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4cfb59bfba
Instead of encoding the conversion behaviour in the model class (via the `_bytes_keys` attribute) we define it on the type. This gives us a more extensible interface and separates logic. This should not change any behaviour (as one can see by closely staring at the code).
768 lines
26 KiB
Python
768 lines
26 KiB
Python
# This file is part of beets.
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# Copyright 2014, Adrian Sampson.
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#
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# Permission is hereby granted, free of charge, to any person obtaining
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# a copy of this software and associated documentation files (the
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# "Software"), to deal in the Software without restriction, including
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# without limitation the rights to use, copy, modify, merge, publish,
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# distribute, sublicense, and/or sell copies of the Software, and to
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# permit persons to whom the Software is furnished to do so, subject to
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# the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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"""The central Model and Database constructs for DBCore.
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"""
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import time
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import os
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from collections import defaultdict
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import threading
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import sqlite3
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import contextlib
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import collections
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import beets
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from beets.util.functemplate import Template
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from .query import MatchQuery, NullSort
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from .types import BASE_TYPE
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class FormattedMapping(collections.Mapping):
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"""A `dict`-like formatted view of a model.
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The accessor `mapping[key]` returns the formated version of
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`model[key]` as a unicode string.
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If `for_path` is true, all path separators in the formatted values
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are replaced.
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"""
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def __init__(self, model, for_path=False):
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self.for_path = for_path
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self.model = model
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self.model_keys = model.keys(True)
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def __getitem__(self, key):
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if key in self.model_keys:
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return self._get_formatted(self.model, key)
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else:
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raise KeyError(key)
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def __iter__(self):
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return iter(self.model_keys)
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def __len__(self):
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return len(self.model_keys)
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def get(self, key, default=None):
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if default is None:
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default = self.model._type(key).format(None)
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return super(FormattedMapping, self).get(key, default)
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def _get_formatted(self, model, key):
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value = model._type(key).format(model.get(key))
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if isinstance(value, bytes):
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value = value.decode('utf8', 'ignore')
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if self.for_path:
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sep_repl = beets.config['path_sep_replace'].get(unicode)
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for sep in (os.path.sep, os.path.altsep):
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if sep:
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value = value.replace(sep, sep_repl)
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return value
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# Abstract base for model classes.
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class Model(object):
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"""An abstract object representing an object in the database. Model
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objects act like dictionaries (i.e., the allow subscript access like
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``obj['field']``). The same field set is available via attribute
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access as a shortcut (i.e., ``obj.field``). Three kinds of attributes are
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available:
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* **Fixed attributes** come from a predetermined list of field
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names. These fields correspond to SQLite table columns and are
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thus fast to read, write, and query.
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* **Flexible attributes** are free-form and do not need to be listed
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ahead of time.
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* **Computed attributes** are read-only fields computed by a getter
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function provided by a plugin.
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Access to all three field types is uniform: ``obj.field`` works the
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same regardless of whether ``field`` is fixed, flexible, or
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computed.
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Model objects can optionally be associated with a `Library` object,
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in which case they can be loaded and stored from the database. Dirty
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flags are used to track which fields need to be stored.
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"""
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# Abstract components (to be provided by subclasses).
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_table = None
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"""The main SQLite table name.
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"""
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_flex_table = None
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"""The flex field SQLite table name.
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"""
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_fields = {}
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"""A mapping indicating available "fixed" fields on this type. The
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keys are field names and the values are `Type` objects.
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"""
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_search_fields = ()
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"""The fields that should be queried by default by unqualified query
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terms.
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"""
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_types = {}
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"""Optional Types for non-fixed (i.e., flexible and computed) fields.
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"""
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@classmethod
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def _getters(cls):
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"""Return a mapping from field names to getter functions.
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"""
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# We could cache this if it becomes a performance problem to
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# gather the getter mapping every time.
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raise NotImplementedError()
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def _template_funcs(self):
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"""Return a mapping from function names to text-transformer
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functions.
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"""
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# As above: we could consider caching this result.
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raise NotImplementedError()
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# Basic operation.
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def __init__(self, db=None, **values):
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"""Create a new object with an optional Database association and
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initial field values.
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"""
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self._db = db
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self._dirty = set()
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self._values_fixed = {}
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self._values_flex = {}
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# Initial contents.
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self.update(values)
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self.clear_dirty()
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@classmethod
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def _awaken(cls, db=None, fixed_values=None, flex_values=None):
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"""Create an object with values drawn from the database.
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This is a performance optimization: the checks involved with
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ordinary construction are bypassed.
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"""
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obj = cls(db)
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if fixed_values:
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for key, value in fixed_values.items():
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obj._values_fixed[key] = cls._fields[key].from_sql(value)
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if flex_values:
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for key, value in flex_values.items():
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if key in cls._types:
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value = cls._types[key].from_sql(value)
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obj._values_flex[key] = value
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return obj
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def __repr__(self):
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return '{0}({1})'.format(
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type(self).__name__,
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', '.join('{0}={1!r}'.format(k, v) for k, v in dict(self).items()),
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)
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def clear_dirty(self):
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"""Mark all fields as *clean* (i.e., not needing to be stored to
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the database).
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"""
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self._dirty = set()
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def _check_db(self, need_id=True):
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"""Ensure that this object is associated with a database row: it
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has a reference to a database (`_db`) and an id. A ValueError
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exception is raised otherwise.
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"""
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if not self._db:
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raise ValueError('{0} has no database'.format(type(self).__name__))
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if need_id and not self.id:
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raise ValueError('{0} has no id'.format(type(self).__name__))
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# Essential field accessors.
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@classmethod
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def _type(self, key):
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"""Get the type of a field, a `Type` instance.
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If the field has no explicit type, it is given the base `Type`,
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which does no conversion.
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"""
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return self._fields.get(key) or self._types.get(key) or BASE_TYPE
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def __getitem__(self, key):
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"""Get the value for a field. Raise a KeyError if the field is
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not available.
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"""
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getters = self._getters()
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if key in getters: # Computed.
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return getters[key](self)
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elif key in self._fields: # Fixed.
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return self._values_fixed.get(key)
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elif key in self._values_flex: # Flexible.
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return self._values_flex[key]
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else:
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raise KeyError(key)
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def __setitem__(self, key, value):
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"""Assign the value for a field.
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"""
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# Choose where to place the value.
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if key in self._fields:
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source = self._values_fixed
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else:
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source = self._values_flex
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# If the field has a type, filter the value.
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value = self._type(key).normalize(value)
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# Assign value and possibly mark as dirty.
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old_value = source.get(key)
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source[key] = value
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if old_value != value:
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self._dirty.add(key)
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def __delitem__(self, key):
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"""Remove a flexible attribute from the model.
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"""
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if key in self._values_flex: # Flexible.
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del self._values_flex[key]
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self._dirty.add(key) # Mark for dropping on store.
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elif key in self._getters(): # Computed.
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raise KeyError('computed field {0} cannot be deleted'.format(key))
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elif key in self._fields: # Fixed.
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raise KeyError('fixed field {0} cannot be deleted'.format(key))
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else:
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raise KeyError('no such field {0}'.format(key))
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def keys(self, computed=False):
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"""Get a list of available field names for this object. The
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`computed` parameter controls whether computed (plugin-provided)
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fields are included in the key list.
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"""
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base_keys = list(self._fields) + self._values_flex.keys()
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if computed:
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return base_keys + self._getters().keys()
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else:
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return base_keys
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# Act like a dictionary.
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def update(self, values):
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"""Assign all values in the given dict.
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"""
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for key, value in values.items():
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self[key] = value
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def items(self):
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"""Iterate over (key, value) pairs that this object contains.
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Computed fields are not included.
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"""
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for key in self:
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yield key, self[key]
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def get(self, key, default=None):
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"""Get the value for a given key or `default` if it does not
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exist.
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"""
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if key in self:
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return self[key]
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else:
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return default
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def __contains__(self, key):
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"""Determine whether `key` is an attribute on this object.
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"""
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return key in self.keys(True)
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def __iter__(self):
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"""Iterate over the available field names (excluding computed
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fields).
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"""
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return iter(self.keys())
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# Convenient attribute access.
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def __getattr__(self, key):
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if key.startswith('_'):
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raise AttributeError('model has no attribute {0!r}'.format(key))
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else:
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try:
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return self[key]
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except KeyError:
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raise AttributeError('no such field {0!r}'.format(key))
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def __setattr__(self, key, value):
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if key.startswith('_'):
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super(Model, self).__setattr__(key, value)
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else:
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self[key] = value
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def __delattr__(self, key):
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if key.startswith('_'):
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super(Model, self).__delattr__(key)
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else:
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del self[key]
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# Database interaction (CRUD methods).
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def store(self):
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"""Save the object's metadata into the library database.
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"""
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self._check_db()
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# Build assignments for query.
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assignments = ''
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subvars = []
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for key in self._fields:
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if key != 'id' and key in self._dirty:
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self._dirty.remove(key)
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assignments += key + '=?,'
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value = self._type(key).to_sql(self[key])
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subvars.append(value)
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assignments = assignments[:-1] # Knock off last ,
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with self._db.transaction() as tx:
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# Main table update.
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if assignments:
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query = 'UPDATE {0} SET {1} WHERE id=?'.format(
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self._table, assignments
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)
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subvars.append(self.id)
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tx.mutate(query, subvars)
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# Modified/added flexible attributes.
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for key, value in self._values_flex.items():
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if key in self._dirty:
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self._dirty.remove(key)
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tx.mutate(
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'INSERT INTO {0} '
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'(entity_id, key, value) '
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'VALUES (?, ?, ?);'.format(self._flex_table),
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(self.id, key, value),
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)
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# Deleted flexible attributes.
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for key in self._dirty:
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tx.mutate(
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'DELETE FROM {0} '
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'WHERE entity_id=? AND key=?'.format(self._flex_table),
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(self.id, key)
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)
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self.clear_dirty()
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def load(self):
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"""Refresh the object's metadata from the library database.
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"""
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self._check_db()
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stored_obj = self._db._get(type(self), self.id)
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assert stored_obj is not None, "object {0} not in DB".format(self.id)
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self._values_fixed = {}
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self._values_flex = {}
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self.update(dict(stored_obj))
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self.clear_dirty()
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def remove(self):
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"""Remove the object's associated rows from the database.
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"""
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self._check_db()
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with self._db.transaction() as tx:
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tx.mutate(
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'DELETE FROM {0} WHERE id=?'.format(self._table),
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(self.id,)
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)
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tx.mutate(
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'DELETE FROM {0} WHERE entity_id=?'.format(self._flex_table),
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(self.id,)
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)
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def add(self, db=None):
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"""Add the object to the library database. This object must be
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associated with a database; you can provide one via the `db`
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parameter or use the currently associated database.
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The object's `id` and `added` fields are set along with any
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current field values.
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"""
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if db:
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self._db = db
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self._check_db(False)
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with self._db.transaction() as tx:
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new_id = tx.mutate(
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'INSERT INTO {0} DEFAULT VALUES'.format(self._table)
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)
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self.id = new_id
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self.added = time.time()
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# Mark every non-null field as dirty and store.
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for key in self:
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if self[key] is not None:
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self._dirty.add(key)
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self.store()
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# Formatting and templating.
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_formatter = FormattedMapping
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def formatted(self, for_path=False):
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"""Get a mapping containing all values on this object formatted
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as human-readable unicode strings.
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"""
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return self._formatter(self, for_path)
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def evaluate_template(self, template, for_path=False):
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"""Evaluate a template (a string or a `Template` object) using
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the object's fields. If `for_path` is true, then no new path
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separators will be added to the template.
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"""
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# Perform substitution.
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if isinstance(template, basestring):
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template = Template(template)
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return template.substitute(self.formatted(for_path),
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self._template_funcs())
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# Parsing.
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@classmethod
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def _parse(cls, key, string):
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"""Parse a string as a value for the given key.
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"""
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if not isinstance(string, basestring):
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raise TypeError("_parse() argument must be a string")
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return cls._type(key).parse(string)
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# Database controller and supporting interfaces.
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class Results(object):
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"""An item query result set. Iterating over the collection lazily
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constructs LibModel objects that reflect database rows.
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"""
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def __init__(self, model_class, rows, db, query=None, sort=None):
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"""Create a result set that will construct objects of type
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`model_class`, which should be a subclass of `LibModel`, out of
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the query result mapping in `rows`. The new objects are
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associated with the database `db`.
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If `query` is provided, it is used as a predicate to filter the results
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for a "slow query" that cannot be evaluated by the database directly.
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If `sort` is provided, it is used to sort the full list of results
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before returning. This means it is a "slow sort" and all objects must
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be built before returning the first one.
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"""
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self.model_class = model_class
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self.rows = rows
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self.db = db
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self.query = query
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self.sort = sort
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def __iter__(self):
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"""Construct Python objects for all rows that pass the query
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predicate.
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"""
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if self.sort:
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# Slow sort. Must build the full list first.
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objects = []
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for row in self.rows:
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obj = self._make_model(row)
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# check the predicate if any
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if not self.query or self.query.match(obj):
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objects.append(obj)
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# Now that we have the full list, we can sort it
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objects = self.sort.sort(objects)
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for o in objects:
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yield o
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else:
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for row in self.rows:
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obj = self._make_model(row)
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# check the predicate if any
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if not self.query or self.query.match(obj):
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yield obj
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def _make_model(self, row):
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# Get the flexible attributes for the object.
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with self.db.transaction() as tx:
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flex_rows = tx.query(
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'SELECT * FROM {0} WHERE entity_id=?'.format(
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self.model_class._flex_table
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),
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(row['id'],)
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)
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cols = dict(row)
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values = dict((k, v) for (k, v) in cols.items()
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if not k[:4] == 'flex')
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flex_values = dict((row['key'], row['value']) for row in flex_rows)
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# Construct the Python object
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obj = self.model_class._awaken(self.db, values, flex_values)
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return obj
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def __len__(self):
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"""Get the number of matching objects.
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"""
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if self.query:
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# A slow query. Fall back to testing every object.
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count = 0
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for obj in self:
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count += 1
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return count
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else:
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# A fast query. Just count the rows.
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return len(self.rows)
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def __nonzero__(self):
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"""Does this result contain any objects?
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"""
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return bool(len(self))
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def __getitem__(self, n):
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"""Get the nth item in this result set. This is inefficient: all
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items up to n are materialized and thrown away.
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"""
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it = iter(self)
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try:
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for i in range(n):
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it.next()
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return it.next()
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except StopIteration:
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raise IndexError('result index {0} out of range'.format(n))
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def get(self):
|
|
"""Return the first matching object, or None if no objects
|
|
match.
|
|
"""
|
|
it = iter(self)
|
|
try:
|
|
return it.next()
|
|
except StopIteration:
|
|
return None
|
|
|
|
|
|
class Transaction(object):
|
|
"""A context manager for safe, concurrent access to the database.
|
|
All SQL commands should be executed through a transaction.
|
|
"""
|
|
def __init__(self, db):
|
|
self.db = db
|
|
|
|
def __enter__(self):
|
|
"""Begin a transaction. This transaction may be created while
|
|
another is active in a different thread.
|
|
"""
|
|
with self.db._tx_stack() as stack:
|
|
first = not stack
|
|
stack.append(self)
|
|
if first:
|
|
# Beginning a "root" transaction, which corresponds to an
|
|
# SQLite transaction.
|
|
self.db._db_lock.acquire()
|
|
return self
|
|
|
|
def __exit__(self, exc_type, exc_value, traceback):
|
|
"""Complete a transaction. This must be the most recently
|
|
entered but not yet exited transaction. If it is the last active
|
|
transaction, the database updates are committed.
|
|
"""
|
|
with self.db._tx_stack() as stack:
|
|
assert stack.pop() is self
|
|
empty = not stack
|
|
if empty:
|
|
# Ending a "root" transaction. End the SQLite transaction.
|
|
self.db._connection().commit()
|
|
self.db._db_lock.release()
|
|
|
|
def query(self, statement, subvals=()):
|
|
"""Execute an SQL statement with substitution values and return
|
|
a list of rows from the database.
|
|
"""
|
|
cursor = self.db._connection().execute(statement, subvals)
|
|
return cursor.fetchall()
|
|
|
|
def mutate(self, statement, subvals=()):
|
|
"""Execute an SQL statement with substitution values and return
|
|
the row ID of the last affected row.
|
|
"""
|
|
cursor = self.db._connection().execute(statement, subvals)
|
|
return cursor.lastrowid
|
|
|
|
def script(self, statements):
|
|
"""Execute a string containing multiple SQL statements."""
|
|
self.db._connection().executescript(statements)
|
|
|
|
|
|
class Database(object):
|
|
"""A container for Model objects that wraps an SQLite database as
|
|
the backend.
|
|
"""
|
|
_models = ()
|
|
"""The Model subclasses representing tables in this database.
|
|
"""
|
|
|
|
def __init__(self, path):
|
|
self.path = path
|
|
|
|
self._connections = {}
|
|
self._tx_stacks = defaultdict(list)
|
|
|
|
# A lock to protect the _connections and _tx_stacks maps, which
|
|
# both map thread IDs to private resources.
|
|
self._shared_map_lock = threading.Lock()
|
|
|
|
# A lock to protect access to the database itself. SQLite does
|
|
# allow multiple threads to access the database at the same
|
|
# time, but many users were experiencing crashes related to this
|
|
# capability: where SQLite was compiled without HAVE_USLEEP, its
|
|
# backoff algorithm in the case of contention was causing
|
|
# whole-second sleeps (!) that would trigger its internal
|
|
# timeout. Using this lock ensures only one SQLite transaction
|
|
# is active at a time.
|
|
self._db_lock = threading.Lock()
|
|
|
|
# Set up database schema.
|
|
for model_cls in self._models:
|
|
self._make_table(model_cls._table, model_cls._fields)
|
|
self._make_attribute_table(model_cls._flex_table)
|
|
|
|
# Primitive access control: connections and transactions.
|
|
|
|
def _connection(self):
|
|
"""Get a SQLite connection object to the underlying database.
|
|
One connection object is created per thread.
|
|
"""
|
|
thread_id = threading.current_thread().ident
|
|
with self._shared_map_lock:
|
|
if thread_id in self._connections:
|
|
return self._connections[thread_id]
|
|
else:
|
|
# Make a new connection.
|
|
conn = sqlite3.connect(
|
|
self.path,
|
|
timeout=beets.config['timeout'].as_number(),
|
|
)
|
|
|
|
# Access SELECT results like dictionaries.
|
|
conn.row_factory = sqlite3.Row
|
|
|
|
self._connections[thread_id] = conn
|
|
return conn
|
|
|
|
@contextlib.contextmanager
|
|
def _tx_stack(self):
|
|
"""A context manager providing access to the current thread's
|
|
transaction stack. The context manager synchronizes access to
|
|
the stack map. Transactions should never migrate across threads.
|
|
"""
|
|
thread_id = threading.current_thread().ident
|
|
with self._shared_map_lock:
|
|
yield self._tx_stacks[thread_id]
|
|
|
|
def transaction(self):
|
|
"""Get a :class:`Transaction` object for interacting directly
|
|
with the underlying SQLite database.
|
|
"""
|
|
return Transaction(self)
|
|
|
|
# Schema setup and migration.
|
|
|
|
def _make_table(self, table, fields):
|
|
"""Set up the schema of the database. `fields` is a mapping
|
|
from field names to `Type`s. Columns are added if necessary.
|
|
"""
|
|
# Get current schema.
|
|
with self.transaction() as tx:
|
|
rows = tx.query('PRAGMA table_info(%s)' % table)
|
|
current_fields = set([row[1] for row in rows])
|
|
|
|
field_names = set(fields.keys())
|
|
if current_fields.issuperset(field_names):
|
|
# Table exists and has all the required columns.
|
|
return
|
|
|
|
if not current_fields:
|
|
# No table exists.
|
|
columns = []
|
|
for name, typ in fields.items():
|
|
columns.append('{0} {1}'.format(name, typ.sql))
|
|
setup_sql = 'CREATE TABLE {0} ({1});\n'.format(table,
|
|
', '.join(columns))
|
|
|
|
else:
|
|
# Table exists does not match the field set.
|
|
setup_sql = ''
|
|
for name, typ in fields.items():
|
|
if name in current_fields:
|
|
continue
|
|
setup_sql += 'ALTER TABLE {0} ADD COLUMN {1} {2};\n'.format(
|
|
table, name, typ.sql
|
|
)
|
|
|
|
with self.transaction() as tx:
|
|
tx.script(setup_sql)
|
|
|
|
def _make_attribute_table(self, flex_table):
|
|
"""Create a table and associated index for flexible attributes
|
|
for the given entity (if they don't exist).
|
|
"""
|
|
with self.transaction() as tx:
|
|
tx.script("""
|
|
CREATE TABLE IF NOT EXISTS {0} (
|
|
id INTEGER PRIMARY KEY,
|
|
entity_id INTEGER,
|
|
key TEXT,
|
|
value NONE,
|
|
UNIQUE(entity_id, key) ON CONFLICT REPLACE);
|
|
CREATE INDEX IF NOT EXISTS {0}_by_entity
|
|
ON {0} (entity_id);
|
|
""".format(flex_table))
|
|
|
|
# Querying.
|
|
|
|
def _fetch(self, model_cls, query, sort=None):
|
|
"""Fetch the objects of type `model_cls` matching the given
|
|
query. The query may be given as a string, string sequence, a
|
|
Query object, or None (to fetch everything). `sort` is an
|
|
optional Sort object.
|
|
"""
|
|
where, subvals = query.clause()
|
|
sort = sort or NullSort()
|
|
order_by = sort.order_clause()
|
|
|
|
sql = ("SELECT * FROM {0} WHERE {1} {2}").format(
|
|
model_cls._table,
|
|
where or '1',
|
|
"ORDER BY {0}".format(order_by) if order_by else '',
|
|
)
|
|
|
|
with self.transaction() as tx:
|
|
rows = tx.query(sql, subvals)
|
|
|
|
return Results(
|
|
model_cls, rows, self,
|
|
None if where else query, # Slow query component.
|
|
sort if sort.is_slow() else None, # Slow sort component.
|
|
)
|
|
|
|
def _get(self, model_cls, id):
|
|
"""Get a Model object by its id or None if the id does not
|
|
exist.
|
|
"""
|
|
return self._fetch(model_cls, MatchQuery('id', id)).get()
|