Function ATPrepAddColumn

src/backend/commands/tablecmds.c:8279–8294

* ALTER TABLE ADD COLUMN * * Adds an additional attribute to a relation making the assumption that * CHECK, NOT NULL, and FOREIGN KEY constraints will be removed from the * AT_AddColumn AlterTableCmd by parse_utilcmd.c and added as independent * AlterTableCmd's. * * ADD COLUMN cannot use the normal ALTER TABLE recursion mechanism, because we * have to decide at runtime whether to recurse o

 * situations correctly.)
 */
static void
ATPrepAddColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
				bool is_view, AlterTableCmd *cmd, LOCKMODE lockmode,
				AlterTableUtilityContext *context)
{
	if (rel->rd_rel->reloftype && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot add column to typed table")));

	if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
		ATTypedTableRecursion(wqueue, rel, cmd, lockmode, context);

	if (recurse && !is_view)
		cmd->subtype = AT_AddColumnRecurse;
}

/*
 * Add a column to a table.  The return value is the address of the