postgresql/src/backend/parser/parse_clause.c

/*-------------------------------------------------------------------------
 *
 * 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 1.33 1999/05/17 17:03:32 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"
#include "parser/parse_coerce.h"
#include "nodes/print.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);

Attr *makeAttr(char *relname, char *attname);

#ifdef ENABLE_OUTER_JOINS
Node *transformUsingClause(ParseState *pstate, List *onList, char *lname, char *rname);
#endif

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;
}

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;
}

#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);

#ifdef PARSEDEBUG
printf("transformUsingClause- transform %s", nodeToString(i));
#endif

			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;
			}

#ifdef PARSEDEBUG
printf("transformUsingClause- transform %s", nodeToString(qual));
#endif

		}

#ifdef PARSEDEBUG
printf(" to %s\n", nodeToString(expr));
#endif
	}
	return ((Node *)transformExpr(pstate, (Node *)expr, EXPR_COLUMN_FIRST));
}
#endif

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
 */
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;

			if (length(targetlist) != length(query->targetList))
				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;
}	/* transformUnionClause() */