postgresql/src/backend/parser/parse_target.c

/*-------------------------------------------------------------------------
 *
 * parse_target.c
 *	  handle target lists
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/parser/parse_target.c,v 1.118 2004/05/26 04:41:30 neilc Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "commands/dbcommands.h"
#include "miscadmin.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"


static void markTargetListOrigin(ParseState *pstate, Resdom *res, Var *var);
static List *ExpandAllTables(ParseState *pstate);
static char *FigureColname(Node *node);
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)
{
	Oid			type_id;
	int32		type_mod;
	Resdom	   *resnode;

	/* Transform the node if caller didn't do it already */
	if (expr == NULL)
		expr = transformExpr(pstate, node);

	type_id = exprType(expr);
	type_mod = exprTypmod(expr);

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

	resnode = makeResdom((AttrNumber) pstate->p_next_resno++,
						 type_id,
						 type_mod,
						 colname,
						 resjunk);

	return makeTargetEntry(resnode, (Expr *) expr);
}


/*
 * 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.
 */
List *
transformTargetList(ParseState *pstate, List *targetlist)
{
	FastList	p_target;
	ListCell   *o_target;

	FastListInit(&p_target);

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

		if (IsA(res->val, ColumnRef))
		{
			ColumnRef  *cref = (ColumnRef *) res->val;
			List	   *fields = cref->fields;

			if (strcmp(strVal(llast(fields)), "*") == 0)
			{
				int		numnames = length(fields);

				if (numnames == 1)
				{
					/*
					 * Target item is a single '*', expand all tables
					 * (e.g., SELECT * FROM emp)
					 */
					FastConc(&p_target,
							 ExpandAllTables(pstate));
				}
				else
				{
					/*
					 * Target item is relation.*, expand that table
					 * (e.g., SELECT emp.*, dname FROM emp, dept)
					 */
					char	   *schemaname;
					char	   *relname;
					RangeTblEntry *rte;
					int			sublevels_up;

					switch (numnames)
					{
						case 2:
							schemaname = NULL;
							relname = strVal(linitial(fields));
							break;
						case 3:
							schemaname = strVal(linitial(fields));
							relname = strVal(lsecond(fields));
							break;
						case 4:
						{
							char	   *name1 = strVal(linitial(fields));

							/*
							 * We check the catalog name and then ignore
							 * it.
							 */
							if (strcmp(name1, get_database_name(MyDatabaseId)) != 0)
								ereport(ERROR,
										(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
										 errmsg("cross-database references are not implemented: %s",
												NameListToString(fields))));
							schemaname = strVal(lsecond(fields));
							relname = strVal(lthird(fields));
							break;
						}
						default:
							ereport(ERROR,
									(errcode(ERRCODE_SYNTAX_ERROR),
									 errmsg("improper qualified name (too many dotted names): %s",
											NameListToString(fields))));
							schemaname = NULL;		/* keep compiler quiet */
							relname = NULL;
							break;
					}

					rte = refnameRangeTblEntry(pstate, schemaname, relname,
											   &sublevels_up);
					if (rte == NULL)
						rte = addImplicitRTE(pstate, makeRangeVar(schemaname,
																  relname));

					FastConc(&p_target,
							 expandRelAttrs(pstate, rte));
				}
			}
			else
			{
				/* Plain ColumnRef node, treat it as an expression */
				FastAppend(&p_target,
						   transformTargetEntry(pstate,
												res->val,
												NULL,
												res->name,
												false));
			}
		}
		else
		{
			/* Everything else but ColumnRef */
			FastAppend(&p_target,
					   transformTargetEntry(pstate,
											res->val,
											NULL,
											res->name,
											false));
		}
	}

	return FastListValue(&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->resdom, (Var *) tle->expr);
	}
}

/*
 * markTargetListOrigin()
 *		If 'var' is a Var of a plain relation, mark 'res' with its origin
 *
 * 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, Resdom *res, Var *var)
{
	RangeTblEntry *rte;
	AttrNumber	attnum;

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

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

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

				Assert(attnum > 0 && attnum <= length(rte->joinaliasvars));
				aliasvar = (Var *) nth(attnum - 1, rte->joinaliasvars);
				markTargetListOrigin(pstate, res, aliasvar);
			}
			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 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 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;
	Resdom	   *resnode = tle->resdom;
	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
	 * an array element with DEFAULT, since there can't be any default for
	 * individual elements of a column.
	 */
	if (tle->expr && IsA(tle->expr, SetToDefault))
	{
		SetToDefault *def = (SetToDefault *) tle->expr;

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

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

	/*
	 * If there are subscripts on the target column, prepare an array
	 * assignment expression.  This will generate an array value that the
	 * source value has been inserted into, which can then be placed in
	 * the new tuple constructed by INSERT or UPDATE. Note that
	 * transformArraySubscripts takes care of type coercion.
	 */
	if (indirection)
	{
		Node	   *arrayBase;
		ArrayRef   *aref;

		if (pstate->p_is_insert)
		{
			/*
			 * The command is INSERT INTO table (arraycol[subscripts]) ...
			 * so there is not really a source array value to work with.
			 * Let the executor do something reasonable, if it can. Notice
			 * that we force transformArraySubscripts to treat the
			 * subscripting op as an array-slice op below, so the source
			 * data will have been coerced to the array type.
			 */
			arrayBase = NULL;	/* signal there is no source array */
		}
		else
		{
			/*
			 * Build a Var for the array to be updated.
			 */
			arrayBase = (Node *) make_var(pstate,
										  pstate->p_target_rangetblentry,
										  attrno);
		}

		aref = transformArraySubscripts(pstate,
										arrayBase,
										attrtype,
										attrtypmod,
										indirection,
										pstate->p_is_insert,
										(Node *) tle->expr);
		tle->expr = (Expr *) aref;
	}
	else
	{
		/*
		 * For normal non-subscripted target column, do type checking and
		 * coercion.  But accept InvalidOid, which indicates the source is
		 * a NULL constant.  (XXX is that still true?)
		 */
		if (type_id != InvalidOid)
		{
			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.")));
		}
	}

	/*
	 * The result of the target expression should now match the
	 * destination column's type.
	 */
	resnode->restype = attrtype;
	resnode->restypmod = attrtypmod;
	/*
	 * 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.)
	 */
	resnode->resno = (AttrNumber) attrno;
	resnode->resname = colname;
}


/*
 * checkInsertTargets -
 *	  generate a list of INSERT column targets if not supplied, or
 *	  test supplied column names to make sure they are in target table.
 *	  Also return an integer list of the columns' attribute numbers.
 */
List *
checkInsertTargets(ParseState *pstate, List *cols, List **attrnos)
{
	*attrnos = NIL;

	if (cols == NIL)
	{
		/*
		 * Generate default column list for INSERT.
		 */
		Form_pg_attribute *attr = pstate->p_target_relation->rd_att->attrs;
		int			numcol = pstate->p_target_relation->rd_rel->relnatts;
		int			i;

		for (i = 0; i < numcol; i++)
		{
			ResTarget  *col;

			if (attr[i]->attisdropped)
				continue;

			col = makeNode(ResTarget);
			col->name = pstrdup(NameStr(attr[i]->attname));
			col->indirection = NIL;
			col->val = NULL;
			cols = lappend(cols, col);
			*attrnos = lappendi(*attrnos, i + 1);
		}
	}
	else
	{
		/*
		 * Do initial validation of user-supplied INSERT column list.
		 */
		ListCell   *tl;

		foreach(tl, cols)
		{
			char	   *name = ((ResTarget *) lfirst(tl))->name;
			int			attrno;

			/* Lookup column name, ereport on failure */
			attrno = attnameAttNum(pstate->p_target_relation, name, false);
			/* Check for duplicates */
			if (intMember(attrno, *attrnos))
				ereport(ERROR,
						(errcode(ERRCODE_DUPLICATE_COLUMN),
					  errmsg("column \"%s\" specified more than once",
							 name)));
			*attrnos = lappendi(*attrnos, attrno);
		}
	}

	return cols;
}

/* ExpandAllTables()
 * Turns '*' (in the target list) into a list of targetlist entries.
 *
 * tlist entries are generated for each relation appearing at the top level
 * of the query's namespace, except for RTEs marked not inFromCl.  (These
 * may include NEW/OLD pseudo-entries, implicit RTEs, etc.)
 */
static List *
ExpandAllTables(ParseState *pstate)
{
	List	   *target = NIL;
	bool		found_table = false;
	ListCell   *ns;

	foreach(ns, pstate->p_namespace)
	{
		Node	   *n = (Node *) lfirst(ns);
		RangeTblEntry *rte;

		if (IsA(n, RangeTblRef))
			rte = rt_fetch(((RangeTblRef *) n)->rtindex,
						   pstate->p_rtable);
		else if (IsA(n, JoinExpr))
			rte = rt_fetch(((JoinExpr *) n)->rtindex,
						   pstate->p_rtable);
		else
		{
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
			rte = NULL;			/* keep compiler quiet */
		}

		/*
		 * Ignore added-on relations that were not listed in the FROM
		 * clause.
		 */
		if (!rte->inFromCl)
			continue;

		found_table = true;
		target = nconc(target, expandRelAttrs(pstate, rte));
	}

	/* Check for SELECT *; */
	if (!found_table)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
			  errmsg("SELECT * with no tables specified is not valid")));

	return target;
}

/*
 * FigureColname -
 *	  if the name of the resulting column is not specified in the target
 *	  list, we have to guess a suitable name.  The SQL spec provides some
 *	  guidance, but not much...
 *
 * Note that the argument is the *untransformed* parse tree for the target
 * item.  This is a shade easier to work with than the transformed tree.
 */
static char *
FigureColname(Node *node)
{
	char	   *name = NULL;

	FigureColnameInternal(node, &name);
	if (name != NULL)
		return name;
	/* default result if we can't guess anything */
	return "?column?";
}

static int
FigureColnameInternal(Node *node, char **name)
{
	int			strength = 0;

	if (node == NULL)
		return strength;

	switch (nodeTag(node))
	{
		case T_ColumnRef:
			{
				char	   *cname = strVal(llast(((ColumnRef *) node)->fields));

				if (strcmp(cname, "*") != 0)
				{
					*name = cname;
					return 2;
				}
			}
			break;
		case T_ExprFieldSelect:
			{
				ExprFieldSelect *efs = (ExprFieldSelect *) node;

				if (efs->fields)
				{
					char	   *fname = strVal(llast(efs->fields));

					if (strcmp(fname, "*") != 0)
					{
						*name = fname;
						return 2;
					}
				}
				return FigureColnameInternal(efs->arg, name);
			}
			break;
		case T_FuncCall:
			*name = strVal(llast(((FuncCall *) node)->funcname));
			return 2;
		case T_A_Expr:
			/* make nullif() act like a regular function */
			if (((A_Expr *) node)->kind == AEXPR_NULLIF)
			{
				*name = "nullif";
				return 2;
			}
			break;
		case T_A_Const:
			if (((A_Const *) node)->typename != NULL)
			{
				*name = strVal(llast(((A_Const *) node)->typename->names));
				return 1;
			}
			break;
		case T_TypeCast:
			strength = FigureColnameInternal(((TypeCast *) node)->arg,
											 name);
			if (strength <= 1)
			{
				if (((TypeCast *) node)->typename != NULL)
				{
					*name = strVal(llast(((TypeCast *) node)->typename->names));
					return 1;
				}
			}
			break;
		case T_CaseExpr:
			strength = FigureColnameInternal((Node *) ((CaseExpr *) node)->defresult,
											 name);
			if (strength <= 1)
			{
				*name = "case";
				return 1;
			}
			break;
		case T_ArrayExpr:
			/* make ARRAY[] act like a function */
			*name = "array";
			return 2;
		case T_RowExpr:
			/* make ROW() act like a function */
			*name = "row";
			return 2;
		case T_CoalesceExpr:
			/* make coalesce() act like a regular function */
			*name = "coalesce";
			return 2;
		default:
			break;
	}

	return strength;
}