orderlist != NIL)
{
SortGroupBy *sortby = lfirst(orderlist);
SortClause *sortcl = makeNode(SortClause);
TargetEntry *restarget;
Resdom *resdom;
sortlist = NIL; /* we create it on the fly here */
restarget = find_targetlist_entry(pstate, sortby, targetlist);
if (restarget == NULL)
elog(WARN, "The field being ordered by must appear in the target list");
sortcl->resdom = resdom = restarget->resdom;
sortcl->opoid = oprid(oper(sortby->useOp,
resdom->restype,
resdom->restype, false));
if (sortlist == NIL)
{
s = sortlist = lcons(sortcl, NIL);
}
else {
List *i;
foreach (i, sortlist)
{
SortClause *scl = (SortClause *) lfirst (i);
if ( scl->resdom == sortcl->resdom )
break;
}
if ( i == NIL ) /* not in sortlist already */
{
lnext(s) = lcons(sortcl, NIL);
s = lnext(s);
}
else
pfree (sortcl); /* get rid of this */
}
orderlist = lnext(orderlist);
}
if (uniqueFlag)
{
List *i;
if (uniqueFlag[0] == '*')
{
/*
* concatenate all elements from target list that are not
* already in the sortby list
*/
foreach(i, targetlist)
{
TargetEntry *tlelt = (TargetEntry *) lfirst(i);
s = sortlist;
while (s != NIL)
{
SortClause *sortcl = lfirst(s);
if (sortcl->resdom == tlelt->resdom)
break;
s = lnext(s);
}
if (s == NIL)
{
/* not a member of the sortclauses yet */
SortClause *sortcl = makeNode(SortClause);
sortcl->resdom = tlelt->resdom;
sortcl->opoid = any_ordering_op(tlelt->resdom->restype);
sortlist = lappend(sortlist, sortcl);
}
}
}
else
{
TargetEntry *tlelt = NULL;
char *uniqueAttrName = uniqueFlag;
/* only create sort clause with the specified unique attribute */
foreach(i, targetlist)
{
tlelt = (TargetEntry *) lfirst(i);
if (strcmp(tlelt->resdom->resname, uniqueAttrName) == 0)
break;
}
if (i == NIL) {
elog(WARN, "The field specified in the UNIQUE ON clause is not in the targetlist");
}
s = sortlist;
foreach(s, sortlist)
{
SortClause *sortcl = lfirst(s);
if (sortcl->resdom == tlelt->resdom)
break;
}
if (s == NIL)
{
/* not a member of the sortclauses yet */
SortClause *sortcl = makeNode(SortClause);
sortcl->resdom = tlelt->resdom;
sortcl->opoid = any_ordering_op(tlelt->resdom->restype);
sortlist = lappend(sortlist, sortcl);
}
}
}
return sortlist;
}
/*
* transformUnionClause -
* transform a Union clause
*
*/
List *
transformUnionClause(List *unionClause, List *targetlist)
{
List *union_list = NIL;
QueryTreeList *qlist;
int i;
if (unionClause)
{
qlist = parse_analyze(unionClause);
for (i=0; i < qlist->len; i++)
union_list = lappend(union_list, qlist->qtrees[i]);
/* we need to check return types are consistent here */
return union_list;
}
else
return NIL;
}