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# SQL code generation
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import copy
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import operator
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import re
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import UserDict
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import dicts
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import iters
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import lists
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import objects
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import strings
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import util
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##### Names
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identifier_max_len = 63 # works for both PostgreSQL and MySQL
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def add_suffix(str_, suffix):
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    '''Preserves version so that it won't be truncated off the string, leading
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    to collisions.'''
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    # Preserve version
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    before, sep, version = str_.rpartition('#')
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    if sep != '': # found match
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        str_ = before
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        suffix = sep+version+suffix
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    return strings.add_suffix(str_, suffix, identifier_max_len)
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def truncate(str_): return add_suffix(str_, '')
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def is_safe_name(name):
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    '''A name is safe *and unambiguous* if it:
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    * contains only *lowercase* word (\w) characters
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    * doesn't start with a digit
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    * contains "_", so that it's not a keyword
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    '''
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    return re.match(r'^(?=.*_)(?!\d)[^\WA-Z]+$', name)
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def esc_name(name, quote='"'):
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    return quote + name.replace(quote, quote+quote) + quote
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        # doubling an embedded quote escapes it in both PostgreSQL and MySQL
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def clean_name(name): return name.replace('"', '').replace('`', '')
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##### General SQL code objects
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class MockDb:
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    def esc_value(self, value): return strings.repr_no_u(value)
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    def esc_name(self, name): return esc_name(name)
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    def col_info(self, col):
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        return TypedCol(col.name, '<type>', CustomCode('<default>'), True)
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mockDb = MockDb()
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class BasicObject(objects.BasicObject):
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    def __init__(self, value): self.value = value
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    def __str__(self): return clean_name(strings.repr_no_u(self))
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##### Unparameterized code objects
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class Code(BasicObject):
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    def to_str(self, db): raise NotImplementedError()
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    def __repr__(self): return self.to_str(mockDb)
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class CustomCode(Code):
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    def __init__(self, str_): self.str_ = str_
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    def to_str(self, db): return self.str_
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def as_Code(value, db=None):
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    '''
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    @param db If set, runs db.std_code() on the value.
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    '''
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    if util.is_str(value):
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        if db != None: value = db.std_code(value)
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        return CustomCode(value)
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    else: return Literal(value)
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class Expr(Code):
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    def __init__(self, expr): self.expr = expr
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    def to_str(self, db): return '('+self.expr.to_str(db)+')'
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##### Literal values
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class Literal(Code):
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    def __init__(self, value): self.value = value
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    def to_str(self, db): return db.esc_value(self.value)
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def as_Value(value):
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    if isinstance(value, Code): return value
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    else: return Literal(value)
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def is_null(value): return isinstance(value, Literal) and value.value == None
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##### Derived elements
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src_self = object() # tells Col that it is its own source column
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class Derived(Code):
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    def __init__(self, srcs):
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        '''An element which was derived from some other element(s).
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        @param srcs See self.set_srcs()
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        '''
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        self.set_srcs(srcs)
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    def set_srcs(self, srcs, overwrite=True):
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        '''
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        @param srcs (self_type...)|src_self The element(s) this is derived from
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        '''
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        if not overwrite and self.srcs != (): return # already set
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        if srcs == src_self: srcs = (self,)
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        srcs = tuple(srcs) # make Col hashable
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        self.srcs = srcs
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    def _compare_on(self):
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        compare_on = self.__dict__.copy()
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        del compare_on['srcs'] # ignore
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        return compare_on
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def cols_srcs(cols): return lists.uniqify(iters.flatten((v.srcs for v in cols)))
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##### Tables
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class Table(Derived):
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    def __init__(self, name, schema=None, srcs=()):
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        '''
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        @param schema str|None (for no schema)
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        @param srcs (Table...)|src_self See Derived.set_srcs()
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        '''
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        Derived.__init__(self, srcs)
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        name = truncate(name)
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        self.name = name
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        self.schema = schema
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    def to_str(self, db):
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        str_ = ''
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        if self.schema != None: str_ += db.esc_name(self.schema)+'.'
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        str_ += db.esc_name(self.name)
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        return str_
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    def to_Table(self): return self
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def is_underlying_table(table):
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    return isinstance(table, Table) and table.to_Table() is table
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class NoUnderlyingTableException(Exception): pass
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def underlying_table(table):
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    table = remove_table_rename(table)
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    if not is_underlying_table(table): raise NoUnderlyingTableException
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    return table
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def as_Table(table, schema=None):
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    if table == None or isinstance(table, Code): return table
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    else: return Table(table, schema)
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def suffixed_table(table, suffix): return Table(table.name+suffix, table.schema)
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class NamedTable(Table):
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    def __init__(self, name, code, cols=None):
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        Table.__init__(self, name)
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        if not isinstance(code, Code): code = Table(code)
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        if not isinstance(code, (Table, FunctionCall, Expr)): code = Expr(code)
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        if cols != None: cols = map(to_name_only_col, cols)
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        self.code = code
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        self.cols = cols
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    def to_str(self, db):
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        str_ = self.code.to_str(db)+'\nAS '+Table.to_str(self, db)
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        if self.cols != None:
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            str_ += ' ('+(', '.join((c.to_str(db) for c in self.cols)))+')'
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        return str_
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    def to_Table(self): return Table(self.name)
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def remove_table_rename(table):
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    if isinstance(table, NamedTable): table = table.code
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    return table
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##### Columns
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class Col(Derived):
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    def __init__(self, name, table=None, srcs=()):
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        '''
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        @param table Table|None (for no table)
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        @param srcs (Col...)|src_self See Derived.set_srcs()
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        '''
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        Derived.__init__(self, srcs)
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        name = truncate(name)
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        if util.is_str(table): table = Table(table)
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        assert table == None or isinstance(table, Table)
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        self.name = name
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        self.table = table
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    def to_str(self, db):
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        str_ = ''
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        if self.table != None: str_ += self.table.to_Table().to_str(db)+'.'
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        str_ += db.esc_name(self.name)
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        return str_
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    def to_Col(self): return self
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def is_table_col(col): return isinstance(col, Col) and col.table != None
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def as_Col(col, table=None, name=None):
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    '''
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    @param name If not None, any non-Col input will be renamed using NamedCol.
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    '''
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    if name != None:
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        col = as_Value(col)
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        if not isinstance(col, Col): col = NamedCol(name, col)
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    if isinstance(col, Code): return col
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    else: return Col(col, table)
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def with_default_table(col, table, overwrite=False):
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    col = as_Col(col)
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    if not isinstance(col, NamedCol) and (overwrite or col.table == None):
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        col = copy.copy(col) # don't modify input!
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        col.table = table
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    return col
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def set_cols_table(table, cols):
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    table = as_Table(table)
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    for i, col in enumerate(cols):
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        col = cols[i] = as_Col(col)
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        col.table = table
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def to_name_only_col(col, check_table=None):
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    col = as_Col(col)
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    if not isinstance(col, Col): return col
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    if check_table != None:
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        table = col.table
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        assert table == None or table == check_table
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    return Col(col.name)
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class NamedCol(Col):
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    def __init__(self, name, code):
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        Col.__init__(self, name)
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        if not isinstance(code, Code): code = Literal(code)
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        self.code = code
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    def to_str(self, db):
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        return self.code.to_str(db)+' AS '+Col.to_str(self, db)
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    def to_Col(self): return Col(self.name)
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def remove_col_rename(col):
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    if isinstance(col, NamedCol): col = col.code
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    return col
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def underlying_col(col):
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    col = remove_col_rename(col)
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    if not isinstance(col, Col): raise NoUnderlyingTableException
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    return Col(col.name, underlying_table(col.table), col.srcs)
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def wrap(wrap_func, value):
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    '''Wraps a value, propagating any column renaming to the returned value.'''
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    if isinstance(value, NamedCol):
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        return NamedCol(value.name, wrap_func(value.code))
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    else: return wrap_func(value)
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class ColDict(dicts.DictProxy):
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    '''A dict that automatically makes inserted entries Col objects'''
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    def __init__(self, db, keys_table, dict_={}):
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        dicts.DictProxy.__init__(self, {})
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        keys_table = as_Table(keys_table)
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        self.db = db
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        self.table = keys_table
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        self.update(dict_) # after setting vars because __setitem__() needs them
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    def copy(self): return ColDict(self.db, self.table, self.inner.copy())
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    def __getitem__(self, key):
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        return dicts.DictProxy.__getitem__(self, self._key(key))
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    def __setitem__(self, key, value):
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        key = self._key(key)
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        if value == None: value = self.db.col_info(key).default
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        dicts.DictProxy.__setitem__(self, key, as_Col(value, name=key.name))
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    def _key(self, key): return as_Col(key, self.table)
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##### Functions
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Function = Table
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as_Function = as_Table
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class InternalFunction(CustomCode): pass
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class FunctionCall(Code):
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    def __init__(self, function, *args):
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        '''
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        @param args [Code|literal-value...] The function's arguments
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        '''
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        if not isinstance(function, Code): function = Function(function)
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        args = map(remove_col_rename, map(as_Value, args))
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        self.function = function
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        self.args = args
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    def to_str(self, db):
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        args_str = ', '.join((v.to_str(db) for v in self.args))
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        return self.function.to_str(db)+'('+args_str+')'
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def wrap_in_func(function, value):
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    '''Wraps a value inside a function call.
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    Propagates any column renaming to the returned value.
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    '''
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    return wrap(lambda v: FunctionCall(function, v), value)
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def unwrap_func_call(func_call, check_name=None):
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    '''Unwraps any function call to its first argument.
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    Also removes any column renaming.
337
    '''
338
    func_call = remove_col_rename(func_call)
339
    if not isinstance(func_call, FunctionCall): return func_call
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    if check_name != None:
342
        name = func_call.function.name
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        assert name == None or name == check_name
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    return func_call.args[0]
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##### Conditions
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class ColValueCond(Code):
349
    def __init__(self, col, value):
350
        value = as_ValueCond(value)
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        self.col = col
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        self.value = value
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    def to_str(self, db): return self.value.to_str(db, self.col)
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def combine_conds(conds, keyword=None):
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    '''
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    @param keyword The keyword to add before the conditions, if any
360
    '''
361
    str_ = ''
362
    if keyword != None:
363
        if conds == []: whitespace = ''
364
        elif len(conds) == 1: whitespace = ' '
365
        else: whitespace = '\n'
366
        str_ += keyword+whitespace
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    str_ += '\nAND '.join(conds)
369
    return str_
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##### Condition column comparisons
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class ValueCond(BasicObject):
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    def __init__(self, value):
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        value = remove_col_rename(as_Value(value))
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        self.value = value
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    def to_str(self, db, left_value):
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        '''
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        @param left_value The Code object that the condition is being applied on
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        '''
383
        raise NotImplemented()
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    def __repr__(self): return self.to_str(mockDb, '<left_value>')
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class CompareCond(ValueCond):
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    def __init__(self, value, operator='='):
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        '''
390
        @param operator By default, compares NULL values literally. Use '~=' or
391
            '~!=' to pass NULLs through.
392
        '''
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        ValueCond.__init__(self, value)
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        self.operator = operator
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    def to_str(self, db, left_value):
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        left_value = remove_col_rename(as_Col(left_value))
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        right_value = self.value
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        # Parse operator
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        operator = self.operator
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        passthru_null_ref = [False]
404
        operator = strings.remove_prefix('~', operator, passthru_null_ref)
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        neg_ref = [False]
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        operator = strings.remove_prefix('!', operator, neg_ref)
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        equals = operator.endswith('=') # also includes <=, >=
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        # Handle nullable columns
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        check_null = False
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        if not passthru_null_ref[0]: # NULLs compare equal
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            try: left_value = ensure_not_null(db, left_value)
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            except ensure_not_null_excs: # fall back to alternate method
414
                check_null = equals and isinstance(right_value, Col)
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            else:
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                if isinstance(left_value, EnsureNotNull):
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                    right_value = ensure_not_null(db, right_value,
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                        left_value.type) # apply same function to both sides
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        if equals and is_null(right_value): operator = 'IS'
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        left = left_value.to_str(db)
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        right = right_value.to_str(db)
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        # Create str
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        str_ = left+' '+operator+' '+right
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        if check_null:
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            str_ = '('+str_+' OR ('+left+' IS NULL AND '+right+' IS NULL))'
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        if neg_ref[0]: str_ = 'NOT '+str_
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        return str_
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# Tells as_ValueCond() to assume a non-ValueCond is a literal value
433
assume_literal = object()
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435
def as_ValueCond(value, default_table=assume_literal):
436
    if not isinstance(value, ValueCond):
437
        if default_table is not assume_literal:
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            value = with_default_table(value, default_table)
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        return CompareCond(value)
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    else: return value
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##### Joins
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join_same = object() # tells Join the left and right columns have the same name
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# Tells Join the left and right columns have the same name and are never NULL
447
join_same_not_null = object()
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filter_out = object() # tells Join to filter out rows that match the join
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class Join(BasicObject):
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    def __init__(self, table, mapping={}, type_=None):
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        '''
454
        @param mapping dict(right_table_col=left_table_col, ...)
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            * if left_table_col is join_same: left_table_col = right_table_col
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              * Note that right_table_col must be a string
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            * if left_table_col is join_same_not_null:
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              left_table_col = right_table_col and both have NOT NULL constraint
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              * Note that right_table_col must be a string
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        @param type_ None (for plain join)|str (e.g. 'LEFT')|filter_out
461
            * filter_out: equivalent to 'LEFT' with the query filtered by
462
              `table_pkey IS NULL` (indicating no match)
463
        '''
464
        if util.is_str(table): table = Table(table)
465
        assert type_ == None or util.is_str(type_) or type_ is filter_out
466
467
        self.table = table
468
        self.mapping = mapping
469
        self.type_ = type_
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    def to_str(self, db, left_table_):
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        def join(entry):
473
            '''Parses non-USING joins'''
474
            right_table_col, left_table_col = entry
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            # Switch order (right_table_col is on the left in the comparison)
477
            left = right_table_col
478
            right = left_table_col
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            left_table = self.table
480
            right_table = left_table_
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            # Parse left side
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            left = with_default_table(left, left_table)
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            # Parse special values
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            left_on_right = Col(left.name, right_table)
487
            if right is join_same: right = left_on_right
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            elif right is join_same_not_null:
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                right = CompareCond(left_on_right, '~=')
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            # Parse right side
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            right = as_ValueCond(right, right_table)
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            return right.to_str(db, left)
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        # Create join condition
497
        type_ = self.type_
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        joins = self.mapping
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        if joins == {}: join_cond = None
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        elif type_ is not filter_out and reduce(operator.and_,
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            (v is join_same_not_null for v in joins.itervalues())):
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            # all cols w/ USING, so can use simpler USING syntax
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            cols = map(to_name_only_col, joins.iterkeys())
504
            join_cond = 'USING ('+(', '.join((c.to_str(db) for c in cols)))+')'
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        else: join_cond = combine_conds(map(join, joins.iteritems()), 'ON')
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        if isinstance(self.table, NamedTable): whitespace = '\n'
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        else: whitespace = ' '
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        # Create join
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        if type_ is filter_out: type_ = 'LEFT'
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        str_ = ''
513
        if type_ != None: str_ += type_+' '
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        str_ += 'JOIN'+whitespace+self.table.to_str(db)
515
        if join_cond != None: str_ += whitespace+join_cond
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        return str_
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    def __repr__(self): return self.to_str(mockDb, '<left_table>')
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##### Value exprs
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default = CustomCode('DEFAULT')
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row_count = CustomCode('count(*)')
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# See <http://www.postgresql.org/docs/8.3/static/datatype-numeric.html>
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null_sentinels = {'integer': 2147483647, 'text': r'\N',
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    'character varying': r'\N'}
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class EnsureNotNull(FunctionCall):
531
    def __init__(self, value, type_):
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        FunctionCall.__init__(self, InternalFunction('COALESCE'), as_Col(value),
533 2850 aaronmk
            null_sentinels[type_])
534
535
        self.type = type_
536
537 2737 aaronmk
##### Table exprs
538
539
class Values(Code):
540
    def __init__(self, values):
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        '''
542
        @param values [...]|[[...], ...] Can be one or multiple rows.
543
        '''
544
        rows = values
545
        if len(values) >= 1 and not lists.is_seq(values[0]): # only one row
546
            rows = [values]
547
        for i, row in enumerate(rows):
548
            rows[i] = map(remove_col_rename, map(as_Value, row))
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        self.rows = rows
551 2737 aaronmk
552
    def to_str(self, db):
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        def row_str(row):
554
            return '('+(', '.join((v.to_str(db) for v in row)))+')'
555
        return 'VALUES '+(', '.join(map(row_str, self.rows)))
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557 2740 aaronmk
def NamedValues(name, cols, values):
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    '''
559
    @post `cols` will be changed to Col objects with the table set to `name`.
560
    '''
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    table = NamedTable(name, Values(values), cols)
562
    set_cols_table(table, cols)
563
    return table
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565 2674 aaronmk
##### Database structure
566
567
class TypedCol(Col):
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    def __init__(self, name, type_, default=None, nullable=True,
569
        constraints=None):
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        assert default == None or isinstance(default, Code)
571
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        Col.__init__(self, name)
573
574
        self.type = type_
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        self.default = default
576
        self.nullable = nullable
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        self.constraints = constraints
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579 2818 aaronmk
    def to_str(self, db):
580
        str_ = Col.to_str(self, db)+' '+self.type
581
        if not self.nullable: str_ += ' NOT NULL'
582
        if self.default != None: str_ += ' DEFAULT '+self.default.to_str(db)
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        if self.constraints != None: str_ += ' '+self.constraints
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        return str_
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586
    def to_Col(self): return Col(self.name)
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588 2840 aaronmk
ensure_not_null_excs = (NoUnderlyingTableException, KeyError)
589
590 2851 aaronmk
def ensure_not_null(db, col, type_=None):
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    '''
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    @param col If type_ is not set, must have an underlying column.
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    @param type_ If set, overrides the underlying column's type.
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    @return EnsureNotNull|Col
595
    @throws ensure_not_null_excs
596
    '''
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    nullable = True
598
    try: typed_col = db.col_info(underlying_col(col))
599
    except NoUnderlyingTableException:
600
        if type_ == None: raise
601
    else:
602
        if type_ == None: type_ = typed_col.type
603
        nullable = typed_col.nullable
604
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    if nullable: col = EnsureNotNull(col, type_)
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    return col