parse_target.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * parse_target.c
 *	  handle target lists
 *
 * 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_target.c,v 1.138.2.2 2006/01/17 17:33:20 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "commands/dbcommands.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/bitmapset.h"
#include "nodes/makefuncs.h"
#include "parser/parsetree.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/typcache.h"


static void markTargetListOrigin(ParseState *pstate, TargetEntry *tle,
					 Var *var, int levelsup);
static Node *transformAssignmentIndirection(ParseState *pstate,
							   Node *basenode,
							   const char *targetName,
							   bool targetIsArray,
							   Oid targetTypeId,
							   int32 targetTypMod,
							   ListCell *indirection,
							   Node *rhs);
static List *ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref);
static List *ExpandAllTables(ParseState *pstate);
static List *ExpandIndirectionStar(ParseState *pstate, A_Indirection *ind);
static int	FigureColnameInternal(Node *node, char **name);


/*
 * transformTargetEntry()
 *	Transform any ordinary "expression-type" node into a targetlist entry.
 *	This is exported so that parse_clause.c can generate targetlist entries
 *	for ORDER/GROUP BY items that are not already in the targetlist.
 *
 * node		the (untransformed) parse tree for the value expression.
 * expr		the transformed expression, or NULL if caller didn't do it yet.
 * colname	the column name to be assigned, or NULL if none yet set.
 * resjunk	true if the target should be marked resjunk, ie, it is not
 *			wanted in the final projected tuple.
 */
TargetEntry *
transformTargetEntry(ParseState *pstate,
					 Node *node,
					 Node *expr,
					 char *colname,
					 bool resjunk)
{
	/* Transform the node if caller didn't do it already */
	if (expr == NULL)
		expr = transformExpr(pstate, node);

	if (colname == NULL && !resjunk)
	{
		/*
		 * Generate a suitable column name for a column without any explicit
		 * 'AS ColumnName' clause.
		 */
		colname = FigureColname(node);
	}

	return makeTargetEntry((Expr *) expr,
						   (AttrNumber) pstate->p_next_resno++,
						   colname,
						   resjunk);
}


/*
 * transformTargetList()
 * Turns a list of ResTarget's into a list of TargetEntry's.
 *
 * At this point, we don't care whether we are doing SELECT, INSERT,
 * or UPDATE; we just transform the given expressions (the "val" fields).
 */
List *
transformTargetList(ParseState *pstate, List *targetlist)
{
	List	   *p_target = NIL;
	ListCell   *o_target;

	foreach(o_target, targetlist)
	{
		ResTarget  *res = (ResTarget *) lfirst(o_target);

		/*
		 * Check for "something.*".  Depending on the complexity of the
		 * "something", the star could appear as the last name in ColumnRef,
		 * or as the last indirection item in A_Indirection.
		 */
		if (IsA(res->val, ColumnRef))
		{
			ColumnRef  *cref = (ColumnRef *) res->val;

			if (strcmp(strVal(llast(cref->fields)), "*") == 0)
			{
				/* It is something.*, expand into multiple items */
				p_target = list_concat(p_target,
									   ExpandColumnRefStar(pstate, cref));
				continue;
			}
		}
		else if (IsA(res->val, A_Indirection))
		{
			A_Indirection *ind = (A_Indirection *) res->val;
			Node	   *lastitem = llast(ind->indirection);

			if (IsA(lastitem, String) &&
				strcmp(strVal(lastitem), "*") == 0)
			{
				/* It is something.*, expand into multiple items */
				p_target = list_concat(p_target,
									   ExpandIndirectionStar(pstate, ind));
				continue;
			}
		}

		/*
		 * Not "something.*", so transform as a single expression
		 */
		p_target = lappend(p_target,
						   transformTargetEntry(pstate,
												res->val,
												NULL,
												res->name,
												false));
	}

	return p_target;
}


/*
 * markTargetListOrigins()
 *		Mark targetlist columns that are simple Vars with the source
 *		table's OID and column number.
 *
 * Currently, this is done only for SELECT targetlists, since we only
 * need the info if we are going to send it to the frontend.
 */
void
markTargetListOrigins(ParseState *pstate, List *targetlist)
{
	ListCell   *l;

	foreach(l, targetlist)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(l);

		markTargetListOrigin(pstate, tle, (Var *) tle->expr, 0);
	}
}

/*
 * markTargetListOrigin()
 *		If 'var' is a Var of a plain relation, mark 'tle' with its origin
 *
 * levelsup is an extra offset to interpret the Var's varlevelsup correctly.
 *
 * This is split out so it can recurse for join references.  Note that we
 * do not drill down into views, but report the view as the column owner.
 */
static void
markTargetListOrigin(ParseState *pstate, TargetEntry *tle,
					 Var *var, int levelsup)
{
	int			netlevelsup;
	RangeTblEntry *rte;
	AttrNumber	attnum;

	if (var == NULL || !IsA(var, Var))
		return;
	netlevelsup = var->varlevelsup + levelsup;
	rte = GetRTEByRangeTablePosn(pstate, var->varno, netlevelsup);
	attnum = var->varattno;

	switch (rte->rtekind)
	{
		case RTE_RELATION:
			/* It's a table or view, report it */
			tle->resorigtbl = rte->relid;
			tle->resorigcol = attnum;
			break;
		case RTE_SUBQUERY:
			/* Subselect-in-FROM: copy up from the subselect */
			if (attnum != InvalidAttrNumber)
			{
				TargetEntry *ste = get_tle_by_resno(rte->subquery->targetList,
													attnum);

				if (ste == NULL || ste->resjunk)
					elog(ERROR, "subquery %s does not have attribute %d",
						 rte->eref->aliasname, attnum);
				tle->resorigtbl = ste->resorigtbl;
				tle->resorigcol = ste->resorigcol;
			}
			break;
		case RTE_JOIN:
			/* Join RTE --- recursively inspect the alias variable */
			if (attnum != InvalidAttrNumber)
			{
				Var		   *aliasvar;

				Assert(attnum > 0 && attnum <= list_length(rte->joinaliasvars));
				aliasvar = (Var *) list_nth(rte->joinaliasvars, attnum - 1);
				markTargetListOrigin(pstate, tle, aliasvar, netlevelsup);
			}
			break;
		case RTE_SPECIAL:
		case RTE_FUNCTION:
			/* not a simple relation, leave it unmarked */
			break;
	}
}


/*
 * updateTargetListEntry()
 *	This is used in INSERT and UPDATE statements only.	It prepares a
 *	TargetEntry for assignment to a column of the target table.
 *	This includes coercing the given value to the target column's type
 *	(if necessary), and dealing with any subfield names or subscripts
 *	attached to the target column itself.
 *
 * pstate		parse state
 * tle			target list entry to be modified
 * colname		target column name (ie, name of attribute to be assigned to)
 * attrno		target attribute number
 * indirection	subscripts/field names for target column, if any
 */
void
updateTargetListEntry(ParseState *pstate,
					  TargetEntry *tle,
					  char *colname,
					  int attrno,
					  List *indirection)
{
	Oid			type_id;		/* type of value provided */
	Oid			attrtype;		/* type of target column */
	int32		attrtypmod;
	Relation	rd = pstate->p_target_relation;

	Assert(rd != NULL);
	if (attrno <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot assign to system column \"%s\"",
						colname)));
	attrtype = attnumTypeId(rd, attrno);
	attrtypmod = rd->rd_att->attrs[attrno - 1]->atttypmod;

	/*
	 * If the expression is a DEFAULT placeholder, insert the attribute's
	 * type/typmod into it so that exprType will report the right things. (We
	 * expect that the eventually substituted default expression will in fact
	 * have this type and typmod.)	Also, reject trying to update a subfield
	 * or array element with DEFAULT, since there can't be any default for
	 * portions of a column.
	 */
	if (tle->expr && IsA(tle->expr, SetToDefault))
	{
		SetToDefault *def = (SetToDefault *) tle->expr;

		def->typeId = attrtype;
		def->typeMod = attrtypmod;
		if (indirection)
		{
			if (IsA(linitial(indirection), A_Indices))
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot set an array element to DEFAULT")));
			else
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot set a subfield to DEFAULT")));
		}
	}

	/* Now we can use exprType() safely. */
	type_id = exprType((Node *) tle->expr);

	/*
	 * If there is indirection on the target column, prepare an array or
	 * subfield assignment expression.	This will generate a new column value
	 * that the source value has been inserted into, which can then be placed
	 * in the new tuple constructed by INSERT or UPDATE.
	 */
	if (indirection)
	{
		Node	   *colVar;

		if (pstate->p_is_insert)
		{
			/*
			 * The command is INSERT INTO table (col.something) ... so there
			 * is not really a source value to work with. Insert a NULL
			 * constant as the source value.
			 */
			colVar = (Node *) makeNullConst(attrtype);
		}
		else
		{
			/*
			 * Build a Var for the column to be updated.
			 */
			colVar = (Node *) make_var(pstate,
									   pstate->p_target_rangetblentry,
									   attrno);
		}

		tle->expr = (Expr *)
			transformAssignmentIndirection(pstate,
										   colVar,
										   colname,
										   false,
										   attrtype,
										   attrtypmod,
										   list_head(indirection),
										   (Node *) tle->expr);
	}
	else
	{
		/*
		 * For normal non-qualified target column, do type checking and
		 * coercion.
		 */
		tle->expr = (Expr *)
			coerce_to_target_type(pstate,
								  (Node *) tle->expr, type_id,
								  attrtype, attrtypmod,
								  COERCION_ASSIGNMENT,
								  COERCE_IMPLICIT_CAST);
		if (tle->expr == NULL)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("column \"%s\" is of type %s"
							" but expression is of type %s",
							colname,
							format_type_be(attrtype),
							format_type_be(type_id)),
			   errhint("You will need to rewrite or cast the expression.")));
	}

	/*
	 * Set the resno to identify the target column --- the rewriter and
	 * planner depend on this.	We also set the resname to identify the target
	 * column, but this is only for debugging purposes; it should not be
	 * relied on.  (In particular, it might be out of date in a stored rule.)
	 */
	tle->resno = (AttrNumber) attrno;
	tle->resname = colname;
}

/*
 * Process indirection (field selection or subscripting) of the target
 * column in INSERT/UPDATE.  This routine recurses for multiple levels
 * of indirection --- but note that several adjacent A_Indices nodes in
 * the indirection list are treated as a single multidimensional subscript
 * operation.
 *
 * In the initial call, basenode is a Var for the target column in UPDATE,
 * or a null Const of the target's type in INSERT.  In recursive calls,
 * basenode is NULL, indicating that a substitute node should be consed up if