/*-------------------------------------------------------------------------
*
* 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 1.49 2000/01/17 02:04:16 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "optimizer/tlist.h"
#include "parse.h"
#include "parser/parse_clause.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#define ORDER_CLAUSE 0
#define GROUP_CLAUSE 1
static char *clauseText[] = {"ORDER", "GROUP"};
static TargetEntry *findTargetlistEntry(ParseState *pstate, Node *node,
List *tlist, int clause,
char *uniqFlag);
static void parseFromClause(ParseState *pstate, List *frmList, Node **qual);
static char *transformTableEntry(ParseState *pstate, RangeVar *r);
static List *addTargetToSortList(TargetEntry *tle, List *sortlist,
List *targetlist, char *opname);
static bool exprIsInSortList(Node *expr, List *sortList, List *targetList);
#ifdef ENABLE_OUTER_JOINS
static Node *transformUsingClause(ParseState *pstate, List *onList,
char *lname, char *rname);
#endif
/*
* makeRangeTable -
* Build the initial range table from the FROM clause.
*/
void
makeRangeTable(ParseState *pstate, List *frmList, Node **qual)
{
/* Currently, nothing to do except this: */
parseFromClause(pstate, frmList, qual);
}
/*
* setTargetTable
* Add the target relation of INSERT or UPDATE to the range table,
* and make the special links to it in the ParseState.
*
* Note that the target is not marked as either inFromCl or inJoinSet.
* For INSERT, we don't want the target to be joined to; it's a
* destination of tuples, not a source. For UPDATE/DELETE, we do
* need to scan or join the target. This will happen without the
* inJoinSet flag because the planner's preprocess_targetlist()
* adds the destination's CTID attribute to the targetlist, and
* therefore the destination will be a referenced table even if
* there is no other use of any of its attributes. Tricky, eh?
*/
void
setTargetTable(ParseState *pstate, char *relname)
{
RangeTblEntry *rte;
int sublevels_up;
if ((refnameRangeTablePosn(pstate, relname, &sublevels_up) == 0)
|| (sublevels_up != 0))
rte = addRangeTableEntry(pstate, relname, relname,
FALSE, FALSE, FALSE);
else
rte = refnameRangeTableEntry(pstate, relname);
/* This could only happen for multi-action rules */
if (pstate->p_target_relation != NULL)
heap_close(pstate->p_target_relation, AccessShareLock);
pstate->p_target_rangetblentry = rte;
pstate->p_target_relation = heap_open(rte->relid, AccessShareLock);
/* will close relation later, see analyze.c */
}
/*
* transformWhereClause -
* transforms the qualification and make sure it is of type Boolean
*
* Now accept an additional argument, which is a qualification derived
* from the JOIN/ON or JOIN/USING syntax.
* - thomas 1998-12-16
*/
Node *
transformWhereClause(ParseState *pstate, Node *a_expr, Node *o_expr)
{
A_Expr *expr;
Node *qual;
if ((a_expr == NULL) && (o_expr == NULL))
return NULL; /* no qualifiers */
if ((a_expr != NULL) && (o_expr != NULL))
{
A_Expr *a = makeNode(A_Expr);
a->oper = AND;
a->opname = NULL;
a->lexpr = o_expr;
a->rexpr = a_expr;
expr = a;
}
else if (o_expr != NULL)
expr = (A_Expr *) o_expr;
else
expr = (A_Expr *) a_expr;
pstate->p_in_where_clause = true;
qual = transformExpr(pstate, (Node *) expr, EXPR_COLUMN_FIRST);
pstate->p_in_where_clause = false;
if (exprType(qual) != BOOLOID)
{
elog(ERROR, "WHERE clause must return type bool, not type %s",
typeidTypeName(exprType(qual)));
}
return qual;
}
#ifdef ENABLE_OUTER_JOINS
static Attr *
makeAttr(char *relname, char *attname)
{
Attr *a = makeNode(Attr);
a->relname = relname;
a->paramNo = NULL;
a->attrs = lcons(makeString(attname), NIL);
a->indirection = NULL;
return a;
}
#endif
#ifdef ENABLE_OUTER_JOINS
/* transformUsingClause()
* Take an ON or USING clause from a join expression and expand if necessary.
*/
static Node *
transformUsingClause(ParseState *pstate, List *onList, char *lname, char *rname)
{
A_Expr *expr = NULL;
List *on;
Node *qual;
foreach(on, onList)
{
qual = lfirst(on);
/*
* Ident node means it is just a column name from a real USING
* clause...
*/
if (IsA(qual, Ident))
{
Ident *i = (Ident *) qual;
Attr *lattr = makeAttr(lname, i->name);
Attr *rattr = makeAttr(rname, i->name);
A_Expr *e = makeNode(A_Expr);
e->oper = OP;
e->opname = "=";
e->lexpr = (Node *) lattr;
e->rexpr = (Node *) rattr;
if (expr != NULL)
{
A_Expr *a = makeNode(A_Expr);
a->oper = AND;
a->opname = NULL;
a->lexpr = (Node *) expr;
a->rexpr = (Node *) e;
expr = a;
}
else
expr = e;
}
/* otherwise, we have an expression from an ON clause... */
else
{
if (expr != NULL)
{
A_Expr *a = makeNode(A_Expr);
a->oper = AND;
a->opname = NULL;
a->lexpr = (Node *) expr;
a->rexpr = (Node *) qual;
expr = a;
}
else
expr = (A_Expr *) qual;
}
}
return ((Node *) transformExpr(pstate, (Node *) expr, EXPR_COLUMN_FIRST));
}
#endif
static char *
transformTableEntry(ParseState *pstate, RangeVar *r)
{
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, TRUE);
return refname;
}
/*
* 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 now as an extension.)
*
* The FROM clause can now contain JoinExpr nodes, which contain parsing info
* for inner and outer joins. The USING clause must be expanded into a qualification
* for an inner join at least, since that is compatible with the old syntax.
* Not sure yet how to handle outer joins, but it will become clear eventually?
* - thomas 1998-12-16
*/
static void
parseFromClause(ParseState *pstate, List *frmList, Node **qual)
{
List *fl;
if (qual != NULL)
*qual = NULL;
foreach(fl, frmList)
{
Node *n = lfirst(fl);
/*
* 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.
*/
if (IsA(n, RangeVar))
transformTableEntry(pstate, (RangeVar *) n);
else if (IsA(n, JoinExpr))
{
JoinExpr *j = (JoinExpr *) n;
#ifdef ENABLE_OUTER_JOINS
char *lname = transformTableEntry(pstate, (RangeVar *) j->larg);
#endif
char *rname;
if (IsA((Node *) j->rarg, RangeVar))
rname = transformTableEntry(pstate, (RangeVar *) j->rarg);
else
elog(ERROR, "Nested JOINs are not yet supported");
#ifdef ENABLE_OUTER_JOINS
if (j->jointype == INNER_P)
{
/*
* This is an inner join, so rip apart the join node and
* transform into a traditional FROM list. NATURAL JOIN
* and USING clauses both change the shape of the result.
* Need to generate a list of result columns to use for
* target list expansion and validation. Not doing this
* yet though!
*/
if (IsA(j->quals, List))
j->quals = lcons(transformUsingClause(pstate, (List *) j->quals, lname, rname), NIL);
if (qual == NULL)
elog(ERROR, "JOIN/ON not supported in this context");
if (*qual == NULL)
*qual = lfirst(j->quals);
else
elog(ERROR, "Multiple JOIN/ON clauses not handled (internal error)");
/*
* if we are transforming this node back into a FROM list,
* then we will need to replace the node with two nodes.
* Will need access to the previous list item to change
* the link pointer to reference these new nodes. Try
* accumulating and returning a new list. - thomas
* 1999-01-08 Not doing this yet though!
*/
}
else if ((j->jointype == LEFT)
|| (j->jointype == RIGHT)
|| (j->jointype == FULL))
elog(ERROR, "OUTER JOIN is not implemented");
else
elog(ERROR, "Unrecognized JOIN clause; tag is %d (internal error)",
j->jointype);
#else
elog(ERROR, "JOIN expressions are not yet implemented");
#endif
}
else
elog(ERROR, "parseFromClause: unexpected FROM clause node (internal error)"
"\n\t%s", nodeToString(n));
}
}
/*
* findTargetlistEntry -
* Returns the targetlist entry matching the given (untransformed) node.
* If no matching entry exists, one is created and appended to the target
* list as a "resjunk" node.
*
* node the ORDER BY or GROUP BY expression to be matched
* tlist the existing target list (NB: this cannot be NIL, which is a
* good thing since we'd be unable to append to it...)
* clause identifies clause type for error messages.
*/
static TargetEntry *
findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause,
char *uniqueFlag)
{
TargetEntry *target_result = NULL;
List *tl;
Node *expr;
/*----------
* Handle two special cases as mandated by the SQL92 spec:
*
* 1. ORDER/GROUP BY ColumnName
* For a bare identifier, we search for a matching column name
* in the existing target list. Multiple matches are an error
* unless they refer to identical values; for example,
* we allow SELECT a, a FROM table ORDER BY a
* but not SELECT a AS b, b FROM table ORDER BY b
* If no match is found, we fall through and treat the identifier
* as an expression.
*
* 2. ORDER/GROUP BY IntegerConstant
* This means to use the n'th item in the existing target list.
* Note that it would make no sense to order/group by an actual
* constant, so this does not create a conflict with our extension
* to order/group by an expression.
*
* Note that pre-existing resjunk targets must not be used in either case.
*----------
*/
if (IsA(node, Ident) && ((Ident *) node)->indirection == NIL)
{
char *name = ((Ident *) node)->name;
foreach(tl, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(tl);
Resdom *resnode = tle->resdom;
if (!resnode->resjunk &&
strcmp(resnode->resname, name) == 0)
{
if (target_result != NULL)
{
if (! equal(target_result->expr, tle->expr))
elog(ERROR, "%s BY '%s' is ambiguous",
clauseText[clause], name);
}
else
target_result = tle;
/* Stay in loop to check for ambiguity */
}
}
if (target_result != NULL)
return target_result; /* return the first match */
}
if (IsA(node, A_Const))
{
Value *val = &((A_Const *) node)->val;
int targetlist_pos = 0;
int target_pos;
if (nodeTag(val) != T_Integer)
elog(ERROR, "Non-integer constant in %s BY", clauseText[clause]);
target_pos = intVal(val);
foreach(tl, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(tl);
Resdom *resnode = tle->resdom;
if (!resnode->resjunk)
{
if (++targetlist_pos == target_pos)
return tle; /* return the unique match */
}
}
elog(ERROR, "%s BY position %d is not in target list",
clauseText[clause], target_pos);
}
/*
* Otherwise, we have an expression (this is a Postgres extension
* not found in SQL92). Convert the untransformed node to a
* transformed expression, and search for a match in the tlist.
* NOTE: it doesn't really matter whether there is more than one
* match. Also, we are willing to match a resjunk target here,
* though the above cases must ignore resjunk targets.
*/
expr = transformExpr(pstate, node, EXPR_COLUMN_FIRST);
foreach(tl, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(tl);
if (equal(expr, tle->expr))
return tle;
}
/*
* If no matches, construct a new target entry which is appended to
* the end of the target list. This target is set to be resjunk =
* TRUE so that it will not be projected into the final tuple.
*/
if(clause == ORDER_CLAUSE && uniqueFlag) {
elog(ERROR, "ORDER BY columns must appear in SELECT DISTINCT target list");
}
target_result = transformTargetEntry(pstate, node, expr, NULL, true);
lappend(tlist, target_result);
return target_result;
}
/*
* transformGroupClause -
* transform a Group By clause
*
*/
List *
transformGroupClause(ParseState *pstate, List *grouplist, List *targetlist)
{
List *glist = NIL,
*gl;
foreach(gl, grouplist)
{
TargetEntry *tle;
tle = findTargetlistEntry(pstate, lfirst(gl),
targetlist, GROUP_CLAUSE, NULL);
/* avoid making duplicate grouplist entries */
if (! exprIsInSortList(tle->expr, glist, targetlist))
{
GroupClause *grpcl = makeNode(GroupClause);
grpcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
grpcl->sortop = oprid(oper("<",
tle->resdom->restype,
tle->resdom->restype, false));
glist = lappend(glist, grpcl);
}
}
return glist;
}
/*
* transformSortClause -
* transform an Order By clause
*
*/
List *
transformSortClause(ParseState *pstate,
List *orderlist,
List *targetlist,
char *uniqueFlag)
{
List *sortlist = NIL;
List *olitem;
/* Transform all the explicit ORDER BY clauses */
foreach(olitem, orderlist)
{
SortGroupBy *sortby = lfirst(olitem);
TargetEntry *tle;
tle = findTargetlistEntry(pstate, sortby->node,
targetlist, ORDER_CLAUSE, uniqueFlag);
sortlist = addTargetToSortList(tle, sortlist, targetlist,
sortby->useOp);
}
/* If we have a DISTINCT clause, add any necessary entries to
* the sortlist to ensure that all the DISTINCT columns will be
* sorted. A subsequent UNIQUE pass will then do the right thing.
*/
if (uniqueFlag)
{
if (uniqueFlag[0] == '*')
{
/*
* concatenate all elements from target list that are not
* already in the sortby list
*/
sortlist = addAllTargetsToSortList(sortlist, targetlist);
}
else
{
TargetEntry *tle = NULL;
char *uniqueAttrName = uniqueFlag;
List *i;
/* only create sort clause with the specified unique attribute */
foreach(i, targetlist)
{
tle = (TargetEntry *) lfirst(i);
if (strcmp(tle->resdom->resname, uniqueAttrName) == 0)
break;
}
if (i == NIL)
elog(ERROR, "All fields in the UNIQUE ON clause must appear in the target list");
sortlist = addTargetToSortList(tle, sortlist, targetlist, NULL);
}
}
return sortlist;
}
/*
* addAllTargetsToSortList
* Make sure all targets in the targetlist are in the ORDER BY list,
* adding the not-yet-sorted ones to the end of the list.
* This is typically used to help implement SELECT DISTINCT.
*
* Returns the updated ORDER BY list.
*/
List *
addAllTargetsToSortList(List *sortlist, List *targetlist)
{
List *i;
foreach(i, targetlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(i);
sortlist = addTargetToSortList(tle, sortlist, targetlist, NULL);
}
return sortlist;
}
/*
* addTargetToSortList
* If the given targetlist entry isn't already in the ORDER BY list,
* add it to the end of the list, using the sortop with given name
* or any available sort operator if opname == NULL.
*
* Returns the updated ORDER BY list.
*/
static List *
addTargetToSortList(TargetEntry *tle, List *sortlist, List *targetlist,
char *opname)
{
/* avoid making duplicate sortlist entries */
if (! exprIsInSortList(tle->expr, sortlist, targetlist))
{
SortClause *sortcl = makeNode(SortClause);
sortcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
if (opname)
sortcl->sortop = oprid(oper(opname,
tle->resdom->restype,
tle->resdom->restype, false));
else
sortcl->sortop = any_ordering_op(tle->resdom->restype);
sortlist = lappend(sortlist, sortcl);
}
return sortlist;
}
/*
* assignSortGroupRef
* Assign the targetentry an unused ressortgroupref, if it doesn't
* already have one. Return the assigned or pre-existing refnumber.
*
* 'tlist' is the targetlist containing (or to contain) the given targetentry.
*/
Index
assignSortGroupRef(TargetEntry *tle, List *tlist)
{
Index maxRef;
List *l;
if (tle->resdom->ressortgroupref) /* already has one? */
return tle->resdom->ressortgroupref;
/* easiest way to pick an unused refnumber: max used + 1 */
maxRef = 0;
foreach(l, tlist)
{
Index ref = ((TargetEntry *) lfirst(l))->resdom->ressortgroupref;
if (ref > maxRef)
maxRef = ref;
}
tle->resdom->ressortgroupref = maxRef + 1;
return tle->resdom->ressortgroupref;
}
/*
* exprIsInSortList
* Is the given expression already in the sortlist?
* Note we will say 'yes' if it is equal() to any sortlist item,
* even though that might be a different targetlist member.
*
* Works for both SortClause and GroupClause lists.
*/
static bool
exprIsInSortList(Node *expr, List *sortList, List *targetList)
{
List *i;
foreach(i, sortList)
{
SortClause *scl = (SortClause *) lfirst(i);
if (equal(expr, get_sortgroupclause_expr(scl, targetList)))
return true;
}
return false;
}
/* transformUnionClause()
* Transform a UNION clause.
* Note that the union clause is actually a fully-formed select structure.
* So, it is evaluated as a select, then the resulting target fields
* are matched up to ensure correct types in the results.
* The select clause parsing is done recursively, so the unions are evaluated
* right-to-left. One might want to look at all columns from all clauses before
* trying to coerce, but unless we keep track of the call depth we won't know
* when to do this because of the recursion.
* Let's just try matching in pairs for now (right to left) and see if it works.
* - thomas 1998-05-22
*/
#ifdef NOT_USED
static List *
transformUnionClause(List *unionClause, List *targetlist)
{
List *union_list = NIL;
List *qlist,
*qlist_item;
if (unionClause)
{
/* recursion */
qlist = parse_analyze(unionClause, NULL);
foreach(qlist_item, qlist)
{
Query *query = (Query *) lfirst(qlist_item);
List *prev_target = targetlist;
List *next_target;
int prev_len = 0,
next_len = 0;
foreach(prev_target, targetlist)
if (!((TargetEntry *) lfirst(prev_target))->resdom->resjunk)
prev_len++;
foreach(next_target, query->targetList)
if (!((TargetEntry *) lfirst(next_target))->resdom->resjunk)
next_len++;
if (prev_len != next_len)
elog(ERROR, "Each UNION clause must have the same number of columns");
foreach(next_target, query->targetList)
{
Oid itype;
Oid otype;
otype = ((TargetEntry *) lfirst(prev_target))->resdom->restype;
itype = ((TargetEntry *) lfirst(next_target))->resdom->restype;
/* one or both is a NULL column? then don't convert... */
if (otype == InvalidOid)
{
/* propagate a known type forward, if available */
if (itype != InvalidOid)
((TargetEntry *) lfirst(prev_target))->resdom->restype = itype;
#if FALSE
else
{
((TargetEntry *) lfirst(prev_target))->resdom->restype = UNKNOWNOID;
((TargetEntry *) lfirst(next_target))->resdom->restype = UNKNOWNOID;
}
#endif
}
else if (itype == InvalidOid)
{
}
/* they don't match in type? then convert... */
else if (itype != otype)
{
Node *expr;
expr = ((TargetEntry *) lfirst(next_target))->expr;
expr = CoerceTargetExpr(NULL, expr, itype, otype, -1);
if (expr == NULL)
{
elog(ERROR, "Unable to transform %s to %s"
"\n\tEach UNION clause must have compatible target types",
typeidTypeName(itype),
typeidTypeName(otype));
}
((TargetEntry *) lfirst(next_target))->expr = expr;
((TargetEntry *) lfirst(next_target))->resdom->restype = otype;
}
/* both are UNKNOWN? then evaluate as text... */
else if (itype == UNKNOWNOID)
{
((TargetEntry *) lfirst(next_target))->resdom->restype = TEXTOID;
((TargetEntry *) lfirst(prev_target))->resdom->restype = TEXTOID;
}
prev_target = lnext(prev_target);
}
union_list = lappend(union_list, query);
}
return union_list;
}
else
return NIL;
}
#endif