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aaronmk
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# SQL code generation
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import operator
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aaronmk
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import sql
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import strings
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import util
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##### SQL code objects
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class Code:
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def to_str(self, db): raise NotImplemented()
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def __str__(self): return str(self.__dict__)
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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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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 is_null(value): return isinstance(value, Literal) and value.value == None
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class Table(Code):
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def __init__(self, name, schema=None):
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'''
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@param schema str|None (for no schema)
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'''
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self.name = name
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self.schema = schema
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def to_str(self, db): return sql.qual_name(db, self.schema, self.name)
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def as_Table(table):
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if table == None or isinstance(table, Code): return table
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else: return Table(table)
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class Col(Code):
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def __init__(self, name, table=None):
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'''
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@param table Table|None (for no table)
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'''
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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_str(db)+'.'
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str_ += sql.esc_name(db, self.name)
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return str_
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def as_Col(col, table=None):
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if col == None or isinstance(col, Code): return col
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else: return Col(col, table)
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class NamedCode(Code):
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def __init__(self, name, code):
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if not isinstance(code, Code): code = Literal(code)
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self.name = name
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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 '+sql.esc_name(db, self.name)
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##### Parameterized SQL code objects
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class ValueCond:
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def __init__(self, value):
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if not isinstance(value, Code): value = Literal(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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'''
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raise NotImplemented()
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def __str__(self): return str(self.__dict__)
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class CompareCond(ValueCond):
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def __init__(self, value, operator='='):
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'''
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@param operator By default, compares NULL values literally. Use '~=' or
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'~!=' to pass NULLs through.
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'''
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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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if not isinstance(left_value, Code): left_value = Col(left_value)
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right_value = self.value
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left = left_value.to_str(db)
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right = right_value.to_str(db)
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# Parse operator
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operator = self.operator
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passthru_null_ref = [False]
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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('=')
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if equals and is_null(self.value): operator = 'IS'
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# Create str
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str_ = left+' '+operator+' '+right
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if equals and not passthru_null_ref[0] and isinstance(right_value, Col):
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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
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assume_literal = object()
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def as_ValueCond(value, default_table=assume_literal):
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if not isinstance(value, ValueCond):
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if default_table is not assume_literal:
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value = as_Col(value, default_table)
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return CompareCond(value)
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else: return value
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join_using = object() # tells Join to join the column with USING
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filter_out = object() # tells Join to filter out rows that match the join
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class Join(Code):
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def __init__(self, table, mapping, type_=None):
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'''
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@param mapping dict(right_table_col=left_table_col, ...)
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* if left_table_col is join_using: left_table_col = right_table_col
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@param type_ None (for plain join)|str (e.g. 'LEFT')|filter_out
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* filter_out: equivalent to 'LEFT' with the query filtered by
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`table_pkey IS NULL` (indicating no match)
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'''
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if util.is_str(table): table = Table(table)
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assert type_ == None or util.is_str(type_) or type_ is filter_out
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self.table = table
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self.mapping = mapping
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self.type_ = type_
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def to_str(self, db, left_table):
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def join(entry):
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'''Parses non-USING joins'''
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right_table_col, left_table_col = entry
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# Parse special values
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if left_table_col is join_using: left_table_col = right_table_col
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cond = as_ValueCond(right_table_col, self.table)
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return cond.to_str(db, as_Col(left_table_col, left_table))
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# Create join condition
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type_ = self.type_
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joins = self.mapping
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if type_ is not filter_out and reduce(operator.and_,
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(v is join_using for v in joins.itervalues())):
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# all cols w/ USING, so can use simpler USING syntax
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cols = (as_Col(v).to_str(db) for v in joins.iterkeys())
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join_cond = 'USING ('+(', '.join(cols))+')'
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else: join_cond = 'ON '+(' AND '.join(map(join, joins.iteritems())))
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# Create join
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if type_ is filter_out: type_ = 'LEFT'
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str_ = ''
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if type_ != None: str_ += type_+' '
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str_ += 'JOIN '+self.table.to_str(db)+' '+join_cond
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return str_
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