# SQL code generation

import lists

    to collisions.'''

    before, sep, version = str_.rpartition('#')

    if sep != '': # found match

        str_ = before

    * contains only *lowercase* word (\w) characters

    * doesn't start with a digit

    * contains "_", so that it's not a keyword

    '''

    return re.match(r'^(?=.*_)(?!\d)[^\WA-Z]+$', name)

    return quote + name.replace(quote, quote+quote) + quote

        # doubling an embedded quote escapes it in both PostgreSQL and MySQL

    def col_info(self, col):

        return TypedCol(col.name, '<type>', CustomCode('<default>'), True)

    def __init__(self, value): self.value = value

    def __str__(self): return clean_name(strings.repr_no_u(self))

    def to_str(self, db): return self.str_

    '''

    @param db If set, runs db.std_code() on the value.

    '''

    if util.is_str(value):

        if db != None: value = db.std_code(value)

        return CustomCode(value)

    def __init__(self, expr): self.expr = expr

    def to_str(self, db): return '('+self.expr.to_str(db)+')'

    def to_str(self, db): return db.esc_value(self.value)

    if isinstance(value, Code): return value

    else: return Literal(value)

src_self = object() # tells Col that it is its own source column

class Derived(Code):

    def __init__(self, srcs):

        '''

        self.set_srcs(srcs)

        @param srcs (self_type...)|src_self The element(s) this is derived from

        '''

        srcs = tuple(srcs) # make Col hashable

        self.srcs = srcs

    def _compare_on(self):

        compare_on = self.__dict__.copy()

        del compare_on['srcs'] # ignore

        return compare_on

def cols_srcs(cols): return lists.uniqify(iters.flatten((v.srcs for v in cols)))

    def __init__(self, name, schema=None, srcs=()):

        @param schema str|None (for no schema)

        self.schema = schema

        str_ = ''

        if self.schema != None: str_ += db.esc_name(self.schema)+'.'

        str_ += db.esc_name(self.name)

        return str_

    def to_Table(self): return self

    return isinstance(table, Table) and table.to_Table() is table

def underlying_table(table):

    table = remove_table_rename(table)

    if not is_underlying_table(table): raise NoUnderlyingTableException

    return table

    def __init__(self, name, code, cols=None):

        Table.__init__(self, name)

        if not isinstance(code, Code): code = Table(code)

        self.code = code

        self.cols = cols

    def to_str(self, db):

            str_ += ' ('+(', '.join((c.to_str(db) for c in self.cols)))+')'

    def to_Table(self): return Table(self.name)

    if isinstance(table, NamedTable): table = table.code

    return table

        @param table Table|None (for no table)

        self.name = name

        self.table = table

        str_ = db.esc_name(self.name)

        if self.table != None:

            str_ = '.'+str_

            table_str = self.table.to_Table().to_str(db)

            if use_concat: str_ = concat(table_str, str_)

            else: str_ = table_str+str_

    '''

    @param name If not None, any non-Col input will be renamed using NamedCol.

    '''

    if name != None:

        col = as_Value(col)

        if not isinstance(col, Col): col = NamedCol(name, col)

    if isinstance(col, Code): return col

        col.table = table

    table = as_Table(table)

    for i, col in enumerate(cols):

        col = cols[i] = as_Col(col)

        col.table = table

    col = as_Col(col)

    if check_table != None:

        table = col.table

        assert table == None or table == check_table

    return Col(col.name)

        self.code = code

    def to_str(self, db):

    def to_Col(self): return Col(self.name)

    if isinstance(col, NamedCol): col = col.code

    return col

    col = remove_col_rename(col)

    '''Wraps a value, propagating any column renaming to the returned value.'''

    if isinstance(value, NamedCol):

        return NamedCol(value.name, wrap_func(value.code))

    else: return wrap_func(value)

        return dicts.DictProxy.__getitem__(self, self._key(key))

    def __init__(self, name, value):

        NamedCol.__init__(self, name, value)

    def to_str(self, db):

        return Col.to_str(self, db)+' := '+self.code.to_str(db)

        if not isinstance(function, Code): function = Function(function)

        args = map(filter_, args)

        args += [NamedArg(k, filter_(v)) for k, v in kw_args.iteritems()]

        self.function = function

        self.args = args

    def to_str(self, db):

        args_str = ', '.join((v.to_str(db) for v in self.args))

        return self.function.to_str(db)+'('+args_str+')'

    '''Wraps a value inside a function call.

    Propagates any column renaming to the returned value.

    '''

    '''Unwraps any function call to its first argument.

    Also removes any column renaming.

    '''

    func_call = remove_col_rename(func_call)

    if not isinstance(func_call, FunctionCall): return func_call

    if check_name != None:

        name = func_call.function.name

        assert name == None or name == check_name

    return func_call.args[0]

    def __init__(self, col, value):

        value = as_ValueCond(value)

        self.col = col

        self.value = value

    def to_str(self, db): return self.value.to_str(db, self.col)

    '''

    @param keyword The keyword to add before the conditions, if any

    '''

    str_ = ''

    if keyword != None:

        if conds == []: whitespace = ''

        elif len(conds) == 1: whitespace = ' '

        else: whitespace = '\n'

        str_ += keyword+whitespace

    str_ += '\nAND '.join(conds)

    return str_

        self.value = value

        raise NotImplemented()

class CompareCond(ValueCond):

    def __init__(self, value, operator='='):

        @param operator By default, compares NULL values literally. Use '~=' or

            '~!=' to pass NULLs through.

        '''

        self.operator = operator

        # Parse operator

        operator = strings.remove_prefix('~', operator, passthru_null_ref)

        neg_ref = [False]

        operator = strings.remove_prefix('!', operator, neg_ref)

        check_null = False

                check_null = equals and isinstance(right_value, Col)

                    right_value = ensure_not_null(db, right_value,

                        left_value.type) # apply same function to both sides

        right = right_value.to_str(db)

        str_ = left+' '+operator+' '+right

        if neg_ref[0]: str_ = 'NOT '+str_

assume_literal = object()

def as_ValueCond(value, default_table=assume_literal):

    if not isinstance(value, ValueCond):

        if default_table is not assume_literal:

join_same_not_null = object()

        @param mapping dict(right_table_col=left_table_col, ...)

            * if left_table_col is join_same_not_null:

              left_table_col = right_table_col and both have NOT NULL constraint

              * Note that right_table_col must be a string

            * filter_out: equivalent to 'LEFT' with the query filtered by

              `table_pkey IS NULL` (indicating no match)

        '''

        if util.is_str(table): table = Table(table)

        assert type_ == None or util.is_str(type_) or type_ is filter_out

        self.table = table

        self.mapping = mapping

        self.type_ = type_

            '''Parses non-USING joins'''

            right_table_col, left_table_col = entry

            left = right_table_col

            right = left_table_col

            right_table = left_table_

            if right is join_same: right = left_on_right

            return right.to_str(db, left)

        type_ = self.type_

        elif type_ is not filter_out and reduce(operator.and_,

            join_cond = 'USING ('+(', '.join((c.to_str(db) for c in cols)))+')'

        else: whitespace = ' '

        if type_ is filter_out: type_ = 'LEFT'

        if type_ != None: str_ += type_+' '

        if join_cond != None: str_ += whitespace+join_cond

##### Value exprs

    'character varying': r'\N',

    'double precision': 'NaN',

    'integer': 2147483647,

    'text': r'\N',

    'timestamp with time zone': 'infinity'

}

    def __init__(self, value, type_):

        self.type = type_

class Values(Code):

    def __init__(self, values):

        @param values [...]|[[...], ...] Can be one or multiple rows.

        '''

        rows = values

        if len(values) >= 1 and not lists.is_seq(values[0]): # only one row

            rows = [values]

        for i, row in enumerate(rows):

            rows[i] = map(remove_col_rename, map(as_Value, row))

    def to_str(self, db):

            return '('+(', '.join((v.to_str(db) for v in row)))+')'

        return 'VALUES '+(', '.join(map(row_str, self.rows)))

    @post `cols` will be changed to Col objects with the table set to `name`.

    '''

    set_cols_table(table, cols)

    return table

class TypedCol(Col):

        constraints=None):

        self.type = type_

        self.nullable = nullable

        str_ = Col.to_str(self, db)+' '+self.type

        if not self.nullable: str_ += ' NOT NULL'

        if self.default != None: str_ += ' DEFAULT '+self.default.to_str(db)

    def to_Col(self): return Col(self.name)

    @throws ensure_not_null_excs

    '''

    try: typed_col = db.col_info(underlying_col(col))

    except NoUnderlyingTableException:

        if type_ == None: raise

    else:

        if type_ == None: type_ = typed_col.type

        nullable = typed_col.nullable

        try: col = EnsureNotNull(col, type_)

        except KeyError, e:

            # Warn of no null sentinel for type, even if caller catches error

            warnings.warn(UserWarning(exc.str_(e)))