fleche.caches

Attributes

logger
DigestedIterable
DigestedDict

Exceptions

Rejected

Cache refused to cache the call for some reason or other.

Classes

BaseCache	Helper class that provides a standard way to create an ABC using
Cache	Helper class that provides a standard way to create an ABC using
CacheWrapper	Forwarding base class: all BaseCache methods delegate to self.cache.
ReadOnlyMixin	Raises Rejected for save and evict.
ReadOnlyCache	A cache that can only be read from.
FilteringMixin	Filters load and _query results by a predicate.
FilteredCache	A read-only view of a cache that only exposes calls matching a predicate.
RefreshingCache	A cache that forces re-execution by always missing on load.
CacheStack	Represents a combination of caches.
SizeLimitedMixin	Mixin that enforces a maximum number of cached calls with random eviction.
SizeLimitedCache	A Cache that enforces a maximum number of cached calls.

Functions

_combine_expand(→ fleche.digest.Digest)	Reduce sub-storage expand results to a single resolved digest.
_combine_shrink(→ fleche.digest.Digest)	Reduce sub-storage shrink results to the longest (safest) prefix.

Module Contents

fleche.caches.logger

exception fleche.caches.Rejected

Bases: Exception

Cache refused to cache the call for some reason or other.

fleche.caches.DigestedIterable

fleche.caches.DigestedDict

class fleche.caches.BaseCache

Bases: abc.ABC

Helper class that provides a standard way to create an ABC using inheritance.

abstractmethod save(call: fleche.call.Call) → str

abstractmethod load(key: str) → fleche.call.LazyCall

abstractmethod load_value(key: str) → Any

abstractmethod evict(key: str | fleche.digest.Digest) → None

contains(key: str) → bool

transfer(other: BaseCache, pop: bool = False, overwrite: bool = False) → None

Transfer all calls from this cache to another cache.

Parameters:

• other – The destination cache.

• pop – If True, evict transferred keys from the source cache after moving.

• overwrite – If True, overwrite existing entries in the target cache. If False (default), skip entries that already exist in the target.

readonly() → ReadOnlyCache

Return a read-only view of this cache.

push(cache: BaseCache) → CacheStack

abstractmethod expand(key: fleche.digest.Digest | str) → fleche.digest.Digest

Expand a short digest prefix to its full-length digest.

Parameters:

key (str or Digest) – the short digest prefix to expand

Returns:

the full-length digest

Return type:

Digest

Raises:

• KeyError – if the key is not found

• AmbiguousDigestError – if the prefix matches more than one entry

abstractmethod shrink(key: fleche.digest.Digest | str) → fleche.digest.Digest

Find the shortest substring that is still an unambigious reference to the same call.

Warning

This is a property of how many values there are in your storage! A key returned from this function may become ambigious in the future when more values are added. Do not rely on this function in your programs, it is provided as a convenience for users only!

Parameters:

key (str or Digest) – the key to shorten

Returns:

shortest key possible

Return type:

Digest

Raises:

AmbiguousDigestError – if no shorter key is possible

abstractmethod _query(call: BaseCache._query.call) → Iterable[fleche.call.LazyCall]

query(template: fleche.call.QueryCall | None = None, **kwargs) → fleche.query.QueryIterator

Query the cache for matching calls.

Accepts either a QueryCall as the first positional argument, or the same keyword arguments that QueryCall accepts. Omitted fields default to None (wildcard). Passing both a template and keyword arguments raises TypeError.

Examples:

cache.query(name="my_func")
cache.query(name="my_func", arguments={"x": 1})
cache.query(QueryCall(name="my_func"))  # existing form still works
cache.query()  # all calls

Returns:

QueryIterator

table(arguments: Iterable[str] | str | Literal[True] = (), results=False) → pandas.DataFrame

Return a pandas DataFrame summarizing cached calls via query().

This implementation uses a fully-wildcard Call template to retrieve all calls through self.query and then flattens metadata keys into top-level columns for convenience.

By default, arguments and results are elided.

The DataFrame index will be the lookup key (digest) of each call. Columns are:

• name: the function name

• module: the module name

• ‘result`: if results argument is True

• metadata fields are flattened and added as columns directly

If given argument names collide with any of the above columns, they are prefixed by ‘a_’. Only requested arguments are loaded from cache.

Parameters:

• arguments – add the given arguments (of the queried calls) as columns to the table. Pass True to add all arguments, or a single string as a shortcut for a one-element tuple.

• results (bool) – if True, add results of queried calls to table

Returns:

table of all calls on cache

Return type:

pandas.DataFrame

filter(predicate: Callable[[fleche.call.Call | fleche.call.LazyCall], bool] | fleche.call.QueryCall) → FilteredCache

Create a read-only view of this cache that only exposes calls matching the predicate.

Parameters:

predicate – A function that takes a Call or LazyCall and returns True if it should be included in the new cache, or a QueryCall object to use as a template.

Returns:

A read-only view of the cache.

Return type:

FilteredCache

fleche.caches._combine_expand(key: Digest | str, results: Iterable[Digest]) → fleche.digest.Digest

Reduce sub-storage expand results to a single resolved digest.

Raises:

• KeyError – if no results were found.

• AmbiguousDigestError – if results disagree on the full digest.

fleche.caches._combine_shrink(key: Digest | str, results: Iterable[Digest]) → fleche.digest.Digest

Reduce sub-storage shrink results to the longest (safest) prefix.

Raises:

KeyError – if no results were found.

class fleche.caches.Cache

Bases: BaseCache

Helper class that provides a standard way to create an ABC using inheritance.

values: fleche.storage.ValueStorage

calls: fleche.storage.CallStorage

load_value(key)

save(call: fleche.call.Call) → str

load(key: str) → fleche.call.LazyCall

contains(key: str) → bool

expand(key: fleche.digest.Digest | str) → fleche.digest.Digest

Expand a short digest prefix to its full-length digest.

Parameters:

key (str or Digest) – the short digest prefix to expand

Returns:

the full-length digest

Return type:

Digest

Raises:

• KeyError – if the key is not found

• AmbiguousDigestError – if the prefix matches more than one entry

shrink(key: fleche.digest.Digest | str) → fleche.digest.Digest

Find the shortest substring that is still an unambigious reference to the same call.

Warning

This is a property of how many values there are in your storage! A key returned from this function may become ambigious in the future when more values are added. Do not rely on this function in your programs, it is provided as a convenience for users only!

Parameters:

key (str or Digest) – the key to shorten

Returns:

shortest key possible

Return type:

Digest

Raises:

AmbiguousDigestError – if no shorter key is possible

_query(call: Cache._query.call) → Iterable[fleche.call.LazyCall]

Query for cached calls that match a template and return decoded results.

This delegates to the underlying CallStorage.query() using the provided template call. Any digested argument values and the result are decoded via this cache’s value storage before yielding.

Parameters:

call – A Call instance used as a template; fields set to None act as wildcards. For arguments and result, comparisons follow digest semantics (i.e., values are matched by their digest).

Yields:

Call | LazyCall – Matching calls with arguments and result decoded from digests where possible.

evict(key: str | fleche.digest.Digest) → None

redigest() → None

Ensures consistent cache keys in case digest function changed.

This may take time depending on cache size.

gc() → set[fleche.digest.Digest]

Evict value entries not reachable from any stored call.

Brute-force mark-and-sweep: walks every call record to build the set of directly-referenced value digests, then transitively follows destructured sub-references (via DestructuringMixin.child_digests() on storages that satisfy HasChildDigests), and evicts every values key outside the reachable set. Call records are left untouched.

Returns:

The set of digests that were evicted from value storage.

class fleche.caches.CacheWrapper

Bases: BaseCache

Forwarding base class: all BaseCache methods delegate to self.cache.

Combine with behaviour mixins (ReadOnlyMixin, FilteringMixin) to build concrete wrapper classes without redeclaring cache.

cache: BaseCache

save(call: fleche.call.Call) → str

load(key: str) → fleche.call.LazyCall

load_value(key: str) → Any

contains(key: str) → bool

evict(key: str | fleche.digest.Digest) → None

expand(key: fleche.digest.Digest | str) → fleche.digest.Digest

Expand a short digest prefix to its full-length digest.

Parameters:

key (str or Digest) – the short digest prefix to expand

Returns:

the full-length digest

Return type:

Digest

Raises:

• KeyError – if the key is not found

• AmbiguousDigestError – if the prefix matches more than one entry

shrink(key: fleche.digest.Digest | str) → fleche.digest.Digest

Find the shortest substring that is still an unambigious reference to the same call.

Warning

This is a property of how many values there are in your storage! A key returned from this function may become ambigious in the future when more values are added. Do not rely on this function in your programs, it is provided as a convenience for users only!

Parameters:

key (str or Digest) – the key to shorten

Returns:

shortest key possible

Return type:

Digest

Raises:

AmbiguousDigestError – if no shorter key is possible

_query(call: CacheWrapper._query.call) → Iterable[fleche.call.LazyCall]

class fleche.caches.ReadOnlyMixin

Bases: CacheWrapper

Raises Rejected for save and evict.

save(call: fleche.call.Call)

evict(key: str | fleche.digest.Digest) → None

class fleche.caches.ReadOnlyCache

Bases: ReadOnlyMixin

A cache that can only be read from.

class fleche.caches.FilteringMixin

Bases: CacheWrapper

Filters load and _query results by a predicate.

predicate: Callable[[fleche.call.Call | fleche.call.LazyCall], bool]

load(key: str) → fleche.call.LazyCall

_query(call: FilteringMixin._query.call) → Iterable[fleche.call.LazyCall]

class fleche.caches.FilteredCache

Bases: FilteringMixin, ReadOnlyMixin

A read-only view of a cache that only exposes calls matching a predicate.

class fleche.caches.RefreshingCache

Bases: CacheWrapper

A cache that forces re-execution by always missing on load.

It forwards saves and value loads to an underlying cache, allowing new results to be stored while ensuring that existing ones are ignored for the duration of its use.

This is necessary to handle nested fleche calls during a rerun, otherwise forcing them to re-execute would be awkward.

load(key: str) → fleche.call.LazyCall

contains(key: str) → bool

class fleche.caches.CacheStack

Bases: BaseCache

Represents a combination of caches.

Saving will always hit the lowest level, while loading will traverse up.

stack: tuple[BaseCache, Ellipsis]

__post_init__()

save(call: fleche.call.Call)

load(key) → fleche.call.LazyCall

load_value(key)

contains(key: str) → bool

push(cache: BaseCache) → CacheStack

evict(key: str | fleche.digest.Digest) → None

expand(key: fleche.digest.Digest | str) → fleche.digest.Digest

Expand a short digest prefix to its full-length digest.

Parameters:

key (str or Digest) – the short digest prefix to expand

Returns:

the full-length digest

Return type:

Digest

Raises:

• KeyError – if the key is not found

• AmbiguousDigestError – if the prefix matches more than one entry

shrink(key: fleche.digest.Digest | str) → fleche.digest.Digest

Find the shortest substring that is still an unambigious reference to the same call.

Warning

This is a property of how many values there are in your storage! A key returned from this function may become ambigious in the future when more values are added. Do not rely on this function in your programs, it is provided as a convenience for users only!

Parameters:

key (str or Digest) – the key to shorten

Returns:

shortest key possible

Return type:

Digest

Raises:

AmbiguousDigestError – if no shorter key is possible

_query(call: CacheStack._query.call) → Iterable[fleche.call.LazyCall]

Aggregate query results across the stack, avoiding duplicates.

The caches are queried from bottom to top. Results are deduplicated by their lookup key (via Call.to_lookup_key()) and yielded in the order they are first seen.

Parameters:

call – A template Call where None fields act as wildcards.

Yields:

Call | LazyCall – Matching calls from any cache in the stack, without duplicates.

class fleche.caches.SizeLimitedMixin

Bases: BaseCache

Mixin that enforces a maximum number of cached calls with random eviction.

Combine this with Cache (mixin first in MRO) to get a size-limited cache:

@dataclass
class SizeLimitedCache(SizeLimitedMixin, Cache):
    max_size: int

When a new call is saved and the number of cached calls exceeds max_size, a call record is selected for eviction via _pick_eviction_target(). Value storage is intentionally left untouched.

The concrete class must provide a max_size integer, which is provided automatically when mixed with Cache.

max_size: int

_lock: threading.RLock

_keys: set[str]

__post_init__(*args, **kwargs)

_pick_eviction_target(keys: list[str]) → str

Select the call to evict from a sample of cached call keys.

The default implementation chooses uniformly at random. Override this method to implement a different eviction policy without touching any other part of the class.

Parameters:

keys – A non-empty list of all tracked call keys.

Returns:

The key of the call that should be evicted.

_enforce_size_limit() → None

Evict call records until the cache is within max_size.

save(call: SizeLimitedMixin.save.call) → str

evict(key: str | fleche.digest.Digest) → None

class fleche.caches.SizeLimitedCache

Bases: SizeLimitedMixin, Cache

A Cache that enforces a maximum number of cached calls.

When a new call is saved and the number of cached calls exceeds max_size, a call record is selected for eviction via _pick_eviction_target(). The default policy evicts uniformly at random; override _pick_eviction_target() to change this.

Parameters:

• values – Value storage (forwarded to Cache).

• _calls – Call storage (forwarded to Cache).

• max_size – Maximum number of calls to keep.

max_size: int