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Prevent sqlalchemy Transparent SQL Compilation Caching from filling u…
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…p during purge (home-assistant#71015)
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@bdraco @balloob
bdraco authored and balloob committed Apr 29, 2022
1 parent c52ad6e commit 0b144be
Showing 1 changed file with 246 additions and 15 deletions.
261 changes: 246 additions & 15 deletions homeassistant/components/recorder/purge.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,15 @@

from collections.abc import Callable, Iterable
from datetime import datetime
from itertools import zip_longest
import logging
from typing import TYPE_CHECKING

from sqlalchemy import column, func, select, union
from sqlalchemy import func, lambda_stmt, select, union_all
from sqlalchemy.orm.session import Session
from sqlalchemy.sql.expression import distinct
from sqlalchemy.sql.lambdas import StatementLambdaElement
from sqlalchemy.sql.selectable import Select

from homeassistant.const import EVENT_STATE_CHANGED

Expand Down Expand Up @@ -112,6 +115,223 @@ def _select_event_state_and_attributes_ids_to_purge(
return event_ids, state_ids, attributes_ids


def _state_attrs_exist(attr: int | None) -> Select:
"""Check if a state attributes id exists in the states table."""
return select(func.min(States.attributes_id)).where(States.attributes_id == attr)


def _generate_find_attr_lambda(
attr1: int,
attr2: int | None,
attr3: int | None,
attr4: int | None,
attr5: int | None,
attr6: int | None,
attr7: int | None,
attr8: int | None,
attr9: int | None,
attr10: int | None,
attr11: int | None,
attr12: int | None,
attr13: int | None,
attr14: int | None,
attr15: int | None,
attr16: int | None,
attr17: int | None,
attr18: int | None,
attr19: int | None,
attr20: int | None,
attr21: int | None,
attr22: int | None,
attr23: int | None,
attr24: int | None,
attr25: int | None,
attr26: int | None,
attr27: int | None,
attr28: int | None,
attr29: int | None,
attr30: int | None,
attr31: int | None,
attr32: int | None,
attr33: int | None,
attr34: int | None,
attr35: int | None,
attr36: int | None,
attr37: int | None,
attr38: int | None,
attr39: int | None,
attr40: int | None,
attr41: int | None,
attr42: int | None,
attr43: int | None,
attr44: int | None,
attr45: int | None,
attr46: int | None,
attr47: int | None,
attr48: int | None,
attr49: int | None,
attr50: int | None,
attr51: int | None,
attr52: int | None,
attr53: int | None,
attr54: int | None,
attr55: int | None,
attr56: int | None,
attr57: int | None,
attr58: int | None,
attr59: int | None,
attr60: int | None,
attr61: int | None,
attr62: int | None,
attr63: int | None,
attr64: int | None,
attr65: int | None,
attr66: int | None,
attr67: int | None,
attr68: int | None,
attr69: int | None,
attr70: int | None,
attr71: int | None,
attr72: int | None,
attr73: int | None,
attr74: int | None,
attr75: int | None,
attr76: int | None,
attr77: int | None,
attr78: int | None,
attr79: int | None,
attr80: int | None,
attr81: int | None,
attr82: int | None,
attr83: int | None,
attr84: int | None,
attr85: int | None,
attr86: int | None,
attr87: int | None,
attr88: int | None,
attr89: int | None,
attr90: int | None,
attr91: int | None,
attr92: int | None,
attr93: int | None,
attr94: int | None,
attr95: int | None,
attr96: int | None,
attr97: int | None,
attr98: int | None,
attr99: int | None,
attr100: int | None,
) -> StatementLambdaElement:
"""Generate the find attributes select only once.
https://docs.sqlalchemy.org/en/14/core/connections.html#quick-guidelines-for-lambdas
"""
return lambda_stmt(
lambda: union_all(
_state_attrs_exist(attr1),
_state_attrs_exist(attr2),
_state_attrs_exist(attr3),
_state_attrs_exist(attr4),
_state_attrs_exist(attr5),
_state_attrs_exist(attr6),
_state_attrs_exist(attr7),
_state_attrs_exist(attr8),
_state_attrs_exist(attr9),
_state_attrs_exist(attr10),
_state_attrs_exist(attr11),
_state_attrs_exist(attr12),
_state_attrs_exist(attr13),
_state_attrs_exist(attr14),
_state_attrs_exist(attr15),
_state_attrs_exist(attr16),
_state_attrs_exist(attr17),
_state_attrs_exist(attr18),
_state_attrs_exist(attr19),
_state_attrs_exist(attr20),
_state_attrs_exist(attr21),
_state_attrs_exist(attr22),
_state_attrs_exist(attr23),
_state_attrs_exist(attr24),
_state_attrs_exist(attr25),
_state_attrs_exist(attr26),
_state_attrs_exist(attr27),
_state_attrs_exist(attr28),
_state_attrs_exist(attr29),
_state_attrs_exist(attr30),
_state_attrs_exist(attr31),
_state_attrs_exist(attr32),
_state_attrs_exist(attr33),
_state_attrs_exist(attr34),
_state_attrs_exist(attr35),
_state_attrs_exist(attr36),
_state_attrs_exist(attr37),
_state_attrs_exist(attr38),
_state_attrs_exist(attr39),
_state_attrs_exist(attr40),
_state_attrs_exist(attr41),
_state_attrs_exist(attr42),
_state_attrs_exist(attr43),
_state_attrs_exist(attr44),
_state_attrs_exist(attr45),
_state_attrs_exist(attr46),
_state_attrs_exist(attr47),
_state_attrs_exist(attr48),
_state_attrs_exist(attr49),
_state_attrs_exist(attr50),
_state_attrs_exist(attr51),
_state_attrs_exist(attr52),
_state_attrs_exist(attr53),
_state_attrs_exist(attr54),
_state_attrs_exist(attr55),
_state_attrs_exist(attr56),
_state_attrs_exist(attr57),
_state_attrs_exist(attr58),
_state_attrs_exist(attr59),
_state_attrs_exist(attr60),
_state_attrs_exist(attr61),
_state_attrs_exist(attr62),
_state_attrs_exist(attr63),
_state_attrs_exist(attr64),
_state_attrs_exist(attr65),
_state_attrs_exist(attr66),
_state_attrs_exist(attr67),
_state_attrs_exist(attr68),
_state_attrs_exist(attr69),
_state_attrs_exist(attr70),
_state_attrs_exist(attr71),
_state_attrs_exist(attr72),
_state_attrs_exist(attr73),
_state_attrs_exist(attr74),
_state_attrs_exist(attr75),
_state_attrs_exist(attr76),
_state_attrs_exist(attr77),
_state_attrs_exist(attr78),
_state_attrs_exist(attr79),
_state_attrs_exist(attr80),
_state_attrs_exist(attr81),
_state_attrs_exist(attr82),
_state_attrs_exist(attr83),
_state_attrs_exist(attr84),
_state_attrs_exist(attr85),
_state_attrs_exist(attr86),
_state_attrs_exist(attr87),
_state_attrs_exist(attr88),
_state_attrs_exist(attr89),
_state_attrs_exist(attr90),
_state_attrs_exist(attr91),
_state_attrs_exist(attr92),
_state_attrs_exist(attr93),
_state_attrs_exist(attr94),
_state_attrs_exist(attr95),
_state_attrs_exist(attr96),
_state_attrs_exist(attr97),
_state_attrs_exist(attr98),
_state_attrs_exist(attr99),
_state_attrs_exist(attr100),
)
)


def _select_unused_attributes_ids(
session: Session, attributes_ids: set[int], using_sqlite: bool
) -> set[int]:
Expand All @@ -132,9 +352,12 @@ def _select_unused_attributes_ids(
# > explain select distinct attributes_id from states where attributes_id in (136723);
# ...Using index
#
id_query = session.query(distinct(States.attributes_id)).filter(
States.attributes_id.in_(attributes_ids)
)
seen_ids = {
state[0]
for state in session.query(distinct(States.attributes_id))
.filter(States.attributes_id.in_(attributes_ids))
.all()
}
else:
#
# This branch is for DBMS that cannot optimize the distinct query well and has to examine
Expand All @@ -151,17 +374,25 @@ def _select_unused_attributes_ids(
# > explain select min(attributes_id) from states where attributes_id = 136723;
# ...Select tables optimized away
#
id_query = session.query(column("id")).from_statement(
union(
*[
select(func.min(States.attributes_id).label("id")).where(
States.attributes_id == attributes_id
)
for attributes_id in attributes_ids
]
)
)
to_remove = attributes_ids - {state[0] for state in id_query.all()}
# We used to generate a query based on how many attribute_ids to find but
# that meant sqlalchemy Transparent SQL Compilation Caching was working against
# us by cached up to MAX_ROWS_TO_PURGE different statements which could be
# up to 500MB for large database due to the complexity of the ORM objects.
#
# We now break the query into groups of 100 and use a lambda_stmt to ensure
# that the query is only cached once.
#
seen_ids = set()
groups = [iter(attributes_ids)] * 100
for attr_ids in zip_longest(*groups, fillvalue=None):
seen_ids |= {
state[0]
for state in session.execute(
_generate_find_attr_lambda(*attr_ids)
).all()
if state[0] is not None
}
to_remove = attributes_ids - seen_ids
_LOGGER.debug(
"Selected %s shared attributes to remove",
len(to_remove),
Expand Down

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