tupdesc.c

PostgreSQL7.4.6 for Linux

TupleDescInitEntry(TupleDesc desc,
				   AttrNumber attributeNumber,
				   const char *attributeName,
				   Oid oidtypeid,
				   int32 typmod,
				   int attdim,
				   bool attisset)
{
	HeapTuple	tuple;
	Form_pg_type typeForm;
	Form_pg_attribute att;

	/*
	 * sanity checks
	 */
	AssertArg(PointerIsValid(desc));
	AssertArg(attributeNumber >= 1);
	AssertArg(attributeNumber <= desc->natts);
	AssertArg(!PointerIsValid(desc->attrs[attributeNumber - 1]));

	/*
	 * allocate storage for this attribute
	 */

	att = (Form_pg_attribute) palloc(ATTRIBUTE_TUPLE_SIZE);
	desc->attrs[attributeNumber - 1] = att;

	/*
	 * initialize the attribute fields
	 */
	att->attrelid = 0;			/* dummy value */

	/*
	 * Note: attributeName can be NULL, because the planner doesn't always
	 * fill in valid resname values in targetlists, particularly for resjunk
	 * attributes.
	 */
	if (attributeName != NULL)
		namestrcpy(&(att->attname), attributeName);
	else
		MemSet(NameStr(att->attname), 0, NAMEDATALEN);

	att->attstattarget = -1;
	att->attcacheoff = -1;
	att->atttypmod = typmod;

	att->attnum = attributeNumber;
	att->attndims = attdim;
	att->attisset = attisset;

	att->attnotnull = false;
	att->atthasdef = false;
	att->attisdropped = false;
	att->attislocal = true;
	att->attinhcount = 0;

	tuple = SearchSysCache(TYPEOID,
						   ObjectIdGetDatum(oidtypeid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for type %u", oidtypeid);

	/*
	 * type info exists so we initialize our attribute information from
	 * the type tuple we found..
	 */
	typeForm = (Form_pg_type) GETSTRUCT(tuple);

	att->atttypid = HeapTupleGetOid(tuple);

	/*
	 * There are a couple of cases where we must override the information
	 * stored in pg_type.
	 *
	 * First: if this attribute is a set, what is really stored in the
	 * attribute is the OID of a tuple in the pg_proc catalog. The pg_proc
	 * tuple contains the query string which defines this set - i.e., the
	 * query to run to get the set. So the atttypid (just assigned above)
	 * refers to the type returned by this query, but the actual length of
	 * this attribute is the length (size) of an OID.
	 *
	 * (Why not just make the atttypid point to the OID type, instead of the
	 * type the query returns?	Because the executor uses the atttypid to
	 * tell the front end what type will be returned, and in the end the
	 * type returned will be the result of the query, not an OID.)
	 *
	 * (Why not wait until the return type of the set is known (i.e., the
	 * recursive call to the executor to execute the set has returned)
	 * before telling the front end what the return type will be?  Because
	 * the executor is a delicate thing, and making sure that the correct
	 * order of front-end commands is maintained is messy, especially
	 * considering that target lists may change as inherited attributes
	 * are considered, etc.  Ugh.)
	 *
	 * Second: if we are dealing with a complex type (a tuple type), then
	 * pg_type will say that the representation is the same as Oid.  But
	 * if typmod is sizeof(Pointer) then the internal representation is
	 * actually a pointer to a TupleTableSlot, and we have to substitute
	 * that information.
	 *
	 * A set of complex type is first and foremost a set, so its
	 * representation is Oid not pointer.  So, test that case first.
	 */
	if (attisset)
	{
		att->attlen = sizeof(Oid);
		att->attbyval = true;
		att->attalign = 'i';
		att->attstorage = 'p';
	}
	else if (typeForm->typtype == 'c' && typmod == sizeof(Pointer))
	{
		att->attlen = sizeof(Pointer);
		att->attbyval = true;
		att->attalign = 'd';	/* kluge to work with 8-byte pointers */
		/* XXX ought to have a separate attalign value for pointers ... */
		att->attstorage = 'p';
	}
	else
	{
		att->attlen = typeForm->typlen;
		att->attbyval = typeForm->typbyval;
		att->attalign = typeForm->typalign;
		att->attstorage = typeForm->typstorage;
	}

	ReleaseSysCache(tuple);
}


/*
 * BuildDescForRelation
 *
 * Given a relation schema (list of ColumnDef nodes), build a TupleDesc.
 *
 * Note: the default assumption is no OIDs; caller may modify the returned
 * TupleDesc if it wants OIDs.
 */
TupleDesc
BuildDescForRelation(List *schema)
{
	int			natts;
	AttrNumber	attnum;
	List	   *p;
	TupleDesc	desc;
	AttrDefault *attrdef = NULL;
	TupleConstr *constr = (TupleConstr *) palloc(sizeof(TupleConstr));
	char	   *attname;
	int32		atttypmod;
	int			attdim;
	int			ndef = 0;
	bool		attisset;

	/*
	 * allocate a new tuple descriptor
	 */
	natts = length(schema);
	desc = CreateTemplateTupleDesc(natts, false);
	constr->has_not_null = false;

	attnum = 0;

	foreach(p, schema)
	{
		ColumnDef  *entry = lfirst(p);

		/*
		 * for each entry in the list, get the name and type information
		 * from the list and have TupleDescInitEntry fill in the attribute
		 * information we need.
		 */
		attnum++;

		attname = entry->colname;
		attisset = entry->typename->setof;
		atttypmod = entry->typename->typmod;
		attdim = length(entry->typename->arrayBounds);

		TupleDescInitEntry(desc, attnum, attname,
						   typenameTypeId(entry->typename),
						   atttypmod, attdim, attisset);

		/* Fill in additional stuff not handled by TupleDescInitEntry */
		if (entry->is_not_null)
			constr->has_not_null = true;
		desc->attrs[attnum - 1]->attnotnull = entry->is_not_null;

		/*
		 * Note we copy only pre-cooked default expressions. Digestion of
		 * raw ones is someone else's problem.
		 */
		if (entry->cooked_default != NULL)
		{
			if (attrdef == NULL)
				attrdef = (AttrDefault *) palloc(natts * sizeof(AttrDefault));
			attrdef[ndef].adnum = attnum;
			attrdef[ndef].adbin = pstrdup(entry->cooked_default);
			ndef++;
			desc->attrs[attnum - 1]->atthasdef = true;
		}

		desc->attrs[attnum - 1]->attislocal = entry->is_local;
		desc->attrs[attnum - 1]->attinhcount = entry->inhcount;
	}

	if (constr->has_not_null || ndef > 0)
	{
		desc->constr = constr;

		if (ndef > 0)			/* DEFAULTs */
		{
			if (ndef < natts)
				constr->defval = (AttrDefault *)
					repalloc(attrdef, ndef * sizeof(AttrDefault));
			else
				constr->defval = attrdef;
			constr->num_defval = ndef;
		}
		else
		{
			constr->defval = NULL;
			constr->num_defval = 0;
		}
		constr->check = NULL;
		constr->num_check = 0;
	}
	else
	{
		pfree(constr);
		desc->constr = NULL;
	}
	return desc;
}


/*
 * RelationNameGetTupleDesc
 *
 * Given a (possibly qualified) relation name, build a TupleDesc.
 */
TupleDesc
RelationNameGetTupleDesc(const char *relname)
{
	RangeVar   *relvar;
	Relation	rel;
	TupleDesc	tupdesc;
	List	   *relname_list;

	/* Open relation and get the tuple description */
	relname_list = stringToQualifiedNameList(relname, "RelationNameGetTupleDesc");
	relvar = makeRangeVarFromNameList(relname_list);
	rel = relation_openrv(relvar, AccessShareLock);
	tupdesc = CreateTupleDescCopy(RelationGetDescr(rel));
	relation_close(rel, AccessShareLock);

	return tupdesc;
}

/*
 * TypeGetTupleDesc
 *
 * Given a type Oid, build a TupleDesc.
 *
 * If the type is composite, *and* a colaliases List is provided, *and*
 * the List is of natts length, use the aliases instead of the relation
 * attnames.
 *
 * If the type is a base type, a single item alias List is required.
 */
TupleDesc
TypeGetTupleDesc(Oid typeoid, List *colaliases)
{
	char		functyptype = get_typtype(typeoid);
	TupleDesc	tupdesc = NULL;

	/*
	 * Build a suitable tupledesc representing the output rows
	 */
	if (functyptype == 'c')
	{
		/* Composite data type, i.e. a table's row type */
		Oid			relid = typeidTypeRelid(typeoid);
		Relation	rel;
		int			natts;

		if (!OidIsValid(relid))
			elog(ERROR, "invalid typrelid for complex type %u", typeoid);

		rel = relation_open(relid, AccessShareLock);
		tupdesc = CreateTupleDescCopy(RelationGetDescr(rel));
		natts = tupdesc->natts;
		relation_close(rel, AccessShareLock);
		/* XXX should we hold the lock to ensure table doesn't change? */

		if (colaliases != NIL)
		{
			int			varattno;

			/* does the list length match the number of attributes? */
			if (length(colaliases) != natts)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("number of aliases does not match number of columns")));

			/* OK, use the aliases instead */
			for (varattno = 0; varattno < natts; varattno++)
			{
				char	   *label = strVal(nth(varattno, colaliases));

				if (label != NULL)
					namestrcpy(&(tupdesc->attrs[varattno]->attname), label);
			}
		}
	}
	else if (functyptype == 'b' || functyptype == 'd')
	{
		/* Must be a base data type, i.e. scalar */
		char	   *attname;

		/* the alias list is required for base types */
		if (colaliases == NIL)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("no column alias was provided")));

		/* the alias list length must be 1 */
		if (length(colaliases) != 1)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("number of aliases does not match number of columns")));

		/* OK, get the column alias */
		attname = strVal(lfirst(colaliases));

		tupdesc = CreateTemplateTupleDesc(1, false);
		TupleDescInitEntry(tupdesc,
						   (AttrNumber) 1,
						   attname,
						   typeoid,
						   -1,
						   0,
						   false);
	}
	else if (functyptype == 'p' && typeoid == RECORDOID)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("could not determine row description for function returning record")));
	else
	{
		/* crummy error message, but parser should have caught this */
		elog(ERROR, "function in FROM has unsupported return type");
	}

	return tupdesc;
}