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parse_clause.c
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Bruce Momjian authoredBruce Momjian authored
parse_clause.c 20.11 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 1.39 1999/07/15 22:39:34 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "postgres.h"
#include "access/heapam.h"
#include "parser/parse_clause.h"
#include "parser/parse_expr.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "parser/parse_coerce.h"
#include "nodes/relation.h"
#include "parse.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);
static void parseFromClause(ParseState *pstate, List *frmList, Node **qual);
#ifdef ENABLE_OUTER_JOINS
Node *transformUsingClause(ParseState *pstate, List *onList, char *lname, char *rname);
#endif
static char *transformTableEntry(ParseState *pstate, RangeVar *r);
/*
* makeRangeTable -
* make a range table with the specified relation (optional) and the
* from_clause.
*/
void
makeRangeTable(ParseState *pstate, char *relname, List *frmList, Node **qual)
{
RangeTblEntry *rte;
int sublevels_up;
parseFromClause(pstate, frmList, qual);
if (relname == NULL)
return;
if ((refnameRangeTablePosn(pstate, relname, &sublevels_up) == 0)
|| (sublevels_up != 0))
rte = addRangeTableEntry(pstate, relname, relname, 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);
pstate->p_target_rangetblentry = rte;
pstate->p_target_relation = heap_open(rte->relid);
/* will close relation later */
}
/*
* 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 NOT_USED
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. */
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);
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);
Assert(qual != NULL);
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 Resdom in the target list matching the specified varname
* and range. If none exist one is created.
*
* Rewritten for ver 6.4 to handle expressions in the GROUP/ORDER BY clauses.
* - daveh@insightdist.com 1998-07-31
*
*/
static TargetEntry *
findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause)
{
List *l;
int rtable_pos = 0,
target_pos = 0,
targetlist_pos = 0; TargetEntry *target_result = NULL;
Value *val = NULL;
char *relname = NULL;
char *name = NULL;
Node *expr = NULL;
int relCnt = 0;
/* Pull out some values before looping thru target list */
switch (nodeTag(node))
{
case T_Attr:
relname = ((Attr *) node)->relname;
val = (Value *) lfirst(((Attr *) node)->attrs);
name = strVal(val);
rtable_pos = refnameRangeTablePosn(pstate, relname, NULL);
relCnt = length(pstate->p_rtable);
break;
case T_Ident:
name = ((Ident *) node)->name;
relCnt = length(pstate->p_rtable);
break;
case T_A_Const:
val = &((A_Const *) node)->val;
if (nodeTag(val) != T_Integer)
elog(ERROR, "Illegal Constant in %s BY", clauseText[clause]);
target_pos = intVal(val);
break;
case T_FuncCall:
case T_A_Expr:
expr = transformExpr(pstate, node, EXPR_COLUMN_FIRST);
break;
default:
elog(ERROR, "Illegal %s BY node = %d", clauseText[clause], nodeTag(node));
}
/*
* Loop through target entries and try to match to node
*/
foreach(l, tlist)
{
TargetEntry *target = (TargetEntry *) lfirst(l);
Resdom *resnode = target->resdom;
Var *var = (Var *) target->expr;
char *resname = resnode->resname;
int test_rtable_pos = var->varno;
++targetlist_pos;
switch (nodeTag(node))
{
case T_Attr:
if (strcmp(resname, name) == 0 && rtable_pos == test_rtable_pos)
{
/*
* Check for only 1 table & ORDER BY -ambiguity does
* not matter here
*/
if (clause == ORDER_CLAUSE && relCnt == 1)
return target;
if (target_result != NULL)
elog(ERROR, "%s BY '%s' is ambiguous", clauseText[clause], name);
else
target_result = target; /* Stay in loop to check for ambiguity */
}
break;
case T_Ident:
if (strcmp(resname, name) == 0)
{
/*
* Check for only 1 table & ORDER BY -ambiguity does
* not matter here
*/
if (clause == ORDER_CLAUSE && relCnt == 1)
return target;
if (target_result != NULL)
elog(ERROR, "%s BY '%s' is ambiguous", clauseText[clause], name);
else
target_result = target;
/* Stay in loop to check for ambiguity */
}
break;
case T_A_Const:
if (target_pos == targetlist_pos)
{
/* Can't be ambigious and we got what we came for */
return target;
}
break;
case T_FuncCall:
case T_A_Expr:
if (equal(expr, target->expr))
{
/*
* Check for only 1 table & ORDER BY -ambiguity does
* not matter here
*/
if (clause == ORDER_CLAUSE)
return target;
if (target_result != NULL)
elog(ERROR, "GROUP BY has ambiguous expression");
else
target_result = target;
}
break;
default:
elog(ERROR, "Illegal %s BY node = %d", clauseText[clause], nodeTag(node));
}
}
/*
* 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 (target_result == NULL)
{
switch (nodeTag(node))
{
case T_Attr:
target_result = MakeTargetEntryIdent(pstate, node,
&((Attr *) node)->relname, NULL,
((Attr *) node)->relname, true);
lappend(tlist, target_result);
break;
case T_Ident:
target_result = MakeTargetEntryIdent(pstate, node,
&((Ident *) node)->name, NULL,
((Ident *) node)->name, true);
lappend(tlist, target_result);
break;
case T_A_Const:
/*
* If we got this far, then must have been an out-of-range
* column number
*/
elog(ERROR, "%s BY position %d is not in target list", clauseText[clause], target_pos);
break;
case T_FuncCall:
case T_A_Expr:
target_result = MakeTargetEntryExpr(pstate, "resjunk", expr, false, true);
lappend(tlist, target_result);
break;
default:
elog(ERROR, "Illegal %s BY node = %d", clauseText[clause], nodeTag(node));
break;
}
}
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 = findTargetlistEntry(pstate, lfirst(grouplist), targetlist, GROUP_CLAUSE);
resdom = restarget->resdom;
grpcl->grpOpoid = oprid(oper("<",
resdom->restype,
resdom->restype, false));
if (glist == NIL)
{
int groupref = length(glist) + 1;
restarget->resdom->resgroupref = groupref;
grpcl->tleGroupref = groupref;
gl = glist = lcons(grpcl, NIL);
}
else
{
List *i;
foreach(i, glist)
{
GroupClause *gcl = (GroupClause *) lfirst(i);
if (equal(get_groupclause_expr(gcl, targetlist),
restarget->expr))
break;
}
if (i == NIL) /* not in grouplist already */
{
int groupref = length(glist) + 1;
restarget->resdom->resgroupref = groupref;
grpcl->tleGroupref = groupref;
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;
restarget = findTargetlistEntry(pstate, sortby->node, targetlist, ORDER_CLAUSE);
sortcl->resdom = resdom = restarget->resdom;
/*
* if we have InvalidOid, then this is a NULL field and don't need
* to sort
*/
if (resdom->restype == InvalidOid)
resdom->restype = INT4OID;
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);
/*
* We use equal() here because we are called for UNION
* from the optimizer, and at that point, the sort
* clause resdom pointers don't match the target list
* resdom pointers
*/
if (equal(sortcl->resdom, tlelt->resdom))
break;
s = lnext(s);
}
if (s == NIL)
{
/* not a member of the sortclauses yet */
SortClause *sortcl = makeNode(SortClause);
if (tlelt->resdom->restype == InvalidOid)
tlelt->resdom->restype = INT4OID;
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(ERROR, "All fields in the UNIQUE ON clause must appear in the target list");
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.
* 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);
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