parse_clause.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * parse_clause.c
 *	  handle clauses in parser
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/parser/parse_clause.c,v 1.143.2.1 2005/11/22 18:23:13 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/heapam.h"
#include "catalog/heap.h"
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
#include "parser/analyze.h"
#include "parser/parsetree.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"
#include "parser/parse_type.h"
#include "rewrite/rewriteManip.h"
#include "utils/builtins.h"
#include "utils/guc.h"


#define ORDER_CLAUSE 0
#define GROUP_CLAUSE 1
#define DISTINCT_ON_CLAUSE 2

static char *clauseText[] = {"ORDER BY", "GROUP BY", "DISTINCT ON"};

static void extractRemainingColumns(List *common_colnames,
						List *src_colnames, List *src_colvars,
						List **res_colnames, List **res_colvars);
static Node *transformJoinUsingClause(ParseState *pstate,
						 List *leftVars, List *rightVars);
static Node *transformJoinOnClause(ParseState *pstate, JoinExpr *j,
					  RangeTblEntry *l_rte,
					  RangeTblEntry *r_rte,
					  List *relnamespace,
					  Relids containedRels);
static RangeTblEntry *transformTableEntry(ParseState *pstate, RangeVar *r);
static RangeTblEntry *transformRangeSubselect(ParseState *pstate,
						RangeSubselect *r);
static RangeTblEntry *transformRangeFunction(ParseState *pstate,
					   RangeFunction *r);
static Node *transformFromClauseItem(ParseState *pstate, Node *n,
						RangeTblEntry **top_rte, int *top_rti,
						List **relnamespace,
						Relids *containedRels);
static Node *buildMergedJoinVar(ParseState *pstate, JoinType jointype,
				   Var *l_colvar, Var *r_colvar);
static TargetEntry *findTargetlistEntry(ParseState *pstate, Node *node,
					List **tlist, int clause);


/*
 * transformFromClause -
 *	  Process the FROM clause and add items to the query's range table,
 *	  joinlist, and namespaces.
 *
 * Note: we assume that pstate's p_rtable, p_joinlist, p_relnamespace, and
 * p_varnamespace lists were initialized to NIL when the pstate was created.
 * We will add onto any entries already present --- this is needed for rule
 * processing, as well as for UPDATE and DELETE.
 *
 * The range table may grow still further when we transform the expressions
 * in the query's quals and target list. (This is possible because in
 * POSTQUEL, we allowed references to relations not specified in the
 * from-clause.  PostgreSQL keeps this extension to standard SQL.)
 */
void
transformFromClause(ParseState *pstate, List *frmList)
{
	ListCell   *fl;

	/*
	 * The grammar will have produced a list of RangeVars, RangeSubselects,
	 * RangeFunctions, and/or JoinExprs. Transform each one (possibly adding
	 * entries to the rtable), check for duplicate refnames, and then add it
	 * to the joinlist and namespaces.
	 */
	foreach(fl, frmList)
	{
		Node	   *n = lfirst(fl);
		RangeTblEntry *rte;
		int			rtindex;
		List	   *relnamespace;
		Relids		containedRels;

		n = transformFromClauseItem(pstate, n,
									&rte,
									&rtindex,
									&relnamespace,
									&containedRels);
		checkNameSpaceConflicts(pstate, pstate->p_relnamespace, relnamespace);
		pstate->p_joinlist = lappend(pstate->p_joinlist, n);
		pstate->p_relnamespace = list_concat(pstate->p_relnamespace,
											 relnamespace);
		pstate->p_varnamespace = lappend(pstate->p_varnamespace, rte);
		bms_free(containedRels);
	}
}

/*
 * setTargetTable
 *	  Add the target relation of INSERT/UPDATE/DELETE to the range table,
 *	  and make the special links to it in the ParseState.
 *
 *	  We also open the target relation and acquire a write lock on it.
 *	  This must be done before processing the FROM list, in case the target
 *	  is also mentioned as a source relation --- we want to be sure to grab
 *	  the write lock before any read lock.
 *
 *	  If alsoSource is true, add the target to the query's joinlist and
 *	  namespace.  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.  (NOTE: we do not bother
 *	  to check for namespace conflict; we assume that the namespace was
 *	  initially empty in these cases.)
 *
 *	  Finally, we mark the relation as requiring the permissions specified
 *	  by requiredPerms.
 *
 *	  Returns the rangetable index of the target relation.
 */
int
setTargetTable(ParseState *pstate, RangeVar *relation,
			   bool inh, bool alsoSource, AclMode requiredPerms)
{
	RangeTblEntry *rte;
	int			rtindex;

	/* Close old target; this could only happen for multi-action rules */
	if (pstate->p_target_relation != NULL)
		heap_close(pstate->p_target_relation, NoLock);

	/*
	 * Open target rel and grab suitable lock (which we will hold till end of
	 * transaction).
	 *
	 * analyze.c will eventually do the corresponding heap_close(), but *not*
	 * release the lock.
	 */
	pstate->p_target_relation = heap_openrv(relation, RowExclusiveLock);

	/*
	 * Now build an RTE.
	 */
	rte = addRangeTableEntryForRelation(pstate, pstate->p_target_relation,
										NULL, inh, false);
	pstate->p_target_rangetblentry = rte;

	/* assume new rte is at end */
	rtindex = list_length(pstate->p_rtable);
	Assert(rte == rt_fetch(rtindex, pstate->p_rtable));

	/*
	 * Override addRangeTableEntry's default ACL_SELECT permissions check, and
	 * instead mark target table as requiring exactly the specified
	 * permissions.
	 *
	 * If we find an explicit reference to the rel later during parse
	 * analysis, scanRTEForColumn will add the ACL_SELECT bit back again. That
	 * can't happen for INSERT but it is possible for UPDATE and DELETE.
	 */
	rte->requiredPerms = requiredPerms;

	/*
	 * If UPDATE/DELETE, add table to joinlist and namespaces.
	 */
	if (alsoSource)
		addRTEtoQuery(pstate, rte, true, true, true);

	return rtindex;
}

/*
 * Simplify InhOption (yes/no/default) into boolean yes/no.
 *
 * The reason we do things this way is that we don't want to examine the
 * SQL_inheritance option flag until parse_analyze is run.	Otherwise,
 * we'd do the wrong thing with query strings that intermix SET commands
 * with queries.
 */
bool
interpretInhOption(InhOption inhOpt)
{
	switch (inhOpt)
	{
		case INH_NO:
			return false;
		case INH_YES:
			return true;
		case INH_DEFAULT:
			return SQL_inheritance;
	}
	elog(ERROR, "bogus InhOption value: %d", inhOpt);
	return false;				/* keep compiler quiet */
}

/*
 * Given an enum that indicates whether WITH / WITHOUT OIDS was
 * specified by the user, return true iff the specified table/result
 * set should be created with OIDs. This needs to be done after
 * parsing the query string because the return value can depend upon
 * the default_with_oids GUC var.
 */
bool
interpretOidsOption(ContainsOids opt)
{
	switch (opt)
	{
		case MUST_HAVE_OIDS:
			return true;

		case MUST_NOT_HAVE_OIDS:
			return false;

		case DEFAULT_OIDS:
			return default_with_oids;
	}

	elog(ERROR, "bogus ContainsOids value: %d", opt);
	return false;				/* keep compiler quiet */
}

/*
 * Extract all not-in-common columns from column lists of a source table
 */
static void
extractRemainingColumns(List *common_colnames,
						List *src_colnames, List *src_colvars,
						List **res_colnames, List **res_colvars)
{
	List	   *new_colnames = NIL;
	List	   *new_colvars = NIL;
	ListCell   *lnames,
			   *lvars;

	Assert(list_length(src_colnames) == list_length(src_colvars));

	forboth(lnames, src_colnames, lvars, src_colvars)
	{
		char	   *colname = strVal(lfirst(lnames));
		bool		match = false;
		ListCell   *cnames;

		foreach(cnames, common_colnames)
		{
			char	   *ccolname = strVal(lfirst(cnames));

			if (strcmp(colname, ccolname) == 0)
			{
				match = true;
				break;
			}
		}

		if (!match)
		{
			new_colnames = lappend(new_colnames, lfirst(lnames));
			new_colvars = lappend(new_colvars, lfirst(lvars));
		}
	}

	*res_colnames = new_colnames;
	*res_colvars = new_colvars;
}

/* transformJoinUsingClause()
 *	  Build a complete ON clause from a partially-transformed USING list.
 *	  We are given lists of nodes representing left and right match columns.
 *	  Result is a transformed qualification expression.
 */
static Node *
transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars)
{
	Node	   *result = NULL;
	ListCell   *lvars,
			   *rvars;

	/*
	 * We cheat a little bit here by building an untransformed operator tree
	 * whose leaves are the already-transformed Vars.  This is OK because
	 * transformExpr() won't complain about already-transformed subnodes.
	 */
	forboth(lvars, leftVars, rvars, rightVars)
	{
		Node	   *lvar = (Node *) lfirst(lvars);
		Node	   *rvar = (Node *) lfirst(rvars);
		A_Expr	   *e;

		e = makeSimpleA_Expr(AEXPR_OP, "=", copyObject(lvar), copyObject(rvar));

		if (result == NULL)
			result = (Node *) e;
		else
		{
			A_Expr	   *a;

			a = makeA_Expr(AEXPR_AND, NIL, result, (Node *) e);
			result = (Node *) a;
		}
	}

	/*
	 * Since the references are already Vars, and are certainly from the input
	 * relations, we don't have to go through the same pushups that
	 * transformJoinOnClause() does.  Just invoke transformExpr() to fix up
	 * the operators, and we're done.
	 */
	result = transformExpr(pstate, result);

	result = coerce_to_boolean(pstate, result, "JOIN/USING");

	return result;
}

/* transformJoinOnClause()
 *	  Transform the qual conditions for JOIN/ON.
 *	  Result is a transformed qualification expression.
 */
static Node *
transformJoinOnClause(ParseState *pstate, JoinExpr *j,
					  RangeTblEntry *l_rte,
					  RangeTblEntry *r_rte,
					  List *relnamespace,
					  Relids containedRels)
{
	Node	   *result;
	List	   *save_relnamespace;
	List	   *save_varnamespace;
	Relids		clause_varnos;
	int			varno;

	/*
	 * This is a tad tricky, for two reasons.  First, the namespace that the
	 * join expression should see is just the two subtrees of the JOIN plus
	 * any outer references from upper pstate levels.  So, temporarily set
	 * this pstate's namespace accordingly.  (We need not check for refname
	 * conflicts, because transformFromClauseItem() already did.) NOTE: this
	 * code is OK only because the ON clause can't legally alter the namespace
	 * by causing implicit relation refs to be added.
	 */
	save_relnamespace = pstate->p_relnamespace;
	save_varnamespace = pstate->p_varnamespace;

	pstate->p_relnamespace = relnamespace;
	pstate->p_varnamespace = list_make2(l_rte, r_rte);

	result = transformWhereClause(pstate, j->quals, "JOIN/ON");

	pstate->p_relnamespace = save_relnamespace;
	pstate->p_varnamespace = save_varnamespace;

	/*
	 * Second, we need to check that the ON condition doesn't refer to any
	 * rels outside the input subtrees of the JOIN.  It could do that despite
	 * our hack on the namespace if it uses fully-qualified names. So, grovel
	 * through the transformed clause and make sure there are no bogus
	 * references.	(Outer references are OK, and are ignored here.)
	 */
	clause_varnos = pull_varnos(result);
	clause_varnos = bms_del_members(clause_varnos, containedRels);
	if ((varno = bms_first_member(clause_varnos)) >= 0)
	{
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
		 errmsg("JOIN/ON clause refers to \"%s\", which is not part of JOIN",
				rt_fetch(varno, pstate->p_rtable)->eref->aliasname)));
	}
	bms_free(clause_varnos);

	return result;
}

/*
 * transformTableEntry --- transform a RangeVar (simple relation reference)
 */
static RangeTblEntry *
transformTableEntry(ParseState *pstate, RangeVar *r)
{
	RangeTblEntry *rte;

	/*
	 * mark 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.
	 */
	rte = addRangeTableEntry(pstate, r, r->alias,
							 interpretInhOption(r->inhOpt), true);

	return rte;
}


/*
 * transformRangeSubselect --- transform a sub-SELECT appearing in FROM
 */
static RangeTblEntry *
transformRangeSubselect(ParseState *pstate, RangeSubselect *r)
{
	List	   *parsetrees;
	Query	   *query;
	RangeTblEntry *rte;