compiler.py

SQLAlchemy. 经典的Python ORM框架。学习必看。

    def visit_unary(self, unary, **kwargs):
        s = self.process(unary.element)
        if unary.operator:
            s = self.operator_string(unary.operator) + " " + s
        if unary.modifier:
            s = s + " " + self.operator_string(unary.modifier)
        return s

    def visit_binary(self, binary, **kwargs):
        op = self.operator_string(binary.operator)
        if callable(op):
            return op(self.process(binary.left), self.process(binary.right))
        else:
            return self.process(binary.left) + " " + op + " " + self.process(binary.right)

    def operator_string(self, operator):
        return self.operators.get(operator, str(operator))

    def visit_bindparam(self, bindparam, **kwargs):
        name = self._truncate_bindparam(bindparam)
        if name in self.binds:
            existing = self.binds[name]
            if existing is not bindparam and (existing.unique or bindparam.unique):
                raise exceptions.CompileError("Bind parameter '%s' conflicts with unique bind parameter of the same name" % bindparam.key)
        self.binds[bindparam.key] = self.binds[name] = bindparam
        return self.bindparam_string(name)

    def _truncate_bindparam(self, bindparam):
        if bindparam in self.bind_names:
            return self.bind_names[bindparam]

        bind_name = bindparam.key
        bind_name = self._truncated_identifier("bindparam", bind_name)
        # add to bind_names for translation
        self.bind_names[bindparam] = bind_name

        return bind_name

    def _truncated_identifier(self, ident_class, name):
        if (ident_class, name) in self.generated_ids:
            return self.generated_ids[(ident_class, name)]

        anonname = ANONYMOUS_LABEL.sub(self._process_anon, name)

        if len(anonname) > self.dialect.max_identifier_length:
            counter = self.generated_ids.get(ident_class, 1)
            truncname = anonname[0:self.dialect.max_identifier_length - 6] + "_" + hex(counter)[2:]
            self.generated_ids[ident_class] = counter + 1
        else:
            truncname = anonname
        self.generated_ids[(ident_class, name)] = truncname
        return truncname

    def _process_anon(self, match):
        (ident, derived) = match.group(1,2)
        key = ('anonymous', ident)
        if key in self.generated_ids:
            return self.generated_ids[key]
        else:
            anonymous_counter = self.generated_ids.get(('anon_counter', derived), 1)
            newname = derived + "_" + str(anonymous_counter)
            self.generated_ids[('anon_counter', derived)] = anonymous_counter + 1
            self.generated_ids[key] = newname
            return newname

    def _anonymize(self, name):
        return ANONYMOUS_LABEL.sub(self._process_anon, name)

    def bindparam_string(self, name):
        if self.positional:
            self.positiontup.append(name)

        return self.bindtemplate % {'name':name, 'position':len(self.positiontup)}

    def visit_alias(self, alias, asfrom=False, **kwargs):
        if asfrom:
            return self.process(alias.original, asfrom=True, **kwargs) + " AS " + self.preparer.format_alias(alias, self._anonymize(alias.name))
        else:
            return self.process(alias.original, **kwargs)

    def label_select_column(self, select, column, asfrom):
        """label columns present in a select()."""

        if isinstance(column, sql._Label):
            return column

        if select.use_labels and getattr(column, '_label', None):
            return column.label(column._label)

        if \
            asfrom and \
            isinstance(column, sql._ColumnClause) and \
            not column.is_literal and \
            column.table is not None and \
            not isinstance(column.table, sql.Select):
            return column.label(column.name)
        elif not isinstance(column, (sql._UnaryExpression, sql._TextClause)) and (not hasattr(column, 'name') or isinstance(column, sql._Function)):
            return column.anon_label
        else:
            return column

    def visit_select(self, select, asfrom=False, parens=True, iswrapper=False, **kwargs):

        stack_entry = {'select':select}
        prev_entry = self.stack and self.stack[-1] or None

        if asfrom or (prev_entry and 'select' in prev_entry):
            stack_entry['is_subquery'] = True
            if prev_entry and 'iswrapper' in prev_entry:
                column_clause_args = {'result_map':self.result_map}
            else:
                column_clause_args = {}
        elif iswrapper:
            column_clause_args = {}
            stack_entry['iswrapper'] = True
        else:
            column_clause_args = {'result_map':self.result_map}

        if self.stack and 'from' in self.stack[-1]:
            existingfroms = self.stack[-1]['from']
        else:
            existingfroms = None

        froms = select._get_display_froms(existingfroms)

        correlate_froms = util.Set()
        for f in froms:
            correlate_froms.add(f)
            correlate_froms.update(f._get_from_objects())

        # TODO: might want to propigate existing froms for select(select(select))
        # where innermost select should correlate to outermost
#        if existingfroms:
#            correlate_froms = correlate_froms.union(existingfroms)
        stack_entry['from'] = correlate_froms
        self.stack.append(stack_entry)

        # the actual list of columns to print in the SELECT column list.
        inner_columns = util.OrderedSet()

        for co in select.inner_columns:
            l = self.label_select_column(select, co, asfrom=asfrom)
            inner_columns.add(self.process(l, **column_clause_args))

        collist = string.join(inner_columns.difference(util.Set([None])), ', ')

        text = " ".join(["SELECT"] + [self.process(x) for x in select._prefixes]) + " "
        text += self.get_select_precolumns(select)
        text += collist

        whereclause = select._whereclause

        from_strings = []
        for f in froms:
            from_strings.append(self.process(f, asfrom=True))

            w = self.get_whereclause(f)
            if w is not None:
                if whereclause is not None:
                    whereclause = sql.and_(w, whereclause)
                else:
                    whereclause = w

        if froms:
            text += " \nFROM "
            text += string.join(from_strings, ', ')
        else:
            text += self.default_from()

        if whereclause is not None:
            t = self.process(whereclause)
            if t:
                text += " \nWHERE " + t

        group_by = self.process(select._group_by_clause)
        if group_by:
            text += " GROUP BY " + group_by

        if select._having is not None:
            t = self.process(select._having)
            if t:
                text += " \nHAVING " + t

        text += self.order_by_clause(select)
        text += (select._limit or select._offset) and self.limit_clause(select) or ""
        text += self.for_update_clause(select)

        self.stack.pop(-1)

        if asfrom and parens:
            return "(" + text + ")"
        else:
            return text

    def get_select_precolumns(self, select):
        """Called when building a ``SELECT`` statement, position is just before column list."""

        return select._distinct and "DISTINCT " or ""

    def order_by_clause(self, select):
        order_by = self.process(select._order_by_clause)
        if order_by:
            return " ORDER BY " + order_by
        else:
            return ""

    def for_update_clause(self, select):
        if select.for_update:
            return " FOR UPDATE"
        else:
            return ""

    def limit_clause(self, select):
        text = ""
        if select._limit is not None:
            text +=  " \n LIMIT " + str(select._limit)
        if select._offset is not None:
            if select._limit is None:
                text += " \n LIMIT -1"
            text += " OFFSET " + str(select._offset)
        return text

    def visit_table(self, table, asfrom=False, **kwargs):
        if asfrom:
            if getattr(table, "schema", None):
                return self.preparer.quote(table, table.schema) + "." + self.preparer.quote(table, table.name)
            else:
                return self.preparer.quote(table, table.name)
        else:
            return ""

    def visit_join(self, join, asfrom=False, **kwargs):
        return (self.process(join.left, asfrom=True) + (join.isouter and " LEFT OUTER JOIN " or " JOIN ") + \
            self.process(join.right, asfrom=True) + " ON " + self.process(join.onclause))

    def visit_sequence(self, seq):
        return None

    def visit_insert(self, insert_stmt):
        self.isinsert = True
        colparams = self._get_colparams(insert_stmt)
        preparer = self.preparer

        return ("INSERT INTO %s (%s) VALUES (%s)" %
                (preparer.format_table(insert_stmt.table),
                 ', '.join([preparer.quote(c[0], c[0].name)
                            for c in colparams]),
                 ', '.join([c[1] for c in colparams])))

    def visit_update(self, update_stmt):
        self.stack.append({'from':util.Set([update_stmt.table])})

        self.isupdate = True
        colparams = self._get_colparams(update_stmt)

        text = "UPDATE " + self.preparer.format_table(update_stmt.table) + " SET " + string.join(["%s=%s" % (self.preparer.quote(c[0], c[0].name), c[1]) for c in colparams], ', ')

        if update_stmt._whereclause:
            text += " WHERE " + self.process(update_stmt._whereclause)

        self.stack.pop(-1)

        return text

    def _get_colparams(self, stmt):
        """create a set of tuples representing column/string pairs for use
        in an INSERT or UPDATE statement.

        """

        def create_bind_param(col, value):
            bindparam = sql.bindparam(col.key, value, type_=col.type)
            self.binds[col.key] = bindparam
            return self.bindparam_string(self._truncate_bindparam(bindparam))

        self.postfetch = []
        self.prefetch = []

        # no parameters in the statement, no parameters in the
        # compiled params - return binds for all columns
        if self.column_keys is None and stmt.parameters is None:
            return [(c, create_bind_param(c, None)) for c in stmt.table.columns]

        # if we have statement parameters - set defaults in the
        # compiled params
        if self.column_keys is None:
            parameters = {}
        else:
            parameters = dict([(getattr(key, 'key', key), None) for key in self.column_keys])

        if stmt.parameters is not None:
            for k, v in stmt.parameters.iteritems():
                parameters.setdefault(getattr(k, 'key', k), v)

        # create a list of column assignment clauses as tuples
        values = []
        for c in stmt.table.columns:
            if c.key in parameters:
                value = parameters[c.key]
                if sql._is_literal(value):
                    value = create_bind_param(c, value)
                else:
                    self.postfetch.append(c)
                    value = self.process(value.self_group())
                values.append((c, value))
            elif isinstance(c, schema.Column):
                if self.isinsert:
                    if (c.primary_key and self.dialect.preexecute_pk_sequences and not self.inline):
                        if (((isinstance(c.default, schema.Sequence) and
                              not c.default.optional) or
                             not self.dialect.supports_pk_autoincrement) or
                            (c.default is not None and
                             not isinstance(c.default, schema.Sequence))):
                            values.append((c, create_bind_param(c, None)))
                            self.prefetch.append(c)
                    elif isinstance(c.default, schema.ColumnDefault):
                        if isinstance(c.default.arg, sql.ClauseElement):
                            values.append((c, self.process(c.default.arg.self_group())))
                            if not c.primary_key:
                                # dont add primary key column to postfetch
                                self.postfetch.append(c)
                        else:
                            values.append((c, create_bind_param(c, None)))
                            self.prefetch.append(c)
                    elif isinstance(c.default, schema.PassiveDefault):
                        if not c.primary_key:
                            self.postfetch.append(c)
                    elif isinstance(c.default, schema.Sequence):
                        proc = self.process(c.default)
                        if proc is not None:
                            values.append((c, proc))
                            if not c.primary_key:
                                self.postfetch.append(c)
                elif self.isupdate:
                    if isinstance(c.onupdate, schema.ColumnDefault):
                        if isinstance(c.onupdate.arg, sql.ClauseElement):
                            values.append((c, self.process(c.onupdate.arg.self_group())))
                            self.postfetch.append(c)
                        else:
                            values.append((c, create_bind_param(c, None)))
                            self.prefetch.append(c)
                    elif isinstance(c.onupdate, schema.PassiveDefault):
                        self.postfetch.append(c)
        return values

    def visit_delete(self, delete_stmt):
        self.stack.append({'from':util.Set([delete_stmt.table])})
        self.isdelete = True

        text = "DELETE FROM " + self.preparer.format_table(delete_stmt.table)

        if delete_stmt._whereclause:
            text += " WHERE " + self.process(delete_stmt._whereclause)

        self.stack.pop(-1)

        return text

    def visit_savepoint(self, savepoint_stmt):
        return "SAVEPOINT %s" % self.preparer.format_savepoint(savepoint_stmt)

    def visit_rollback_to_savepoint(self, savepoint_stmt):
        return "ROLLBACK TO SAVEPOINT %s" % self.preparer.format_savepoint(savepoint_stmt)

    def visit_release_savepoint(self, savepoint_stmt):
        return "RELEASE SAVEPOINT %s" % self.preparer.format_savepoint(savepoint_stmt)

    def __str__(self):
        return self.string or ''

class DDLBase(engine.SchemaIterator):
    def find_alterables(self, tables):
        alterables = []
        class FindAlterables(schema.SchemaVisitor):