Function transformColumnRef

src/backend/parser/parse_expr.c:473–856

* Transform a ColumnRef. * * If you find yourself changing this code, see also ExpandColumnRefStar. */

 * If you find yourself changing this code, see also ExpandColumnRefStar.
 */
static Node *
transformColumnRef(ParseState *pstate, ColumnRef *cref)
{
	Node	   *node = NULL;
	char	   *nspname = NULL;
	char	   *relname = NULL;
	char	   *colname = NULL;
	ParseNamespaceItem *nsitem;
	int			levels_up;
	enum
	{
		CRERR_NO_COLUMN,
		CRERR_NO_RTE,
		CRERR_WRONG_DB,
		CRERR_TOO_MANY
	}			crerr = CRERR_NO_COLUMN;
	const char *err;

	/*
	 * Check to see if the column reference is in an invalid place within the
	 * query.  We allow column references in most places, except in default
	 * expressions and partition bound expressions.
	 */
	err = NULL;
	switch (pstate->p_expr_kind)
	{
		case EXPR_KIND_NONE:
			Assert(false);		/* can't happen */
			break;
		case EXPR_KIND_OTHER:
		case EXPR_KIND_JOIN_ON:
		case EXPR_KIND_JOIN_USING:
		case EXPR_KIND_FROM_SUBSELECT:
		case EXPR_KIND_FROM_FUNCTION:
		case EXPR_KIND_WHERE:
		case EXPR_KIND_POLICY:
		case EXPR_KIND_HAVING:
		case EXPR_KIND_FILTER:
		case EXPR_KIND_WINDOW_PARTITION:
		case EXPR_KIND_WINDOW_ORDER:
		case EXPR_KIND_WINDOW_FRAME_RANGE:
		case EXPR_KIND_WINDOW_FRAME_ROWS:
		case EXPR_KIND_WINDOW_FRAME_GROUPS:
		case EXPR_KIND_SELECT_TARGET:
		case EXPR_KIND_INSERT_TARGET:
		case EXPR_KIND_UPDATE_SOURCE:
		case EXPR_KIND_UPDATE_TARGET:
		case EXPR_KIND_GROUP_BY:
		case EXPR_KIND_ORDER_BY:
		case EXPR_KIND_DISTINCT_ON:
		case EXPR_KIND_LIMIT:
		case EXPR_KIND_OFFSET:
		case EXPR_KIND_RETURNING:
		case EXPR_KIND_VALUES:
		case EXPR_KIND_VALUES_SINGLE:
		case EXPR_KIND_CHECK_CONSTRAINT:
		case EXPR_KIND_DOMAIN_CHECK:
		case EXPR_KIND_FUNCTION_DEFAULT: